\nIO \u591a\u8def\u8f6c\u63a5\u672c\u8d28：<\/p>\n<\/p>\n
- \n
- \u5728\u670d\u52a1\u5668\u7aef\u6709\u4e24\u7c7b\u6587\u4ef6\u63cf\u8ff0\u7b26，\u5206\u522b\u5bf9\u5e94\u4e00\u4e2a\u8bfb\u7f13\u51b2\u533a\u548c\u5199\u7f13\u51b2\u533a<\/li>\n
- \u7528\u4e8e\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u5bf9\u5e94\u7684\u8bfb\u7f13\u51b2\u533a\u4e3b\u8981\u7528\u6765\u5b58\u50a8\u5ba2\u6237\u7aef\u7684\u8fde\u63a5\u8bf7\u6c42，\u5f53\u8c03\u7528 accept \u65f6\u4f1a\u68c0\u6d4b\u8fd9\u4e2a\u8bfb\u7f13\u51b2\u533a\u662f\u5426\u6709\u8fde\u63a5\u8bf7\u6c42<\/li>\n
- \u7528\u4e8e\u901a\u4fe1\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u5bf9\u5e94\u7684\u8bfb\u7f13\u51b2\u533a\u7528\u4e8e\u5b58\u50a8\u5ba2\u6237\u7aef\u53d1\u9001\u6765\u7684\u6570\u636e，\u670d\u52a1\u5668\u8c03\u7528 read \u65b9\u6cd5\u80fd\u591f\u5c06\u6570\u636e\u8bfb\u53d6\u51fa\u6765，\u5199\u7f13\u51b2\u533a\u7528\u4e8e\u670d\u52a1\u5668\u901a\u8fc7 write \u5199\u5165\u7684\u6570\u636e<\/li>\n
- \u5f53\u53ea\u6709\u4e00\u4e2a\u7ebf\u7a0b\u65f6，accpet\u3001read\u3001write \u53ea\u8981\u6709\u4e00\u4e2a\u963b\u585e，\u5c31\u4e0d\u80fd\u7ee7\u7eed\u8fd0\u884c\u4e86<\/li>\n
- IO \u591a\u8def\u8f6c\u63a5\u5b9e\u9645\u4e0a\u5c31\u662f\u5c06\u672c\u8be5\u7531\u7528\u6237\u8fdb\u884c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u8bfb\/\u5199\u7f13\u51b2\u533a\u7684\u68c0\u6d4b\u4ea4\u7ed9\u4e86\u5185\u6838，\u5185\u6838\u53ef\u4ee5\u540c\u65f6\u68c0\u6d4b\u82e5\u5e72\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u4ee5\u53ca\u5b83\u4eec\u7684\u8bfb\/\u5199\u7f13\u51b2\u533a，\u68c0\u6d4b\u8bfb\u7f13\u51b2\u533a\u662f\u5426\u6709\u6570\u636e\/\u68c0\u6d4b\u5199\u7f13\u51b2\u533a\u662f\u5426\u6709\u5269\u4f59\u7684\u7a7a\u95f4，\u5f53\u6761\u4ef6\u6ee1\u8db3\u65f6，\u5185\u6838\u4f1a\u544a\u77e5\u7528\u6237\u76f8\u5173\u4fe1\u606f（\u53ef\u64cd\u4f5c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26），\u6b64\u65f6 accpet\u3001read\u3001write \u5c31\u4e0d\u4f1a\u963b\u585e\u4e86，\u82e5\u5185\u6838\u901a\u77e5\u591a\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26，\u5728\u7528\u6237\u7a7a\u95f4\u5904\u7406\u65f6\u662f\u6309\u987a\u5e8f\u5904\u7406\u7684<\/li>\n<\/ul>\n
select<\/h2>\n
- \n
select\u80fd\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4e2a\u6570\u53d7\u9650\u4e8eFD_SETSIZE,\u4e00\u822c\u4e3a1024，\u5355\u7eaf\u6539\u53d8\u8fdb\u7a0b\u6253\u5f00\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4e2a\u6570\u5e76\u4e0d\u80fd\u6539\u53d8select\u76d1\u542c\u6587\u4ef6\u4e2a\u6570<\/p>\n<\/li>\n
- \n
\u89e3\u51b31024\u4ee5\u4e0b\u5ba2\u6237\u7aef\u65f6\u4f7f\u7528select\u662f\u5f88\u5408\u9002\u7684，\u4f46\u5982\u679c\u94fe\u63a5\u5ba2\u6237\u7aef\u8fc7\u591a，select\u91c7\u7528\u7684\u662f\u8f6e\u8be2\u6a21\u578b，\u4f1a\u5927\u5927\u964d\u4f4e\u670d\u52a1\u5668\u54cd\u5e94\u6548\u7387，\u4e0d\u5e94\u5728select\u4e0a\u6295\u5165\u66f4\u591a\u7cbe\u529b<\/p>\n<\/li>\n
