{"id":29743,"date":"2025-04-20T12:21:08","date_gmt":"2025-04-20T04:21:08","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/29743.html"},"modified":"2025-04-20T12:21:08","modified_gmt":"2025-04-20T04:21:08","slug":"%e3%80%90linux%e3%80%91%e3%80%90%e7%bd%91%e7%bb%9c%e3%80%91udp%e6%89%93%e6%b4%9e-%ef%bc%9e%e4%b8%8d%e5%90%8c%e5%ad%90%e7%bd%91%e4%b8%8b%e7%9a%84%e5%ae%a2%e6%88%b7%e7%ab%af%e5%92%8c%e6%9c%8d%e5%8a%a1-2","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/29743.html","title":{"rendered":"\u3010Linux\u3011\u3010\u7f51\u7edc\u3011UDP\u6253\u6d1e--\uff1e\u4e0d\u540c\u5b50\u7f51\u4e0b\u7684\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u901a\u4fe1\uff08\u672a\u6210\u529f\u7248\uff09"},"content":{"rendered":"<h2>\u3010Linux\u3011\u3010\u7f51\u7edc\u3011UDP\u6253\u6d1e\u2013&gt;\u4e0d\u540c\u5b50\u7f51\u4e0b\u7684\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u901a\u4fe1&#xff08;\u672a\u6210\u529f\u7248&#xff09;<\/h2>\n<p>\u4e0a\u6b21\u8bf4\u57fa\u4e8eUDP\u7684\u6253\u6d1e\u7a0b\u5e8f\u6539\u4e86\u4e94\u7248\u4e00\u76f4\u6ca1\u6709\u6210\u529f&#xff0c;\u8981\u5199\u4e00\u4e0b\u95ee\u9898\u6240\u5728&#xff0c;\u4f46\u662f\u6211\u540e\u7eed\u53c8\u67e5\u8be2\u4e86\u4e00\u4e9b\u8d44\u6599&#xff0c;\u6210\u529f\u5b9e\u73b0\u4e86&#xff0c;\u8fd9\u6b21\u5148\u5199\u4e00\u4e0b\u672a\u6210\u529f\u7684\u903b\u8f91&#xff0c;\u6211\u8ba4\u4e3a\u672a\u6210\u529f\u7684\u6392\u67e5\u9519\u8bef\u7684\u90e8\u5206\u4e5f\u5f88\u91cd\u8981&#xff0c;\u5982\u679c\u60f3\u76f4\u63a5\u770b\u6210\u529f\u7684\u53ef\u4ee5\u76f4\u63a5\u770b\u6211\u7684\u4e0b\u4e00\u7bc7\u6587\u7ae0\u3002<\/p>\n<p>\u9996\u5148 \u57fa\u4e8e\u4e0a\u7bc7\u6587\u7ae0\u7684UDP\u6253\u6d1e\u903b\u8f91 \u8fd9\u91cc\u76f4\u63a5\u5c06\u56fe\u8d34\u51fa\u6765&#xff1a; <img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042105-6804763187358.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/> \u6211\u7684\u903b\u8f91\u601d\u8def&#xff1a;&#xff08;ps:\u4f1a\u628a\u4ee3\u7801\u8d34\u5230\u6700\u540e\u9762\u3002)<\/p>\n<h3>\u903b\u8f91\u68b3\u7406<\/h3>\n<h4>1 \u670d\u52a1\u5668\u7aef&#xff08;server.c&#xff09;<\/h4>\n<li>\u76d1\u542c\u4e0e\u63a5\u6536\u6ce8\u518c\n<ul>\n<li>\u670d\u52a1\u5668\u521b\u5efa UDP \u5957\u63a5\u5b57\u5e76\u7ed1\u5b9a\u5230\u56fa\u5b9a\u7aef\u53e3&#xff08;5050&#xff09;\u3002<\/li>\n<li>\u4f9d\u6b21\u8c03\u7528 recvfrom() \u63a5\u6536\u4e24\u4e2a\u5ba2\u6237\u7aef&#xff08;\u5148\u540e\u4e3a C1 \u548c C2&#xff09;\u7684\u6ce8\u518c\u6d88\u606f&#xff0c;\u83b7\u53d6\u5404\u81ea\u7684\u6e90\u5730\u5740&#xff08;\u5373 NAT \u6620\u5c04\u540e\u7684\u516c\u7f51 IP \u548c\u7aef\u53e3&#xff09;\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\u5730\u5740\u4ea4\u6362\n<ul>\n<li>\u670d\u52a1\u5668\u628a C2 \u7684\u516c\u7f51\u5730\u5740&#xff08;IP \u548c\u7aef\u53e3&#xff09;\u683c\u5f0f\u5316\u6210\u5b57\u7b26\u4e32&#xff08;\u7528\u201c^\u201d\u5206\u9694&#xff09;\u53d1\u9001\u7ed9 C1\u3002<\/li>\n<li>\u540c\u6837\u628a C1 \u7684\u5730\u5740\u53d1\u9001\u7ed9 C2\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\u540e\u7eed\u5904\u7406\n<ul>\n<li>\u670d\u52a1\u5668\u5b8c\u6210\u5730\u5740\u4ea4\u6362\u540e\u9000\u51fa&#xff08;\u6ca1\u6709\u989d\u5916\u53d1\u9001\u63a2\u6d4b\u5305&#xff09;\u3002<\/li>\n<\/ul>\n<\/li>\n<hr \/>\n<h4>\u5ba2\u6237\u7aef C1&#xff08;UDPClientcc1.c&#xff09;<\/h4>\n<li>\u4e24\u4e2a\u5957\u63a5\u5b57\n<ul>\n<li>\u4f7f\u7528\u4e00\u4e2a\u5957\u63a5\u5b57&#xff08;sockS&#xff09;\u4e0e\u670d\u52a1\u5668\u901a\u4fe1&#xff0c;\u53e6\u4e00\u4e2a&#xff08;sockC&#xff09;\u7528\u4e8e\u540e\u7eed\u5bf9\u7b49\u901a\u4fe1&#xff0c;\u5e76\u7ed1\u5b9a\u5230\u56fa\u5b9a\u7aef\u53e3&#xff08;6003&#xff09;\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\u6ce8\u518c\u9636\u6bb5\n<ul>\n<li>C1 \u5411\u670d\u52a1\u5668\u53d1\u9001\u6ce8\u518c\u6d88\u606f&#xff08;\u201cI am C1\u201d&#xff09;\u3002<\/li>\n<li>\u63a5\u6536\u670d\u52a1\u5668\u8fd4\u56de\u7684\u5b57\u7b26\u4e32&#xff0c;\u89e3\u6790\u51fa\u5bf9\u65b9\u5730\u5740\u4fe1\u606f&#xff08;\u683c\u5f0f \u201cip^port\u201d&#xff09;&#xff0c;\u5b58\u5165 oppositeSideAddr\u3002<\/li>\n<\/ul>\n<\/li>\n<li>P2P \u4ea4\u4e92\u5faa\u73af\n<ul>\n<li>\u5728\u5faa\u73af\u4e2d&#xff0c;\u6bcf\u9694 500ms \u4f7f\u7528 sockC \u5411 oppositeSideAddr \u53d1\u9001\u6570\u636e&#xff08;keep-alive\/\u6d88\u606f&#xff09;&#xff0c;\u5e76\u5c1d\u8bd5\u63a5\u6536\u5bf9\u65b9\u56de\u590d\u3002<\/li>\n<\/ul>\n<\/li>\n<hr \/>\n<h4>\u5ba2\u6237\u7aef C2&#xff08;UDPClientcc2.c&#xff09;<\/h4>\n<li>\u903b\u8f91\u4e0e C1 \u7c7b\u4f3c\n<ul>\n<li>\u4f7f\u7528\u4e24\u4e2a\u5957\u63a5\u5b57&#xff0c;\u4e00\u4e2a\u4e0e\u670d\u52a1\u5668\u901a\u4fe1&#xff08;sockS&#xff09;&#xff0c;\u4e00\u4e2a\u7528\u4e8e P2P&#xff08;sockC&#xff09;&#xff0c;\u7ed1\u5b9a\u56fa\u5b9a\u7aef\u53e3&#xff08;6002&#xff09;\u3002<\/li>\n<li>\u5411\u670d\u52a1\u5668\u53d1\u9001\u6ce8\u518c\u6d88\u606f&#xff08;\u201cI am C2\u201d&#xff09;&#xff0c;\u63a5\u6536\u5e76\u89e3\u6790\u670d\u52a1\u5668\u8fd4\u56de\u7684\u5bf9\u65b9\u5730\u5740\u4fe1\u606f&#xff0c;\u5b58\u5165 oppositeSideAddr\u3002<\/li>\n<li>\u8fdb\u5165\u5faa\u73af&#xff0c;\u6bcf\u9694 500ms \u5411 oppositeSideAddr \u53d1\u9001\u6570\u636e&#xff0c;\u5e76\u7b49\u5f85\u56de\u590d\u3002<\/li>\n<\/ul>\n<\/li>\n<hr \/>\n<h3>\u6267\u884c\u7ed3\u679c<\/h3>\n<p>\u670d\u52a1\u5668&#xff1a; <img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042105-68047631e12fc.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/><\/p>\n<p>\u5ba2\u6237\u7aefc1: <img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042106-680476321a396.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/> \u5ba2\u6237\u7aefc2: <img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042106-6804763264398.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/><\/p>\n<p>\u53ef\u4ee5\u770b\u5230c1,c2 \u4e00\u76f4\u5728\u5411\u4ece\u670d\u52a1\u5668\u83b7\u53d6\u7684\u516c\u7f51ip\u548c\u7aef\u53e3\u53d1\u9001\u6570\u636e \u4f46\u662f\u4e00\u76f4\u672a\u6536\u5230\u5bf9\u7aef\u56de\u590d\u3002 \u670d\u52a1\u5668\u5728\u5411\u53cc\u65b9\u53d1\u9001\u6570\u636e\u540e\u5c31\u76f4\u63a5\u9000\u51fa\u4e86\u3002<\/p>\n<h3>\u6392\u67e5\u95ee\u9898&#xff1a;<\/h3>\n<p>\u8003\u8651\u53ef\u80fd\u5b58\u5728\u7684\u95ee\u9898\u5e76\u9010\u6b65\u6392\u67e5&#xff1a;<\/p>\n<li>\u670d\u52a1\u5668\u914d\u7f6e\u95ee\u9898\n<ul>\n<li>\u786e\u4fdd\u670d\u52a1\u5668S\u6b63\u786e\u4ea4\u6362\u4e86\u53cc\u65b9\u7684\u516c\u7f51IP\u548c\u7aef\u53e3\u4fe1\u606f&#xff0c;\u5e76\u4e14\u5ba2\u6237\u7aef\u89e3\u6790\u65e0\u8bef\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\u9632\u706b\u5899\u8bbe\u7f6e\n<ul>\n<li>\u68c0\u67e5\u4e91\u670d\u52a1\u5668\u3001\u5ba2\u6237\u7aef\u4ee5\u53caNAT\u8bbe\u5907\u7684\u9632\u706b\u5899\u662f\u5426\u5141\u8bb8UDP\u6d41\u91cf\u901a\u8fc7&#xff0c;\u7279\u522b\u662f\u76ee\u6807\u7aef\u53e3\u662f\u5426\u5f00\u653e\u3002<\/li>\n<li>\u4e5f\u9700\u8981\u786e\u4fdd\u53cc\u65b9\u7684UDP\u6253\u6d1e\u7a0b\u5e8f\u6240\u5728\u4e3b\u673a\u5141\u8bb8\u63a5\u6536\u6765\u81ea\u5bf9\u7aef\u7684UDP\u6570\u636e\u5305\u3002<\/li>\n<\/ul>\n<\/li>\n<li>NAT\u6620\u5c04\u95ee\u9898\n<ul>\n<li>\u53ef\u80fd\u4e24\u7aef\u7684NAT\u8bbe\u5907\u7c7b\u578b\u4e0d\u652f\u6301\u76f4\u63a5UDP\u6253\u6d1e&#xff0c;\u6216\u6620\u5c04\u7b56\u7565\u6bd4\u8f83\u4e25\u683c&#xff08;\u4f8b\u5982\u5bf9\u79f0NAT&#xff09;\u3002<\/li>\n<li>\u60a8\u53ef\u4ee5\u68c0\u67e5\u5ba2\u6237\u7aef\u6240\u5728\u7f51\u7edc\u7684NAT\u7c7b\u578b&#xff0c;\u5c1d\u8bd5\u5728\u4e0d\u540c\u7f51\u7edc\u73af\u5883\u4e0b\u6d4b\u8bd5\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\u7aef\u53e3\u7ed1\u5b9a\u548c\u6620\u5c04\u95ee\u9898\n<ul>\n<li>\u786e\u8ba4\u4ee3\u7801\u4e2d\u7ed1\u5b9a\u7684\u672c\u5730\u7aef\u53e3&#xff08;6003\u30016002&#xff09;\u4e0eNAT\u6620\u5c04\u7ed3\u679c\u662f\u5426\u7b26\u5408\u9884\u671f\u3002<\/li>\n<li>\u6709\u4e9bNAT\u8bbe\u5907\u53ef\u80fd\u4f1a\u590d\u7528\u7aef\u53e3\u6216\u8c03\u6574\u5916\u90e8\u6620\u5c04&#xff0c;\u5bfc\u81f4\u53cc\u65b9\u770b\u5230\u76f8\u540c\u7684\u516c\u7f51\u7aef\u53e3&#xff0c;\u4ece\u800c\u5f71\u54cd\u6253\u6d1e\u6548\u679c\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\u4ee3\u7801\u903b\u8f91\u95ee\u9898\n<ul>\n<li>\u60a8\u7684\u4ee3\u7801\u4e2d\u76ee\u524d\u53ea\u662f\u4e0d\u65ad\u53d1\u9001\u6570\u636e\u5305&#xff0c;\u4f46\u5e76\u672a\u5b9e\u73b0\u5bf9\u6536\u5230\u6570\u636e\u5305\u8fdb\u884c\u6709\u6548\u5904\u7406\u3002\u5982\u679c\u5bf9\u7aef\u4e5f\u6ca1\u6709\u6536\u5230\u6570\u636e\u5305&#xff0c;\u53ef\u80fd\u662f\u7531\u4e8e\u53d1\u9001\u65b9\u5411NAT\u8bbe\u5907\u53d1\u9001\u7684\u6570\u636e\u5305\u6ca1\u6709\u6210\u529f\u6620\u5c04\u5230\u5bf9\u7aef\u3002<\/li>\n<\/ul>\n<\/li>\n<h4>1 \u670d\u52a1\u5668\u662f\u5426\u6b63\u786e\u4ea4\u6362\u4e86\u53cc\u65b9\u7684ip\u548c\u7aef\u53e3<\/h4>\n<p>\u8fd9\u4e2a\u6d4b\u8bd5\u7ed3\u679c\u662f\u6211\u7b2c\u56db\u7248\u7684\u7ed3\u679c\u5728\u91cc\u9762\u5df2\u7ecf\u6253\u5370\u51fa\u6765\u5bf9\u5e94\u7684ip&#xff0c;\u7aef\u53e3\u6211\u8fd9\u8fb9\u5bf9\u6bd4\u4e86\u5e76\u672a\u51fa\u73b0\u95ee\u9898 \u4f60\u4eec\u53ef\u4ee5\u518d\u770b\u770b\u4e0a\u9762\u7684\u56fe\u7247 \u7ed3\u8bba:\u6b63\u5e38<\/p>\n<h4>2\u9632\u706b\u5899\u8bbe\u7f6e<\/h4>\n<p>\u672c\u5730\u9632\u706b\u5899&#xff1a; \u68c0\u67e5\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u4e0a\u7684\u9632\u706b\u5899\u72b6\u6001&#xff08;\u4f7f\u7528 ufw status\u3001iptables -L \u7b49\u547d\u4ee4&#xff09;&#xff0c;\u786e\u8ba4UDP\u76ee\u6807\u7aef\u53e3\u662f\u5426\u88ab\u5141\u8bb8\u3002 \u4e91\u9632\u706b\u5899&#xff1a; \u767b\u5f55\u4e91\u670d\u52a1\u5668\u63a7\u5236\u53f0\u6216\u8def\u7531\u5668\u7ba1\u7406\u754c\u9762&#xff0c;\u68c0\u67e5\u662f\u5426\u8bbe\u7f6e\u4e86\u5b89\u5168\u7ec4\u6216\u9632\u706b\u5899\u89c4\u5219&#xff0c;\u786e\u4fdd\u5141\u8bb8\u76f8\u5e94\u7684UDP\u6d41\u91cf&#xff08;\u5305\u62ec\u6ce8\u518c\u7aef\u53e3\u548c\u901a\u4fe1\u7aef\u53e3&#xff09;\u3002<\/p>\n<h5>2.1 \u672c\u5730\u9632\u706b\u5899<\/h5>\n<p>\u672c\u5730\u9632\u706b\u5899\u672a\u6253\u5f00 <img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042106-680476328b21e.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/><\/p>\n<h5>2.2 \u4e91\u670d\u52a1\u5668<\/h5>\n<p>\u9632\u706b\u5899\u5bf9\u5e94\u7aef\u53e3\u5df2\u5f00\u542f <img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042106-68047632ad975.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/> \u7ed3\u8bba:\u6b63\u5e38<\/p>\n<h4>3 \u6293\u5305\u67e5\u770b\u6570\u636e\u5305\u662f\u5426\u53d1\u9001\u51fa\u53bb<\/h4>\n<p>\u5728Ubuntu\u4e0b&#xff0c;\u4f7f\u7528\u6293\u5305\u5de5\u5177\u6765\u76d1\u63a7\u548c\u5206\u6790\u7f51\u7edc\u6570\u636e\u5305\u7684\u6d41\u5411&#xff0c;\u5e38\u7528\u7684\u5de5\u5177\u5305\u62ec tcpdump&#xff08;\u547d\u4ee4\u884c&#xff09;\u548c Wireshark&#xff08;\u56fe\u5f62\u754c\u9762&#xff09;\u3002<\/p>\n<hr \/>\n<h5>3.1. \u4f7f\u7528 tcpdump<\/h5>\n<p>\u5b89\u88c5&#xff1a;<\/p>\n<p><span class=\"token function\">sudo<\/span> <span class=\"token function\">apt-get<\/span> update<br \/>\n<span class=\"token function\">sudo<\/span> <span class=\"token function\">apt-get<\/span> <span class=\"token function\">install<\/span> tcpdump<\/p>\n<p>\u57fa\u672c\u7528\u6cd5&#xff1a;<\/p>\n<ul>\n<li>\n<p>\u6293\u53d6\u6240\u6709\u6570\u636e\u5305&#xff1a;<\/p>\n<p> <span class=\"token function\">sudo<\/span> tcpdump <span class=\"token parameter variable\">-i<\/span> eth0<\/p>\n<p>\u5176\u4e2d eth0 \u662f\u60a8\u8981\u76d1\u63a7\u7684\u7f51\u7edc\u63a5\u53e3&#xff0c;\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 ifconfig \u67e5\u770b\u63a5\u53e3\u540d\u79f0\u3002 \u6211\u7684\u5c31\u662fens33 <img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042106-68047632ee609.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/><\/p>\n<\/li>\n<li>\n<p>\u8fc7\u6ee4\u7279\u5b9a\u534f\u8bae\u548c\u7aef\u53e3&#xff1a;<\/p>\n<p>\u4f8b\u5982&#xff0c;\u6293\u53d6UDP\u6570\u636e\u5305&#xff1a;<\/p>\n<p> <span class=\"token function\">sudo<\/span> tcpdump <span class=\"token parameter variable\">-i<\/span> ens33 udp<\/p>\n<p>\u6293\u53d6\u76ee\u7684\u7aef\u53e3\u4e3a5050\u7684UDP\u6570\u636e\u5305&#xff1a;<\/p>\n<p> <span class=\"token function\">sudo<\/span> tcpdump <span class=\"token parameter variable\">-i<\/span> ens33 udp port <span class=\"token number\">5050<\/span><\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042107-6804763320cd1.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/><img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042107-6804763345f4c.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/> \u6293\u5305\u53d1\u73b0\u6570\u636e\u53d1\u9001\u51fa\u53bb\u4e86<\/p>\n<\/li>\n<\/ul>\n<h4>3 NAT\u6620\u5c04\u95ee\u9898<\/h4>\n<h5>\u4f7f\u7528 stun \u5de5\u5177<\/h5>\n<p>1. \u5b89\u88c5 stun \u5ba2\u6237\u7aef&#xff1a; \u5728 Ubuntu\u7cfb\u7edf\u4e0a\u8fd0\u884c&#xff1a;<\/p>\n<p><span class=\"token function\">sudo<\/span> <span class=\"token function\">apt<\/span> update<br \/>\n<span class=\"token function\">sudo<\/span> <span class=\"token function\">apt<\/span> <span class=\"token function\">install<\/span> stun-client <span class=\"token parameter variable\">-y<\/span><\/p>\n<p>2. \u8fd0\u884c STUN \u5ba2\u6237\u7aef\u6d4b\u8bd5 NAT \u7c7b\u578b<\/p>\n<p>stun stun.l.google.com<\/p>\n<p>\u6216\u8005&#xff1a;<\/p>\n<p>stun stun.sipgate.net<\/p>\n<p>\u8fd9\u662f\u6211\u7684\u7ed3\u679c <img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042107-680476336e111.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/><\/p>\n<ul>\n<li>\n<p>Independent Mapping&#xff08;\u72ec\u7acb\u6620\u5c04&#xff09;&#xff1a; \u6bcf\u4e2a\u5185\u90e8\u7aef\u53e3\u7684\u6620\u5c04\u662f\u72ec\u7acb\u7684&#xff0c;\u5373\u65e0\u8bba\u76ee\u6807\u5730\u5740\u5982\u4f55\u53d8\u5316&#xff0c;\u90fd\u4fdd\u6301\u76f8\u540c\u7684\u6620\u5c04\u3002\u5bf9 UDP \u6253\u6d1e\u6765\u8bf4&#xff0c;\u8fd9\u901a\u5e38\u662f\u6709\u5229\u7684\u3002<\/p>\n<\/li>\n<li>\n<p>Independent Filter&#xff08;\u72ec\u7acb\u8fc7\u6ee4&#xff09;&#xff1a; \u5916\u90e8\u6570\u636e\u5305\u53ea\u8981\u7b26\u5408\u6620\u5c04\u7684\u7aef\u53e3&#xff0c;\u5c31\u4f1a\u88ab\u653e\u884c&#xff0c;\u4e0e\u53d1\u9001\u76ee\u6807\u65e0\u5173\u3002\u8fd9\u610f\u5473\u7740\u53ea\u8981\u5185\u7f51\u8bbe\u5907\u5148\u53d1\u8d77\u901a\u4fe1&#xff0c;\u5916\u90e8\u7684\u56de\u590d\u901a\u5e38\u80fd\u901a\u8fc7 NAT \u8bbe\u5907\u5230\u8fbe\u5185\u7f51\u3002<\/p>\n<\/li>\n<li>\n<p>Random Port&#xff08;\u968f\u673a\u7aef\u53e3&#xff09;&#xff1a; \u6bcf\u4e2a\u65b0\u8fde\u63a5\u53ef\u80fd\u4f1a\u88ab NAT \u5206\u914d\u4e00\u4e2a\u968f\u673a\u7684\u5916\u90e8\u7aef\u53e3&#xff0c;\u8fd9\u53ef\u80fd\u4f1a\u5bfc\u81f4\u7aef\u53e3\u6620\u5c04\u4e0d\u56fa\u5b9a\u3002\u4e3a\u4e86\u4fdd\u6301\u8fde\u63a5&#xff0c;\u5ba2\u6237\u7aef\u9700\u8981\u6301\u7eed\u53d1\u9001\u6570\u636e\u5305\u4ee5\u7ef4\u6301\u6620\u5c04\u3002<\/p>\n<\/li>\n<li>\n<p>No Hairpin&#xff1a; \u8868\u793a NAT \u4e0d\u652f\u6301\u5185\u90e8\u8bbe\u5907\u901a\u8fc7\u516c\u7f51\u5730\u5740\u76f4\u63a5\u8bbf\u95ee\u540c\u4e00 NAT \u5185\u7684\u5176\u4ed6\u8bbe\u5907&#xff08;NAT \u56de\u73af&#xff09;\u3002\u8fd9\u901a\u5e38\u5bf9 UDP \u6253\u6d1e\u5f71\u54cd\u4e0d\u5927&#xff0c;\u56e0\u4e3a C1 \u548c C2 \u662f\u5904\u4e8e\u4e0d\u540c NAT \u6216\u5728\u4e0d\u540c\u7f51\u7edc\u4e0b\u3002<\/p>\n<\/li>\n<li>\n<p>Return value is 0x000012&#xff1a; \u8868\u793a STUN \u5ba2\u6237\u7aef\u68c0\u6d4b\u6210\u529f&#xff0c;\u4f46\u6ca1\u6709\u663e\u793a\u6620\u5c04\u7684\u7aef\u53e3\u8be6\u7ec6\u4fe1\u606f&#xff0c;\u901a\u5e38\u8fd9\u610f\u5473\u7740\u7aef\u53e3\u7531 NAT \u8bbe\u5907\u968f\u673a\u5206\u914d\u3002<\/p>\n<\/li>\n<\/ul>\n<p>\u8fd9\u4e2a\u7ed3\u679c\u8bf4\u660e NAT \u73af\u5883\u662f\u76f8\u5bf9\u6709\u5229\u4e8e UDP \u6253\u6d1e\u7684&#xff08;\u975e\u5bf9\u79f0 NAT&#xff09;&#xff0c;\u4f46\u7531\u4e8e\u968f\u673a\u7aef\u53e3\u7684\u7279\u6027&#xff0c;\u5ba2\u6237\u7aef\u5fc5\u987b\u6301\u7eed\u53d1\u9001\u4fdd\u6301 UDP \u6620\u5c04&#xff08;Keep-Alive&#xff09;\u3002<\/p>\n<p>3. NAT \u7c7b\u578b<\/p>\n<ul>\n<li>Full Cone NAT&#xff08;\u5168\u9525\u5f62 NAT&#xff09; \u2705 UDP \u6253\u6d1e\u6700\u5bb9\u6613\u6210\u529f<\/li>\n<li>Restricted Cone NAT&#xff08;\u53d7\u9650\u9525\u5f62 NAT&#xff09; \u2705 \u9700\u8981\u53cc\u5411\u6570\u636e\u5305\u6253\u6d1e<\/li>\n<li>Port-Restricted Cone NAT&#xff08;\u7aef\u53e3\u53d7\u9650\u9525\u5f62 NAT&#xff09; \u26a0 \u53ef\u80fd\u65e0\u6cd5\u76f4\u63a5\u6253\u6d1e<\/li>\n<li>Symmetric NAT&#xff08;\u5bf9\u79f0 NAT&#xff09; \u274c UDP \u6253\u6d1e\u51e0\u4e4e\u4e0d\u53ef\u80fd\u6210\u529f<\/li>\n<\/ul>\n<p>\u8bc1\u660eNAT\u6620\u5c04\u652f\u6301\u6253\u6d1e<\/p>\n<p>\u6700\u540e\u6000\u7591\u95ee\u9898\u51fa\u5728\u4ee3\u7801\u903b\u8f91\u4e0a&#xff0c;\u670d\u52a1\u5668\u8fd4\u56de\u7684\u7aef\u53e3\u867d\u7136\u6b63\u786e&#xff0c;\u4f46 NAT\u8bbe\u5907 \u5728\u4e00\u6bb5\u65f6\u95f4\u540e\u4fee\u6539\u4e86\u7aef\u53e3\u6620\u5c04&#xff0c;\u6216\u8005\u7aef\u53e3\u6620\u5c04\u88ab\u4e22\u5f03&#xff0c;\u5bfc\u81f4 C1 \u53d1\u9001\u5230\u9519\u8bef\u7aef\u53e3\u3002\u56e0\u6b64\u540e\u7eed\u9700\u8981\u4fee\u6539\u7aef\u53e3\u3002<\/p>\n<p>server.c<\/p>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;sys\/socket.