#include <sys\/select.h><\/p>\n
\/* According to earlier standards *\/<\/p>\n
#include <sys\/time.h><\/p>\n
#include <sys\/types.h><\/p>\n
#include <unistd.h><\/p>\n<\/p>\n
\/\/ \u8fd4\u56de\u503c\u5c31\u7eea\u63cf\u8ff0\u7b26\u7684\u6570\u76ee<\/p>\n
int select(int nfds, fd_set *readfds, fd_set *writefds,<\/p>\n
fd_set *exceptfds, struct timeval *timeout);<\/p>\n
nfds: \u76d1\u63a7\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u91cc\u6700\u5927\u6587\u4ef6\u63cf\u8ff0\u7b26\u52a01，\u56e0\u4e3a\u6b64\u53c2\u6570\u4f1a\u544a\u8bc9\u5185\u6838\u68c0\u6d4b\u524d\u591a\u5c11\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u72b6\u6001<\/p>\n
readfds： \u76d1\u63a7\u6709\u8bfb\u6570\u636e\u5230\u8fbe\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408，\u4f20\u5165\u4f20\u51fa\u53c2\u6570<\/p>\n
writefds： \u76d1\u63a7\u5199\u6570\u636e\u5230\u8fbe\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408，\u4f20\u5165\u4f20\u51fa\u53c2\u6570<\/p>\n
exceptfds： \u76d1\u63a7\u5f02\u5e38\u53d1\u751f\u8fbe\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408,\u5982\u5e26\u5916\u6570\u636e\u5230\u8fbe\u5f02\u5e38，\u4f20\u5165\u4f20\u51fa\u53c2\u6570<\/p>\n
timeout： \u5b9a\u65f6\u963b\u585e\u76d1\u63a7\u65f6\u95f4，3\u79cd\u60c5\u51b5<\/p>\n
1.NULL，\u6c38\u8fdc\u7b49\u4e0b\u53bb<\/p>\n
2.\u8bbe\u7f6etimeval，\u7b49\u5f85\u56fa\u5b9a\u65f6\u95f4<\/p>\n
3.\u8bbe\u7f6etimeval\u91cc\u65f6\u95f4\u5747\u4e3a0，\u68c0\u67e5\u63cf\u8ff0\u5b57\u540e\u7acb\u5373\u8fd4\u56de，\u8f6e\u8be2<\/p>\n<\/p>\n
struct timeval {<\/p>\n
long tv_sec; \/* seconds *\/<\/p>\n
long tv_usec; \/* microseconds *\/<\/p>\n
};<\/p>\n<\/p>\n
void FD_CLR(int fd, fd_set *set); \/\/\u628a\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u91ccfd\u6e050<\/p>\n
int FD_ISSET(int fd, fd_set *set); \/\/\u6d4b\u8bd5\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u91ccfd\u662f\u5426\u7f6e1<\/p>\n
void FD_SET(int fd, fd_set *set); \/\/\u628a\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u91ccfd\u4f4d\u7f6e1<\/p>\n
void FD_ZERO(fd_set *set); \/\/\u628a\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u91cc\u6240\u6709\u4f4d\u6e050<\/p>\n
\u793a\u4f8b\u56fe\u5982\u4e0b：<\/p>\n
![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/07\/20250729163610-6888f87a0de08.png\")