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;arpa\/inet.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;stdio.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;stdlib.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;string.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;unistd.h&gt;<\/span><\/span><\/p>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">define<\/span> <span class=\"token macro-name\">DEFAULT_PORT<\/span> <span class=\"token expression\"><span class=\"token number\">5050<\/span><\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">define<\/span> <span class=\"token macro-name\">BUFFER_SIZE<\/span> <span class=\"token expression\"><span class=\"token number\">100<\/span><\/span><\/span><\/p>\n<p><span class=\"token keyword\">int<\/span> <span class=\"token function\">main<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ server\u5373\u5916\u7f51\u670d\u52a1\u5668<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> serverPort <span class=\"token operator\">&#061;<\/span> DEFAULT_PORT<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> serverListen<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> serverAddr<span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u5efa\u7acb\u76d1\u542csocket<\/span><br \/>\n    serverListen <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">socket<\/span><span class=\"token punctuation\">(<\/span>AF_INET<span class=\"token punctuation\">,<\/span> SOCK_DGRAM<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>serverListen <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;socket() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    serverAddr<span class=\"token punctuation\">.<\/span>sin_family <span class=\"token operator\">&#061;<\/span> AF_INET<span class=\"token punctuation\">;<\/span><br \/>\n    serverAddr<span class=\"token punctuation\">.<\/span>sin_port <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">htons<\/span><span class=\"token punctuation\">(<\/span>serverPort<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    serverAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">.<\/span>s_addr <span class=\"token operator\">&#061;<\/span> INADDR_ANY<span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token function\">bind<\/span><span class=\"token punctuation\">(<\/span>serverListen<span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>serverAddr<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>serverAddr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;bind() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u63a5\u6536\u6765\u81ea\u5ba2\u6237\u7aef\u7684\u8fde\u63a5&#xff0c;source1\u5373\u5148\u8fde\u63a5\u5230S\u7684\u5ba2\u6237\u7aefC1<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> sourceAddr1<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token class-name\">socklen_t<\/span> sourceAddrLen1 <span class=\"token operator\">&#061;<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>sourceAddr1<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> bufRecv1<span class=\"token punctuation\">[<\/span>BUFFER_SIZE<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> len<span class=\"token punctuation\">;<\/span><\/p>\n<p>    len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recvfrom<\/span><span class=\"token punctuation\">(<\/span>serverListen<span class=\"token punctuation\">,<\/span> bufRecv1<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufRecv1<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>sourceAddr1<span class=\"token punctuation\">,<\/span> <span class=\"token operator\">&amp;<\/span>sourceAddrLen1<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;recvfrom() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    bufRecv1<span class=\"token punctuation\">[<\/span>len<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;C1 IP:[%s],PORT:[%d]\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">inet_ntoa<\/span><span class=\"token punctuation\">(<\/span>sourceAddr1<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">ntohs<\/span><span class=\"token punctuation\">(<\/span>sourceAddr1<span class=\"token punctuation\">.<\/span>sin_port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u63a5\u6536\u6765\u81ea\u5ba2\u6237\u7aef\u7684\u8fde\u63a5&#xff0c;source2\u5373\u540e\u8fde\u63a5\u5230S\u7684\u5ba2\u6237\u7aefC2<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> sourceAddr2<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token class-name\">socklen_t<\/span> sourceAddrLen2 <span class=\"token operator\">&#061;<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>sourceAddr2<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> bufRecv2<span class=\"token punctuation\">[<\/span>BUFFER_SIZE<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recvfrom<\/span><span class=\"token punctuation\">(<\/span>serverListen<span class=\"token punctuation\">,<\/span> bufRecv2<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufRecv2<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>sourceAddr2<span class=\"token punctuation\">,<\/span> <span class=\"token operator\">&amp;<\/span>sourceAddrLen2<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;recvfrom() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    bufRecv2<span class=\"token punctuation\">[<\/span>len<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;C2 IP:[%s],PORT:[%d]\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">inet_ntoa<\/span><span class=\"token punctuation\">(<\/span>sourceAddr2<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">ntohs<\/span><span class=\"token punctuation\">(<\/span>sourceAddr2<span class=\"token punctuation\">.<\/span>sin_port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u5411C1\u53d1\u9001C2\u7684\u5916\u7f51ip\u548cport<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> bufSend1<span class=\"token punctuation\">[<\/span>BUFFER_SIZE<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><span class=\"token comment\">\/\/ bufSend1\u4e2d\u5b58\u50a8C2\u7684\u5916\u7f51ip\u548cport<\/span><br \/>\n    <span class=\"token function\">memset<\/span><span class=\"token punctuation\">(<\/span>bufSend1<span class=\"token punctuation\">,<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufSend1<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> <span class=\"token operator\">*<\/span>ip2 <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">inet_ntoa<\/span><span class=\"token punctuation\">(<\/span>sourceAddr2<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><span class=\"token comment\">\/\/ C2\u7684ip<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> port2<span class=\"token punctuation\">[<\/span><span class=\"token number\">10<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><span class=\"token comment\">\/\/ C2\u7684port<\/span><br \/>\n    <span class=\"token function\">snprintf<\/span><span class=\"token punctuation\">(<\/span>port2<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>port2<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;%d&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">ntohs<\/span><span class=\"token punctuation\">(<\/span>sourceAddr2<span class=\"token punctuation\">.