<\/p>\n\u8fd9\u4e2a\u56fe\u7684\u610f\u601d\u662f，\u5e94\u7528\u5c42\u5148\u628a\u8981\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u505a\u6807\u8bb01，\u4e4b\u540e\u518d\u5c06\u5176\u62f7\u8d1d\u4e00\u4efd，\u5c06\u62f7\u8d1d\u7684\u8fd9\u4e00\u4efd\u6587\u4ef6\u63cf\u8ff0\u7b26\u5728\u62f7\u8d1d\u5230\u5185\u6838\u4e2d，\u8ba9\u5185\u6838\u76d1\u542c\u8fd9\u4e9b\u505a\u6807\u8bb0\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26，\u5982\u679c\u88ab\u76d1\u542c\u7684\u6587\u4ef6\u6ca1\u6709\u53d8\u5316，\u90a3\u4e48\u5185\u6838\u4e2d\u7684\u6587\u4ef6\u63cf\u8ff0\u7684\u6807\u8bb0\u5c31\u4f1a\u88ab\u62b9\u6d88，\u7136\u540e\u5728\u5c06\u6539\u53d8\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u590d\u5236\u5230\u5e94\u7528\u5c42，\u8ba9\u5176\u5bf9\u6539\u53d8\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u8fdb\u884c\u8bfb\u53d6，<\/p>\n
\u4f8b\u5982\u5e94\u7528\u5c42\u51c6\u5907\u76d1\u542c4567\u8fd9\u56db\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26，\u590d\u5236\u5230\u5185\u6838\u53bb\u76d1\u542c，\u5185\u6838\u53d1\u73b0\u53ea\u67095\u53f7\u53d1\u751f\u4e86\u6539\u53d8，\u6240\u4ee5\u544a\u77e5\u5e94\u7528\u5c42\u53bb5\u53f7\u6587\u4ef6\u63cf\u8ff0\u7b26\u8bfb\u53d6\u6570\u636e，\u5982\u679c\u662flfd\u53734\u53d1\u751f\u4e86\u53d8\u5316，\u5c31\u8bf4\u660e\u6709\u65b0\u7684\u8fde\u63a5\u4ea7\u751f\u4e86<\/p>\n
\n
server<\/h3>\n
\u6d41\u7a0b\u56fe\u793a：<\/p>\n
![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/07\/20250729163611-6888f87b7dd63.png\")
<\/p>\n#include <stdio.h>
\n#include <sys\/select.h> \/\/ select\u591a\u8def\u590d\u7528API
\n#include <sys\/types.h>\/\/ \u57fa\u672c\u7cfb\u7edf\u6570\u636e\u7c7b\u578b
\n#include <unistd.h>\/\/ POSIX API（read\/write\/close\u7b49）
\n#include "wrap.h"\/\/ \u81ea\u5b9a\u4e49\u9519\u8bef\u5904\u7406\u51fd\u6570\u5c01\u88c5
\n#include <sys\/time.h><\/p>\n#define PORT 8888 \/\/ \u670d\u52a1\u5668\u76d1\u542c\u7aef\u53e3<\/p>\n
int main(int argc, char *argv[])
\n{
\n\/\/ \u521b\u5efaTCP\u5957\u63a5\u5b57\u5e76\u7ed1\u5b9a\u7aef\u53e3
\nint lfd = tcp4bind(PORT, NULL);
\n\/\/ \u8bbe\u7f6e\u76d1\u542c\u961f\u5217\u957f\u5ea6\u4e3a128
\nListen(lfd, 128);<\/p>\nint maxfd = lfd; \/\/ \u521d\u59cb\u5316\u6700\u5927\u6587\u4ef6\u63cf\u8ff0\u7b26（\u5f53\u524d\u53ea\u6709\u76d1\u542c\u5957\u63a5\u5b57）
\nfd_set oldset, rset; \/\/ \u5b9a\u4e49\u4e24\u4e2afd_set：
\n \/\/ oldset：\u6c38\u4e45\u8bb0\u5f55\u6240\u6709\u9700\u76d1\u63a7\u7684fd
\n \/\/ rset：\u6bcf\u6b21select\u8c03\u7528\u4f20\u5165\u7684\u4e34\u65f6\u96c6\u5408<\/p>\nFD_ZERO(&oldset); \/\/ \u6e05\u7a7a\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408
\nFD_ZERO(&rset);
\nFD_SET(lfd, &oldset); \/\/ \u5c06\u76d1\u542c\u5957\u63a5\u5b57\u52a0\u5165\u76d1\u63a7\u96c6\u5408<\/p>\nwhile (1)
\n{
\nrset = oldset; \/\/ \u590d\u5236\u6c38\u4e45\u96c6\u5408\u5230\u4e34\u65f6\u96c6\u5408（select\u4f1a\u4fee\u6539\u4f20\u5165\u7684\u96c6\u5408）<\/p>\n\/\/ \u6838\u5fc3：\u963b\u585e\u76d1\u542c\u6240\u6709\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u53ef\u8bfb\u4e8b\u4ef6
\nint n = select(maxfd + 1, &rset, NULL, NULL, NULL);<\/p>\n\/\/ \u9519\u8bef\u5904\u7406
\nif (n < 0)
\n{
\nperror("select error");
\nbreak;
\n}
\nelse if (n == 0)
\n{ \/\/ \u65e0\u4e8b\u4ef6\u53d1\u751f（\u8d85\u65f6）
\ncontinue;
\n}<\/p>\n\/\/ \u5904\u7406\u76d1\u542c\u5957\u63a5\u5b57\u4e8b\u4ef6（\u65b0\u8fde\u63a5\u5230\u8fbe）\u67e5\u770blfd\u76d1\u542c\u63cf\u8ff0\u7b26\u662f\u5426\u5728\u5c31\u7eea\u7684rset\u96c6\u5408\u4e2d，\u5728\u8868\u793a\u6709\u65b0\u8fde\u63a5
\nif (FD_ISSET(lfd, &rset))
\n{ \/\/ \u68c0\u67e5\u76d1\u542c\u5957\u63a5\u5b57\u662f\u5426\u5c31\u7eea
\nstruct sockaddr_in cliaddr;
\nsocklen_t len = sizeof(cliaddr);
\nchar ip[16] = "";<\/p>\n\/\/ \u63a5\u53d7\u65b0\u8fde\u63a5
\nint cfd = Accept(lfd, (struct sockaddr *)&cliaddr, &len);
\nprintf("new client ip=%s port=%d\\\\n",
\n inet_ntop(AF_INET, &cliaddr.sin_addr.s_addr, ip, 16),
\n ntohs(cliaddr.sin_port));<\/p>\n\/\/ \u5c06\u65b0\u8fde\u63a5\u52a0\u5165\u6c38\u4e45\u76d1\u63a7\u96c6\u5408
\nFD_SET(cfd, &oldset);
\n\/\/ \u66f4\u65b0\u6700\u5927\u6587\u4ef6\u63cf\u8ff0\u7b26
\nif (cfd > maxfd)
\nmaxfd = cfd;<\/p>\n\/\/ \u82e5\u5df2\u65e0\u5176\u4ed6\u4e8b\u4ef6，\u8df3\u8fc7\u540e\u7eed\u5904\u7406
\nif (–n == 0)
\ncontinue;
\n}<\/p>\n\/\/ \u5904\u7406\u5df2\u8fde\u63a5\u5957\u63a5\u5b57\u7684\u6570\u636e\u4e8b\u4ef6
\n\/\/\u5728 Unix\/Linux \u4e2d，\u6587\u4ef6\u63cf\u8ff0\u7b26\u6309\u4ece\u5c0f\u5230\u5927\u7684\u987a\u5e8f\u5206\u914d\u3002lfd \u662f\u670d\u52a1\u5668\u542f\u52a8\u65f6\u6700\u65e9\u521b\u5efa\u7684\u5957\u63a5\u5b57，\u5176\u503c\u901a\u5e38\u4e3a3（0-2 \u88ab\u6807\u51c6\u8f93\u5165\/\u8f93\u51fa\/\u9519\u8bef\u5360\u7528），\u540e\u7eed cfd \u4f9d\u6b21\u9012\u589e（4, 5, …）
\n \/\/\u56e0\u6b64 lfd + 1 \u81ea\u7136\u6307\u5411\u7b2c\u4e00\u4e2a\u5ba2\u6237\u7aef\u8fde\u63a5\u5957\u63a5\u5b57\u3002
\nfor (int i = lfd + 1; i <= maxfd; i++)
\n{
\nif (FD_ISSET(i, &rset))
\n{ \/\/ \u68c0\u67e5\u5f53\u524dfd\u662f\u5426\u5c31\u7eea
\nchar buf[1500] = "";
\nint ret = Read(i, buf, sizeof(buf)); \/\/ \u8bfb\u53d6\u6570\u636e<\/p>\n\/\/ \u9519\u8bef\u5904\u7406
\nif (ret < 0)
\n{
\nperror("read error");
\nclose(i);
\nFD_CLR(i, &oldset); \/\/ \u4ece\u76d1\u63a7\u96c6\u5408\u79fb\u9664
\n}
\n\/\/ \u5ba2\u6237\u7aef\u5173\u95ed\u8fde\u63a5
\nelse if (ret == 0)
\n{
\nstruct sockaddr_in remote_addr;
\nsocklen_t len = sizeof(remote_addr);
\ngetpeername(i, (struct sockaddr *)&remote_addr, &len);
\nint remote_port = ntohs(remote_addr.sin_port);<\/p>\nprintf("client%d close\\\\n",remote_port);
\nclose(i);
\nFD_CLR(i, &oldset);
\n}
\n\/\/ \u6b63\u5e38\u6570\u636e\u5904\u7406
\nelse
\n{
\nstruct sockaddr_in remote_addr;
\nsocklen_t len = sizeof(remote_addr);
\ngetpeername(i, (struct sockaddr *)&remote_addr, &len);