<\/span>sin_port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">snprintf<\/span><span class=\"token punctuation\">(<\/span>bufSend1<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufSend1<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;%s^%s&#034;<\/span><span class=\"token punctuation\">,<\/span> ip2<span class=\"token punctuation\">,<\/span> port2<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">sendto<\/span><span class=\"token punctuation\">(<\/span>serverListen<span class=\"token punctuation\">,<\/span> bufSend1<span class=\"token punctuation\">,<\/span> <span class=\"token function\">strlen<\/span><span class=\"token punctuation\">(<\/span>bufSend1<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>sourceAddr1<span class=\"token punctuation\">,<\/span> sourceAddrLen1<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;sendto() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;send() byte:%d\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> len<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u5411C2\u53d1\u9001C1\u7684\u5916\u7f51ip\u548cport<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> bufSend2<span class=\"token punctuation\">[<\/span>BUFFER_SIZE<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><span class=\"token comment\">\/\/ bufSend2\u4e2d\u5b58\u50a8C1\u7684\u5916\u7f51ip\u548cport<\/span><br \/>\n    <span class=\"token function\">memset<\/span><span class=\"token punctuation\">(<\/span>bufSend2<span class=\"token punctuation\">,<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufSend2<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> <span class=\"token operator\">*<\/span>ip1 <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">inet_ntoa<\/span><span class=\"token punctuation\">(<\/span>sourceAddr1<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><span class=\"token comment\">\/\/ C1\u7684ip<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> port1<span class=\"token punctuation\">[<\/span><span class=\"token number\">10<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><span class=\"token comment\">\/\/ C1\u7684port<\/span><br \/>\n    <span class=\"token function\">snprintf<\/span><span class=\"token punctuation\">(<\/span>port1<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>port1<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;%d&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">ntohs<\/span><span class=\"token punctuation\">(<\/span>sourceAddr1<span class=\"token punctuation\">.<\/span>sin_port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">snprintf<\/span><span class=\"token punctuation\">(<\/span>bufSend2<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufSend2<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;%s^%s&#034;<\/span><span class=\"token punctuation\">,<\/span> ip1<span class=\"token punctuation\">,<\/span> port1<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">sendto<\/span><span class=\"token punctuation\">(<\/span>serverListen<span class=\"token punctuation\">,<\/span> bufSend2<span class=\"token punctuation\">,<\/span> <span class=\"token function\">strlen<\/span><span class=\"token punctuation\">(<\/span>bufSend2<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>sourceAddr2<span class=\"token punctuation\">,<\/span> sourceAddrLen2<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;sendto() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;send() byte:%d\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> len<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ server\u7684\u4e2d\u95f4\u4eba\u5de5\u4f5c\u5df2\u5b8c\u6210&#xff0c;\u9000\u51fa\u5373\u53ef&#xff0c;\u5269\u4e0b\u7684\u4ea4\u7ed9C1\u4e0eC2\u76f8\u4e92\u901a\u4fe1<\/span><br \/>\n    <span class=\"token function\">close<\/span><span class=\"token punctuation\">(<\/span>serverListen<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">return<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p>client1.c<\/p>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;sys\/socket.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;arpa\/inet.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;stdio.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;stdlib.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;string.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;unistd.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;fcntl.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;errno.h&gt;<\/span><\/span><\/p>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">define<\/span> <span class=\"token macro-name\">PORT<\/span> <span class=\"token expression\"><span class=\"token number\">6003<\/span><\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">define<\/span> <span class=\"token macro-name\">BUFFER_SIZE<\/span> <span class=\"token expression\"><span class=\"token number\">100<\/span><\/span><\/span><\/p>\n<p><span class=\"token keyword\">int<\/span> <span class=\"token function\">main<\/span><span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span> argc<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">char<\/span><span class=\"token operator\">*<\/span> argv<span class=\"token punctuation\">[<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> serverAddr<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> thisAddr<span class=\"token punctuation\">;<\/span><\/p>\n<p>    thisAddr<span class=\"token punctuation\">.<\/span>sin_family <span class=\"token operator\">&#061;<\/span> AF_INET<span class=\"token punctuation\">;<\/span><br \/>\n    thisAddr<span class=\"token punctuation\">.<\/span>sin_port <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">htons<\/span><span class=\"token punctuation\">(<\/span>PORT<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    thisAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">.<\/span>s_addr <span class=\"token operator\">&#061;<\/span> INADDR_ANY<span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>argc <span class=\"token operator\">&lt;<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;Usage: UDPClient1 &lt;Server IP address&gt; &lt;Server Port&gt;\\\\n&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> sockS <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">socket<\/span><span class=\"token punctuation\">(<\/span>AF_INET<span class=\"token punctuation\">,<\/span> SOCK_DGRAM<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>sockS <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;socket() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token function\">bind<\/span><span class=\"token punctuation\">(<\/span>sockS<span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>thisAddr<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>thisAddr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;bind() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> sockC <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">socket<\/span><span class=\"token punctuation\">(<\/span>AF_INET<span class=\"token punctuation\">,<\/span> SOCK_DGRAM<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>sockC <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;socket() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u5141\u8bb8\u7aef\u53e3\u590d\u7528<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> optval <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">setsockopt<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> SOL_SOCKET<span class=\"token punctuation\">,<\/span> SO_REUSEADDR<span class=\"token punctuation\">,<\/span> <span class=\"token operator\">&amp;<\/span>optval<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>optval<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u7ed1\u5b9a\u56fa\u5b9a\u7aef\u53e3 6003<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> bindAddr<span class=\"token punctuation\">;<\/span><br \/>\n    bindAddr<span class=\"token punctuation\">.<\/span>sin_family <span class=\"token operator\">&#061;<\/span> AF_INET<span class=\"token punctuation\">;<\/span><br \/>\n    bindAddr<span class=\"token punctuation\">.<\/span>sin_port <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">htons<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">6003<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    bindAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">.<\/span>s_addr <span class=\"token operator\">&#061;<\/span> INADDR_ANY<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">bind<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>bindAddr<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bindAddr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">char<\/span> bufSend<span class=\"token punctuation\">[<\/span><span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token string\">&#034;I am C1&#034;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> bufRecv<span class=\"token punctuation\">[<\/span>BUFFER_SIZE<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">memset<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">,<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> sourceAddr<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token class-name\">socklen_t<\/span> sourceAddrLen <span class=\"token operator\">&#061;<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>sourceAddr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> oppositeSideAddr<span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> len<span class=\"token punctuation\">;<\/span><\/p>\n<p>    serverAddr<span class=\"token punctuation\">.<\/span>sin_family <span class=\"token operator\">&#061;<\/span> AF_INET<span class=\"token punctuation\">;<\/span><br \/>\n    serverAddr<span class=\"token punctuation\">.<\/span>sin_port <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">htons<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">atoi<\/span><span class=\"token punctuation\">(<\/span>argv<span class=\"token punctuation\">[<\/span><span class=\"token number\">2<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    serverAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">.<\/span>s_addr <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">inet_addr<\/span><span class=\"token punctuation\">(<\/span>argv<span class=\"token punctuation\">[<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">sendto<\/span><span class=\"token punctuation\">(<\/span>sockS<span class=\"token punctuation\">,<\/span> bufSend<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufSend<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>serverAddr<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>serverAddr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;sendto() to S failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;C1 sent registration packet to server S.\\\\n&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recvfrom<\/span><span class=\"token punctuation\">(<\/span>sockS<span class=\"token punctuation\">,<\/span> bufRecv<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>sourceAddr<span class=\"token punctuation\">,<\/span> <span class=\"token operator\">&amp;<\/span>sourceAddrLen<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;recvfrom() from S failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    bufRecv<span class=\"token punctuation\">[<\/span>len<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;C1 received from S: %s\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token function\">close<\/span><span class=\"token punctuation\">(<\/span>sockS<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">char<\/span> ip<span class=\"token punctuation\">[<\/span><span class=\"token number\">20<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> port<span class=\"token punctuation\">[<\/span><span class=\"token number\">10<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> i <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span>i <span class=\"token operator\">&lt;<\/span> <span class=\"token function\">strlen<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&amp;&amp;<\/span> bufRecv<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">!&#061;<\/span> <span class=\"token char\">&#039;^&#039;<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        ip<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> bufRecv<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        i<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    ip<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> j <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    i<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span>i <span class=\"token operator\">&lt;<\/span> <span class=\"token function\">strlen<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        port<span class=\"token punctuation\">[<\/span>j<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> bufRecv<span class=\"token punctuation\">[<\/span>i<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    port<span class=\"token punctuation\">[<\/span>j<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    oppositeSideAddr<span class=\"token punctuation\">.<\/span>sin_family <span class=\"token operator\">&#061;<\/span> AF_INET<span class=\"token punctuation\">;<\/span><br \/>\n    oppositeSideAddr<span class=\"token punctuation\">.<\/span>sin_port <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">htons<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">atoi<\/span><span class=\"token punctuation\">(<\/span>port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    oppositeSideAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">.<\/span>s_addr <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">inet_addr<\/span><span class=\"token punctuation\">(<\/span>ip<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> flags <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">fcntl<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> F_GETFL<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">fcntl<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> F_SETFL<span class=\"token punctuation\">,<\/span> flags <span class=\"token operator\">|<\/span> O_NONBLOCK<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;C1 will now try to communicate directly with C2 at %s:%s\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> ip<span class=\"token punctuation\">,<\/span> port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> attempts <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">usleep<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">500000<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>  <span class=\"token comment\">\/\/ 500ms \u53d1\u9001\u4e00\u6b21<\/span><\/p>\n<p>        len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">sendto<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> bufSend<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufSend<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>oppositeSideAddr<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>oppositeSideAddr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;sendto() to C2 failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;Sent keep-alive UDP packet to %s:%d\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">inet_ntoa<\/span><span class=\"token punctuation\">(<\/span>oppositeSideAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">ntohs<\/span><span class=\"token punctuation\">(<\/span>oppositeSideAddr<span class=\"token punctuation\">.<\/span>sin_port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span><\/p>\n<p>        len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recvfrom<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> bufRecv<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>sourceAddr<span class=\"token punctuation\">,<\/span> <span class=\"token operator\">&amp;<\/span>sourceAddrLen<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>errno <span class=\"token operator\">&#061;&#061;<\/span> EAGAIN <span class=\"token operator\">||<\/span> errno <span class=\"token operator\">&#061;&#061;<\/span> EWOULDBLOCK<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                attempts<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>attempts <span class=\"token operator\">%<\/span> <span class=\"token number\">10<\/span> <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                    <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;No response from C2 after 5 seconds. Retrying&#8230;\\\\n&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                <span class=\"token punctuation\">}<\/span><br \/>\n                <span class=\"token keyword\">continue<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;recvfrom() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                <span class=\"token keyword\">break<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token punctuation\">}<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            bufRecv<span class=\"token punctuation\">[<\/span>len<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;C1 received from C2 [%s:%d]: %s\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">inet_ntoa<\/span><span class=\"token punctuation\">(<\/span>sourceAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">ntohs<\/span><span class=\"token punctuation\">(<\/span>sourceAddr<span class=\"token punctuation\">.<\/span>sin_port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            attempts <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span>  <span class=\"token comment\">\/\/ \u6210\u529f\u6536\u5230\u6570\u636e&#xff0c;\u91cd\u7f6e\u91cd\u8bd5\u8ba1\u6570<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token function\">close<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">return<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p>client2.c<\/p>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;sys\/socket.