\nint remote_port = ntohs(remote_addr.sin_port);<\/p>\nprintf("\u5ba2\u6237\u7aef%d:%s\\\\n", remote_port,buf);
\nWrite(i, buf, ret); \/\/ \u56de\u663e\u6570\u636e
\n}
\n}
\n}
\n}
\nreturn 0;
\n}<\/p>\n\u51e0\u4e2a\u95ee\u9898？<\/p>\n
1.select(maxfd + 1, &rset, NULL, NULL, NULL);\u4e3a\u4ec0\u4e48\u8981maxfd + 1？<\/p>\n
fd_set rset;
\nint maxfd = 5; \u00a0\/\/ \u5f53\u524d\u6700\u5927FD\u4e3a5
\nFD_ZERO(&rset);
\nFD_SET(3, &rset); \u00a0\/\/ \u76d1\u63a7FD=3
\nFD_SET(5, &rset); \u00a0\/\/ \u76d1\u63a7FD=5<\/p>\n\/\/ \u5185\u6838\u4f1a\u68c0\u67e50~5\u7684FD（\u51716\u4e2a），\u4f46\u4ec5FD=3\u548c5\u5b9e\u9645\u88ab\u76d1\u63a7
\nselect(5 + 1, &rset, NULL, NULL, NULL);<\/p>\n\u82e5\u8bef\u4f20\u00a0maxfd=5（\u672a+1），\u5185\u6838\u53ef\u80fd\u6f0f\u68c0FD=5，\u5bfc\u81f4\u6570\u636e\u5c31\u7eea\u5374\u672a\u88ab\u89e6\u53d1<\/p>\n<\/p>\n
2.int n = select(maxfd + 1, &rset, NULL, NULL, NULL);\u8fd9\u91cc\u662f\u600e\u6837\u904d\u5386\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u7684？\u662f\u4ece0\u5f00\u59cb\u904d\u5386rset\u91cc\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u5417？<\/p>\n
- \n
- \u5728\u00a0select\u00a0\u51fd\u6570\u4e2d，\u5185\u6838\u904d\u5386\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408（rset）\u7684\u65b9\u5f0f\u662f\u901a\u8fc7\u7ebf\u6027\u626b\u63cf\u4f4d\u56fe，\u4ece\u6587\u4ef6\u63cf\u8ff0\u7b26 \u200b0\u200b \u5f00\u59cb，\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u6bd4\u7279\u4f4d\u662f\u5426\u88ab\u7f6e\u4f4d（\u5373\u662f\u5426\u4e3a1），\u76f4\u5230\u8fbe\u5230\u00a0maxfd + 1\u00a0\u6307\u5b9a\u7684\u8303\u56f4\u3002\u4ece0\u5230\u00a0maxfd，\u65e0\u8bba\u6587\u4ef6\u63cf\u8ff0\u7b26\u662f\u5426\u6253\u5f00\u6216\u6d3b\u8dc3\u3002\u8fd9\u79cd\u8bbe\u8ba1\u7b80\u5355\u4f46\u6548\u7387\u4f4e，\u662f\u00a0select\u00a0\u88ab\u00a0epoll\u00a0\u53d6\u4ee3\u7684\u4e3b\u8981\u539f\u56e0\u4e4b\u4e00<\/li>\n<\/ul>\n
3.select(maxfd + 1, &rset, NULL, NULL, NULL);\u91cc\u7684rset\u4f5c\u7528\u662f\u4ec0\u4e48<\/p>\n
- \n
- \u5728\u00a0select\u00a0\u51fd\u6570\u4e2d，rset\u00a0\u662f\u4e00\u4e2a\u00a0fd_set\u00a0\u7c7b\u578b\u7684\u4f4d\u56fe\u96c6\u5408，\u5176\u6838\u5fc3\u4f5c\u7528\u662f\u6807\u8bc6\u9700\u8981\u76d1\u63a7\u7684\u53ef\u8bfb\u6587\u4ef6\u63cf\u8ff0\u7b26（FD）\u96c6\u5408，\u5e76\u5728\u51fd\u6570\u8fd4\u56de\u65f6\u6807\u8bb0\u54ea\u4e9bFD\u5df2\u5c31\u7eea\u53ef\u8bfb\u3002<\/li>\n<\/ul>\n
4.for (int i = lfd + 1; i <= maxfd; i++) \u4e3a\u4ec0\u4e48\u4ece lfd + 1\u5f00\u59cb\u904d\u5386？\u200b<\/p>\n
- \n
- \u200blfd\u00a0\u901a\u5e38\u662f\u8f83\u5c0f\u7684\u503c：