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;arpa\/inet.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;stdio.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;stdlib.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;string.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;unistd.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;fcntl.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;errno.h&gt;<\/span><\/span><\/p>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">define<\/span> <span class=\"token macro-name\">PORT<\/span> <span class=\"token expression\"><span class=\"token number\">6002<\/span><\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">define<\/span> <span class=\"token macro-name\">BUFFER_SIZE<\/span> <span class=\"token expression\"><span class=\"token number\">100<\/span><\/span><\/span><\/p>\n<p><span class=\"token keyword\">int<\/span> <span class=\"token function\">main<\/span><span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span> argc<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">char<\/span><span class=\"token operator\">*<\/span> argv<span class=\"token punctuation\">[<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> serverAddr<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> thisAddr<span class=\"token punctuation\">;<\/span><\/p>\n<p>    thisAddr<span class=\"token punctuation\">.<\/span>sin_family <span class=\"token operator\">&#061;<\/span> AF_INET<span class=\"token punctuation\">;<\/span><br \/>\n    thisAddr<span class=\"token punctuation\">.<\/span>sin_port <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">htons<\/span><span class=\"token punctuation\">(<\/span>PORT<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    thisAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">.<\/span>s_addr <span class=\"token operator\">&#061;<\/span> INADDR_ANY<span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>argc <span class=\"token operator\">&lt;<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;Usage: UDPClient2 &lt;Server IP address&gt; &lt;Server Port&gt;\\\\n&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> sockS <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">socket<\/span><span class=\"token punctuation\">(<\/span>AF_INET<span class=\"token punctuation\">,<\/span> SOCK_DGRAM<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>sockS <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;socket() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token function\">bind<\/span><span class=\"token punctuation\">(<\/span>sockS<span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>thisAddr<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>thisAddr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;bind() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> sockC <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">socket<\/span><span class=\"token punctuation\">(<\/span>AF_INET<span class=\"token punctuation\">,<\/span> SOCK_DGRAM<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>sockC <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;socket() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u5141\u8bb8\u7aef\u53e3\u590d\u7528<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> optval <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">setsockopt<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> SOL_SOCKET<span class=\"token punctuation\">,<\/span> SO_REUSEADDR<span class=\"token punctuation\">,<\/span> <span class=\"token operator\">&amp;<\/span>optval<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>optval<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u7ed1\u5b9a\u56fa\u5b9a\u7aef\u53e3 6002<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> bindAddr<span class=\"token punctuation\">;<\/span><br \/>\n    bindAddr<span class=\"token punctuation\">.<\/span>sin_family <span class=\"token operator\">&#061;<\/span> AF_INET<span class=\"token punctuation\">;<\/span><br \/>\n    bindAddr<span class=\"token punctuation\">.<\/span>sin_port <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">htons<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">6002<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    bindAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">.<\/span>s_addr <span class=\"token operator\">&#061;<\/span> INADDR_ANY<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">bind<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>bindAddr<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bindAddr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">char<\/span> bufSend<span class=\"token punctuation\">[<\/span><span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token string\">&#034;I am C2&#034;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> bufRecv<span class=\"token punctuation\">[<\/span>BUFFER_SIZE<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">memset<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">,<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> sourceAddr<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token class-name\">socklen_t<\/span> sourceAddrLen <span class=\"token operator\">&#061;<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>sourceAddr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr_in<\/span> oppositeSideAddr<span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> len<span class=\"token punctuation\">;<\/span><\/p>\n<p>    serverAddr<span class=\"token punctuation\">.<\/span>sin_family <span class=\"token operator\">&#061;<\/span> AF_INET<span class=\"token punctuation\">;<\/span><br \/>\n    serverAddr<span class=\"token punctuation\">.<\/span>sin_port <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">htons<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">atoi<\/span><span class=\"token punctuation\">(<\/span>argv<span class=\"token punctuation\">[<\/span><span class=\"token number\">2<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    serverAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">.<\/span>s_addr <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">inet_addr<\/span><span class=\"token punctuation\">(<\/span>argv<span class=\"token punctuation\">[<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">sendto<\/span><span class=\"token punctuation\">(<\/span>sockS<span class=\"token punctuation\">,<\/span> bufSend<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufSend<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>serverAddr<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>serverAddr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;sendto() to S failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;C2 sent registration packet to server S.\\\\n&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recvfrom<\/span><span class=\"token punctuation\">(<\/span>sockS<span class=\"token punctuation\">,<\/span> bufRecv<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>sourceAddr<span class=\"token punctuation\">,<\/span> <span class=\"token operator\">&amp;<\/span>sourceAddrLen<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;recvfrom() from S failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    bufRecv<span class=\"token punctuation\">[<\/span>len<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;C2 received from S: %s\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token function\">close<\/span><span class=\"token punctuation\">(<\/span>sockS<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">char<\/span> ip<span class=\"token punctuation\">[<\/span><span class=\"token number\">20<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">char<\/span> port<span class=\"token punctuation\">[<\/span><span class=\"token number\">10<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> i <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span>i <span class=\"token operator\">&lt;<\/span> <span class=\"token function\">strlen<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&amp;&amp;<\/span> bufRecv<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">!