\n\u5728 Unix\/Linux \u4e2d，\u6587\u4ef6\u63cf\u8ff0\u7b26\u6309\u4ece\u5c0f\u5230\u5927\u7684\u987a\u5e8f\u5206\u914d\u3002lfd\u00a0\u662f\u670d\u52a1\u5668\u542f\u52a8\u65f6\u6700\u65e9\u521b\u5efa\u7684\u5957\u63a5\u5b57，\u5176\u503c\u901a\u5e38\u4e3a3（0-2 \u88ab\u6807\u51c6\u8f93\u5165\/\u8f93\u51fa\/\u9519\u8bef\u5360\u7528），\u540e\u7eed\u00a0cfd\u00a0\u4f9d\u6b21\u9012\u589e（4, 5, …）\u3002<\/li>\n - \n\u56e0\u6b64\u00a0lfd + 1\u00a0\u81ea\u7136\u6307\u5411\u7b2c\u4e00\u4e2a\u5ba2\u6237\u7aef\u8fde\u63a5\u5957\u63a5\u5b57\u3002<\/li>\n<\/ul>\n
client<\/h3>\n
\u5ba2\u6237\u7aef\u4f7f\u7528：<\/p>\n
nc 127.0.0.1 8888<\/p>\n
\u6a21\u62df\u5ba2\u6237\u7aef\u94fe\u63a5\u670d\u52a1\u5668<\/p>\n
\u7ed3\u679c\u663e\u793a\u5982\u4e0b：<\/p>\n
![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/07\/20250729163616-6888f880eab11.png\")
<\/p>\n\u4f46\u8fd9\u6837\u6709\u4e2a\u95ee\u9898，\u65e0\u8bba\u8fde\u63a5\u670d\u52a1\u5668\u7684\u5ba2\u6237\u7aef\u662f\u5426\u6d3b\u8dc3，\u904d\u5386\u65f6\u90fd\u4f1a\u904d\u5386\u8fd9\u4e9b\u8fde\u63a5\u7684\u5ba2\u6237\u7aef，\u6240\u4ee5\u8fd9\u5c31\u4f1a\u5f15\u53d1\u4e00\u4e2a\u95ee\u9898（\u5927\u91cf\u5e76\u53d1<\/span>,<\/span>\u5c11\u4e86\u6d3b\u8dc3<\/span>）：<\/p>\n
\u5047\u8bbe\u73b0\u5728 4-1023\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u9700\u8981\u76d1\u542c,\u4f46\u662f5-1000\u8fd9\u4e9b\u6587\u4ef6\u63cf\u8ff0\u7b26\u5173\u95ed\u4e86，\u904d\u5386\u65f6\u8fd8\u662f\u8981\u4ece4-1023\u8fdb\u884c\u904d\u5386，\u5b9e\u9645\u53ea\u9700\u8981\u904d\u53864\u30011001-1023\u5373\u53ef\u3002<\/p>\n
\u5047\u8bbe\u73b0\u5728 4-1023\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u9700\u8981\u76d1\u542c,\u4f46\u662f\u53ea\u6709 5,1002 \u53d1\u6765\u6d88\u606f，\u904d\u5386\u65f6\u8fd8\u662f\u8981\u4ece4-1023\u8fdb\u884c\u904d\u5386，\u5b9e\u9645\u53ea\u9700\u8981\u904d\u53865\u30011002\u5373\u53ef\u3002<\/p>\n
select\u8fdb\u9636\u4f18\u5316\u7248<\/h3>\n
\u4e4b\u524d\u7684\u4ee3\u7801，\u5982\u679c\u6700\u5927fd\u662f1023，\u6bcf\u6b21\u786e\u5b9a\u6709\u4e8b\u4ef6\u53d1\u751f\u7684fd\u65f6，\u5c31\u8981\u626b\u63cf3-1023\u7684\u6240\u6709\u6587\u4ef6\u63cf\u8ff0\u7b26，\u8fd9\u770b\u8d77\u6765\u5f88\u8822\u3002\u4e8e\u662f\u5b9a\u4e49\u4e00\u4e2a\u6570\u7ec4，\u628a\u8981\u76d1\u542c\u7684\u6d3b\u8dc3\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u5b58\u4e0b\u6765，\u6bcf\u6b21\u626b\u63cf\u8fd9\u4e2a\u6570\u7ec4\u5c31\u884c\u4e86\u3002\u770b\u8d77\u6765\u79d1\u5b66\u5f97\u591a\u3002<\/span><\/p>\n
server<\/h3>\n
\/\/\u8fdb\u9636\u7248select，\u901a\u8fc7\u6570\u7ec4\u9632\u6b62\u904d\u53861024\u4e2a\u63cf\u8ff0\u7b26
\n#include <stdio.h>
\n#include <stdlib.h>
\n#include <unistd.h>
\n#include <string.h>
\n#include <arpa\/inet.h>
\n#include <ctype.h><\/p>\n#include "wrap.h"<\/p>\n
#define SERV_PORT 8888<\/p>\n
int main(int argc, char *argv[])
\n{