&#061;<\/span> <span class=\"token char\">&#039;^&#039;<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        ip<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> bufRecv<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        i<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    ip<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> j <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    i<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span>i <span class=\"token operator\">&lt;<\/span> <span class=\"token function\">strlen<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        port<span class=\"token punctuation\">[<\/span>j<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> bufRecv<span class=\"token punctuation\">[<\/span>i<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    port<span class=\"token punctuation\">[<\/span>j<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    oppositeSideAddr<span class=\"token punctuation\">.<\/span>sin_family <span class=\"token operator\">&#061;<\/span> AF_INET<span class=\"token punctuation\">;<\/span><br \/>\n    oppositeSideAddr<span class=\"token punctuation\">.<\/span>sin_port <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">htons<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">atoi<\/span><span class=\"token punctuation\">(<\/span>port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    oppositeSideAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">.<\/span>s_addr <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">inet_addr<\/span><span class=\"token punctuation\">(<\/span>ip<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> flags <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">fcntl<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> F_GETFL<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">fcntl<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> F_SETFL<span class=\"token punctuation\">,<\/span> flags <span class=\"token operator\">|<\/span> O_NONBLOCK<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;C2 will now try to communicate directly with C1 at %s:%s\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> ip<span class=\"token punctuation\">,<\/span> port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> attempts <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">usleep<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">500000<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>  <span class=\"token comment\">\/\/ 500ms \u53d1\u9001\u4e00\u6b21<\/span><\/p>\n<p>        len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">sendto<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> bufSend<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufSend<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>oppositeSideAddr<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>oppositeSideAddr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;sendto() to C1 failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;Sent keep-alive UDP packet to %s:%d\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">inet_ntoa<\/span><span class=\"token punctuation\">(<\/span>oppositeSideAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">ntohs<\/span><span class=\"token punctuation\">(<\/span>oppositeSideAddr<span class=\"token punctuation\">.<\/span>sin_port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span><\/p>\n<p>        len <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recvfrom<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">,<\/span> bufRecv<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">struct<\/span> <span class=\"token class-name\">sockaddr<\/span> <span class=\"token operator\">*<\/span><span class=\"token punctuation\">)<\/span><span class=\"token operator\">&amp;<\/span>sourceAddr<span class=\"token punctuation\">,<\/span> <span class=\"token operator\">&amp;<\/span>sourceAddrLen<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>errno <span class=\"token operator\">&#061;&#061;<\/span> EAGAIN <span class=\"token operator\">||<\/span> errno <span class=\"token operator\">&#061;&#061;<\/span> EWOULDBLOCK<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                attempts<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>attempts <span class=\"token operator\">%<\/span> <span class=\"token number\">10<\/span> <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                    <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;No response from C1 after 5 seconds. Retrying&#8230;\\\\n&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                <span class=\"token punctuation\">}<\/span><br \/>\n                <span class=\"token keyword\">continue<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;recvfrom() failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                <span class=\"token keyword\">break<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token punctuation\">}<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            bufRecv<span class=\"token punctuation\">[<\/span>len<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;C2 received from C1 [%s:%d]: %s\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">inet_ntoa<\/span><span class=\"token punctuation\">(<\/span>sourceAddr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token function\">ntohs<\/span><span class=\"token punctuation\">(<\/span>sourceAddr<span class=\"token punctuation\">.<\/span>sin_port<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> bufRecv<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            attempts <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span>  <span class=\"token comment\">\/\/ \u6210\u529f\u6536\u5230\u6570\u636e&#xff0c;\u91cd\u7f6e\u91cd\u8bd5\u8ba1\u6570<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token function\">close<\/span><span class=\"token punctuation\">(<\/span>sockC<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">return<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb1.1k\u6b21\uff0c\u70b9\u8d5e26\u6b21\uff0c\u6536\u85cf13\u6b21\u3002\u4e0a\u6b21\u8bf4\u57fa\u4e8eUDP\u7684\u6253\u6d1e\u7a0b\u5e8f\u6539\u4e86\u4e94\u7248\u4e00\u76f4\u6ca1\u6709\u6210\u529f\uff0c\u8981\u5199\u4e00\u4e0b\u95ee\u9898\u6240\u5728\uff0c\u4f46\u662f\u6211\u540e\u7eed\u53c8\u67e5\u8be2\u4e86\u4e00\u4e9b\u8d44\u6599\uff0c\u6210\u529f\u5b9e\u73b0\u4e86\uff0c\u8fd9\u6b21\u5148\u5199\u4e00\u4e0b\uff0c\u6211\u8ba4\u4e3a\u672a\u6210\u529f\u7684\u6392\u67e5\u9519\u8bef\u7684\u90e8\u5206\u4e5f\u5f88\u91cd\u8981\uff0c\u5982\u679c\u60f3\u76f4\u63a5\u770b\u6210\u529f\u7684\u53ef\u4ee5\u76f4\u63a5\u770b\u6211\u7684\u4e0b\u4e00\u7bc7\u6587\u7ae0\u3002\u9996\u5148 \u57fa\u4e8e\u4e0a\u7bc7\u6587\u7ae0\u7684UDP\u6253\u6d1e\u903b\u8f91\u8fd9\u91cc\u76f4\u63a5\u5c06\u56fe\u8d34\u51fa\u6765\uff1a\u6211\u7684\u903b\u8f91\u601d\u8def\uff1a\uff08ps:\u4f1a\u628a\u4ee3\u7801\u8d34\u5230\u6700\u540e\u9762\u3002_autodl stun \u6253\u6d1e\u5931\u8d25<\/p>\n","protected":false},"author":2,"featured_media":29733,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[58,43,78],"topic":[],"class_list":["post-29743","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-server","tag-linux","tag-43","tag-78"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v20.3 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>\u3010Linux\u3011\u3010\u7f51\u7edc\u3011UDP\u6253\u6d1e-\uff1e\u4e0d\u540c\u5b50\u7f51\u4e0b\u7684\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u901a\u4fe1\uff08\u672a\u6210\u529f\u7248\uff09 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.wsisp.com\/helps\/29743.html\" \/>\n<meta property=\"og:locale\" content=\"zh_CN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"\u3010Linux\u3011\u3010\u7f51\u7edc\u3011UDP\u6253\u6d1e-\uff1e\u4e0d\u540c\u5b50\u7f51\u4e0b\u7684\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u901a\u4fe1\uff08\u672a\u6210\u529f\u7248\uff09 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"og:description\" content=\"\u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb1.1k\u6b21\uff0c\u70b9\u8d5e26\u6b21\uff0c\u6536\u85cf13\u6b21\u3002\u4e0a\u6b21\u8bf4\u57fa\u4e8eUDP\u7684\u6253\u6d1e\u7a0b\u5e8f\u6539\u4e86\u4e94\u7248\u4e00\u76f4\u6ca1\u6709\u6210\u529f\uff0c\u8981\u5199\u4e00\u4e0b\u95ee\u9898\u6240\u5728\uff0c\u4f46\u662f\u6211\u540e\u7eed\u53c8\u67e5\u8be2\u4e86\u4e00\u4e9b\u8d44\u6599\uff0c\u6210\u529f\u5b9e\u73b0\u4e86\uff0c\u8fd9\u6b21\u5148\u5199\u4e00\u4e0b\uff0c\u6211\u8ba4\u4e3a\u672a\u6210\u529f\u7684\u6392\u67e5\u9519\u8bef\u7684\u90e8\u5206\u4e5f\u5f88\u91cd\u8981\uff0c\u5982\u679c\u60f3\u76f4\u63a5\u770b\u6210\u529f\u7684\u53ef\u4ee5\u76f4\u63a5\u770b\u6211\u7684\u4e0b\u4e00\u7bc7\u6587\u7ae0\u3002\u9996\u5148 \u57fa\u4e8e\u4e0a\u7bc7\u6587\u7ae0\u7684UDP\u6253\u6d1e\u903b\u8f91\u8fd9\u91cc\u76f4\u63a5\u5c06\u56fe\u8d34\u51fa\u6765\uff1a\u6211\u7684\u903b\u8f91\u601d\u8def\uff1a\uff08ps:\u4f1a\u628a\u4ee3\u7801\u8d34\u5230\u6700\u540e\u9762\u3002_autodl stun \u6253\u6d1e\u5931\u8d25\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.wsisp.com\/helps\/29743.html\" \/>\n<meta property=\"og:site_name\" content=\"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"article:published_time\" content=\"2025-04-20T04:21:08+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042105-6804763187358.png\" \/>\n<meta name=\"author\" content=\"admin\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u4f5c\u8005\" \/>\n\t<meta name=\"twitter:data1\" content=\"admin\" \/>\n\t<meta name=\"twitter:label2\" content=\"\u9884\u8ba1\u9605\u8bfb\u65f6\u95f4\" \/>\n\t<meta name=\"twitter:data2\" content=\"9 \u5206\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/29743.html\",\"url\":\"https:\/\/www.wsisp.com\/helps\/29743.html\",\"name\":\"\u3010Linux\u3011\u3010\u7f51\u7edc\u3011UDP\u6253\u6d1e-\uff1e\u4e0d\u540c\u5b50\u7f51\u4e0b\u7684\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u901a\u4fe1\uff08\u672a\u6210\u529f\u7248\uff09 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\",\"isPartOf\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/#website\"},\"datePublished\":\"2025-04-20T04:21:08+00:00\",\"dateModified\":\"2025-04-20T04:21:08+00:00\",\"author\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41\"},\"breadcrumb\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/29743.html#breadcrumb\"},\"inLanguage\":\"zh-Hans\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.wsisp.com\/helps\/29743.html\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/29743.html#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"\u9996\u9875\",\"item\":\"https:\/\/www.wsisp.com\/helps\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"\u3010Linux\u3011\u3010\u7f51\u7edc\u3011UDP\u6253\u6d1e--\uff1e\u4e0d\u540c\u5b50\u7f51\u4e0b\u7684\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u901a\u4fe1\uff08\u672a\u6210\u529f\u7248\uff09\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/#website\",\"url\":\"https:\/\/www.wsisp.com\/helps\/\",\"name\":\"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\",\"description\":\"\u9999\u6e2f\u670d\u52a1\u5668_\u9999\u6e2f\u4e91\u670d\u52a1\u5668\u8d44\u8baf_\u670d\u52a1\u5668\u5e2e\u52a9\u6587\u6863_\u670d\u52a1\u5668\u6559\u7a0b\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/www.wsisp.com\/helps\/?s={search_term_string}\"},\"query-input\":\"required name=search_term_string\"}],\"inLanguage\":\"zh-Hans\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41\",\"name\":\"admin\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"zh-Hans\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery\",\"contentUrl\":\"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery\",\"caption\":\"admin\"},\"sameAs\":[\"http:\/\/wp.wsisp.com\"],\"url\":\"https:\/\/www.wsisp.com\/helps\/author\/admin\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"\u3010Linux\u3011\u3010\u7f51\u7edc\u3011UDP\u6253\u6d1e-\uff1e\u4e0d\u540c\u5b50\u7f51\u4e0b\u7684\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u901a\u4fe1\uff08\u672a\u6210\u529f\u7248\uff09 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.wsisp.com\/helps\/29743.html","og_locale":"zh_CN","og_type":"article","og_title":"\u3010Linux\u3011\u3010\u7f51\u7edc\u3011UDP\u6253\u6d1e-\uff1e\u4e0d\u540c\u5b50\u7f51\u4e0b\u7684\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u901a\u4fe1\uff08\u672a\u6210\u529f\u7248\uff09 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","og_description":"\u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb1.1k\u6b21\uff0c\u70b9\u8d5e26\u6b21\uff0c\u6536\u85cf13\u6b21\u3002\u4e0a\u6b21\u8bf4\u57fa\u4e8eUDP\u7684\u6253\u6d1e\u7a0b\u5e8f\u6539\u4e86\u4e94\u7248\u4e00\u76f4\u6ca1\u6709\u6210\u529f\uff0c\u8981\u5199\u4e00\u4e0b\u95ee\u9898\u6240\u5728\uff0c\u4f46\u662f\u6211\u540e\u7eed\u53c8\u67e5\u8be2\u4e86\u4e00\u4e9b\u8d44\u6599\uff0c\u6210\u529f\u5b9e\u73b0\u4e86\uff0c\u8fd9\u6b21\u5148\u5199\u4e00\u4e0b\uff0c\u6211\u8ba4\u4e3a\u672a\u6210\u529f\u7684\u6392\u67e5\u9519\u8bef\u7684\u90e8\u5206\u4e5f\u5f88\u91cd\u8981\uff0c\u5982\u679c\u60f3\u76f4\u63a5\u770b\u6210\u529f\u7684\u53ef\u4ee5\u76f4\u63a5\u770b\u6211\u7684\u4e0b\u4e00\u7bc7\u6587\u7ae0\u3002\u9996\u5148 \u57fa\u4e8e\u4e0a\u7bc7\u6587\u7ae0\u7684UDP\u6253\u6d1e\u903b\u8f91\u8fd9\u91cc\u76f4\u63a5\u5c06\u56fe\u8d34\u51fa\u6765\uff1a\u6211\u7684\u903b\u8f91\u601d\u8def\uff1a\uff08ps:\u4f1a\u628a\u4ee3\u7801\u8d34\u5230\u6700\u540e\u9762\u3002_autodl stun \u6253\u6d1e\u5931\u8d25","og_url":"https:\/\/www.wsisp.com\/helps\/29743.html","og_site_name":"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","article_published_time":"2025-04-20T04:21:08+00:00","og_image":[{"url":"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250420042105-6804763187358.png"}],"author":"admin","twitter_card":"summary_large_image","twitter_misc":{"\u4f5c\u8005":"admin","\u9884\u8ba1\u9605\u8bfb\u65f6\u95f4":"9 \u5206"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/www.wsisp.com\/helps\/29743.html","url":"https:\/\/www.wsisp.com\/helps\/29743.html","name":"\u3010Linux\u3011\u3010\u7f51\u7edc\u3011UDP\u6253\u6d1e-\uff1e\u4e0d\u540c\u5b50\u7f51\u4e0b\u7684\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u901a\u4fe1\uff08\u672a\u6210\u529f\u7248\uff09 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","isPartOf":{"@id":"https:\/\/www.wsisp.com\/helps\/#website"},"datePublished":"2025-04-20T04:21:08+00:00","dateModified":"2025-04-20T04:21:08+00:00","author":{"@id":"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41"},"breadcrumb":{"@id":"https:\/\/www.wsisp.com\/helps\/29743.html#breadcrumb"},"inLanguage":"zh-Hans","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.wsisp.com\/helps\/29743.html"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/www.wsisp.com\/helps\/29743.html#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"\u9996\u9875","item":"https:\/\/www.wsisp.com\/helps"},{"@type":"ListItem","position":2,"name":"\u3010Linux\u3011\u3010\u7f51\u7edc\u3011UDP\u6253\u6d1e--\uff1e\u4e0d\u540c\u5b50\u7f51\u4e0b\u7684\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u901a\u4fe1\uff08\u672a\u6210\u529f\u7248\uff09"}]},{"@type":"WebSite","@id":"https:\/\/www.wsisp.com\/helps\/#website","url":"https:\/\/www.wsisp.com\/helps\/","name":"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","description":"\u9999\u6e2f\u670d\u52a1\u5668_\u9999\u6e2f\u4e91\u670d\u52a1\u5668\u8d44\u8baf_\u670d\u52a1\u5668\u5e2e\u52a9\u6587\u6863_\u670d\u52a1\u5668\u6559\u7a0b","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.wsisp.com\/helps\/?s={search_term_string}"},"query-input":"required name=search_term_string"}],"inLanguage":"zh-Hans"},{"@type":"Person","@id":"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41","name":"admin","image":{"@type":"ImageObject","inLanguage":"zh-Hans","@id":"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/image\/","url":"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery","contentUrl":"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery","caption":"admin"},"sameAs":["http:\/\/wp.wsisp.com"],"url":"https:\/\/www.wsisp.com\/helps\/author\/admin"}]}},"_links":{"self":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/posts\/29743","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/comments?post=29743"}],"version-history":[{"count":0,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/posts\/29743\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/media\/29733"}],"wp:attachment":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/media?parent=29743"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/categories?post=29743"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/tags?post=29743"},{"taxonomy":"topic","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/topic?post=29743"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}