\n int i, j, n, maxi;<\/p>\nint nready, client[FD_SETSIZE]; \/* \u81ea\u5b9a\u4e49\u6570\u7ec4client, \u9632\u6b62\u904d\u53861024\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26 FD_SETSIZE\u9ed8\u8ba4\u4e3a1024 *\/
\n int maxfd, listenfd, connfd, sockfd;
\n char buf[BUFSIZ], str[INET_ADDRSTRLEN]; \/* #define INET_ADDRSTRLEN 16 *\/
\n struct sockaddr_in clie_addr, serv_addr;
\n socklen_t clie_addr_len;
\n fd_set rset, allset; \/* rset \u8bfb\u4e8b\u4ef6\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408 allset\u7528\u6765\u6682\u5b58 *\/<\/p>\nlistenfd = Socket(AF_INET, SOCK_STREAM, 0);
\n \/\/\u7aef\u53e3\u590d\u7528
\n int opt = 1;
\n setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));<\/p>\nbzero(&serv_addr, sizeof(serv_addr));
\n serv_addr.sin_family= AF_INET;
\n serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
\n serv_addr.sin_port= htons(SERV_PORT);<\/p>\nBind(listenfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr));
\n Listen(listenfd, 128);<\/p>\nmaxfd = listenfd; \/* \u8d77\u521d listenfd \u5373\u4e3a\u6700\u5927\u6587\u4ef6\u63cf\u8ff0\u7b26 *\/<\/p>\n
maxi = -1; \/* \u5c06\u6765\u7528\u4f5cclient[]\u7684\u4e0b\u6807, \u521d\u59cb\u503c\u6307\u54110\u4e2a\u5143\u7d20\u4e4b\u524d\u4e0b\u6807\u4f4d\u7f6e *\/
\n for (i = 0; i < FD_SETSIZE; i++)
\n client[i] = -1; \/* \u7528-1\u521d\u59cb\u5316client[] *\/<\/p>\nFD_ZERO(&allset);
\n FD_SET(listenfd, &allset); \/* \u6784\u9020select\u76d1\u63a7\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6 *\/<\/p>\nwhile (1) {
\n rset = allset; \/* \u6bcf\u6b21\u5faa\u73af\u65f6\u90fd\u4ece\u65b0\u8bbe\u7f6eselect\u76d1\u63a7\u4fe1\u53f7\u96c6 *\/<\/p>\nnready = select(maxfd+1, &rset, NULL, NULL, NULL); \/\/2 1–lfd 1–connfd
\n if (nready < 0)
\n perr_exit("select error");<\/p>\nif (FD_ISSET(listenfd, &rset)) { \/* \u8bf4\u660e\u6709\u65b0\u7684\u5ba2\u6237\u7aef\u94fe\u63a5\u8bf7\u6c42 *\/<\/p>\n
clie_addr_len = sizeof(clie_addr);
\n connfd = Accept(listenfd, (struct sockaddr *)&clie_addr, &clie_addr_len); \/* Accept \u4e0d\u4f1a\u963b\u585e *\/
\n printf("received from %s at PORT %d\\\\n",
\n inet_ntop(AF_INET, &clie_addr.sin_addr, str, sizeof(str)),
\n ntohs(clie_addr.sin_port));<\/p>\nfor (i = 0; i < FD_SETSIZE; i++)
\n if (client[i] < 0) { \/* \u627eclient[]\u4e2d\u6ca1\u6709\u4f7f\u7528\u7684\u4f4d\u7f6e *\/
\n client[i] = connfd; \/* \u4fdd\u5b58accept\u8fd4\u56de\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u5230client[]\u91cc *\/
\n break;
\n }<\/p>\nif (i == FD_SETSIZE) { \/* \u8fbe\u5230select\u80fd\u76d1\u63a7\u7684\u6587\u4ef6\u4e2a\u6570\u4e0a\u9650 1024 *\/
\n fputs("too many clients\\\\n", stderr);
\n exit(1);
\n }<\/p>\nFD_SET(connfd, &allset); \/* \u5411\u76d1\u63a7\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408allset\u6dfb\u52a0\u65b0\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26connfd *\/<\/p>\n
if (connfd > maxfd)
\n maxfd = connfd; \/* select\u7b2c\u4e00\u4e2a\u53c2\u6570\u9700\u8981 *\/<\/p>\nif (i > maxi)
\n maxi = i; \/* \u4fdd\u8bc1maxi\u5b58\u7684\u603b\u662fclient[]\u6700\u540e\u4e00\u4e2a\u5143\u7d20\u4e0b\u6807 *\/<\/p>\nif (–nready == 0)
\n continue;
\n } <\/p>\nfor (i = 0; i <= maxi; i++) { \/* \u68c0\u6d4b\u54ea\u4e2aclients \u6709\u6570\u636e\u5c31\u7eea *\/<\/p>\n
if ((sockfd = client[i]) < 0)
\n continue;\/\/\u6570\u7ec4\u5185\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u5982\u679c\u88ab\u91ca\u653e\u6709\u53ef\u80fd\u53d8\u6210-1
\n if (FD_ISSET(sockfd, &rset)) {<\/p>\nif ((n = Read(sockfd, buf, sizeof(buf))) == 0) { \/* \u5f53client\u5173\u95ed\u94fe\u63a5\u65f6,\u670d\u52a1\u5668\u7aef\u4e5f\u5173\u95ed\u5bf9\u5e94\u94fe\u63a5 *\/
\n Close(sockfd);
\n FD_CLR(sockfd, &allset); \/* \u89e3\u9664select\u5bf9\u6b64\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u76d1\u63a7 *\/
\n client[i] = -1;
\n } else if (n > 0) {
\n for (j = 0; j < n; j++)
\n buf[j] = toupper(buf[j]);
\n Write(sockfd, buf, n);
\n Write(STDOUT_FILENO, buf, n);
\n }
\n if (–nready == 0)
\n break; \/* \u8df3\u51fafor, \u4f46\u8fd8\u5728while\u4e2d *\/
\n }
\n }
\n }<\/p>\nClose(listenfd);<\/p>\n
return 0;
\n}<\/p>\n\u82e5\u00a0lfd = 3，maxfd = 100，\u4f46\u4ec5 5 \u4e2a\u6d3b\u8dc3\u8fde\u63a5，\u57fa\u7840\u7248\u4ecd\u9700\u5faa\u73af 97 \u6b21（4~100），\u800c\u8fdb\u9636\u7248\u4ec5\u9700\u5faa\u73af 5 \u6b21（\u6570\u7ec4\u4e2d\u7684\u6d3b\u8dc3 FD）\u3002<\/p>\n
\u5c40\u9650\u6027<\/h3>\n
\n\u867d\u7136\u4f7f\u7528 select \u8fd9\u79cd IO \u591a\u8def\u8f6c\u63a5\u6280\u672f\u53ef\u4ee5\u964d\u4f4e\u7cfb\u7edf\u5f00\u9500，\u63d0\u9ad8\u7a0b\u5e8f\u6548\u7387，\u4f46\u662f\u5b83\u4e5f\u6709\u5c40\u9650\u6027：<\/p>\n
\n
\u5f85\u68c0\u6d4b\u96c6\u5408（\u7b2c 2\u30013\u30014 \u4e2a\u53c2\u6570）\u9700\u8981\u9891\u7e41\u7684\u5728\u7528\u6237\u533a\u548c\u5185\u6838\u533a\u4e4b\u95f4\u8fdb\u884c\u6570\u636e\u7684\u62f7\u8d1d，\u6548\u7387\u4f4e<\/p>\n
\u5185\u6838\u5bf9\u4e8e select \u4f20\u9012\u8fdb\u6765\u7684\u5f85\u68c0\u6d4b\u96c6\u5408\u7684\u68c0\u6d4b\u65b9\u5f0f\u662f\u7ebf\u6027\u7684<\/p>\n
\u68c0\u6d4b\u6548\u7387\u4e0e\u96c6\u5408\u5185\u5f85\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u6709\u5173：\u5982\u679c\u96c6\u5408\u5185\u5f85\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u5f88\u591a，\u68c0\u6d4b\u6548\u7387\u4f1a\u6bd4\u8f83\u4f4e；\u5982\u679c\u96c6\u5408\u5185\u5f85\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u76f8\u5bf9\u8f83\u5c11，\u68c0\u6d4b\u6548\u7387\u4f1a\u6bd4\u8f83\u9ad8<\/p>\n
\u4f7f\u7528 select \u80fd\u591f\u68c0\u6d4b\u7684\u6700\u5927\u6587\u4ef6\u63cf\u8ff0\u7b26\u4e2a\u6570\u6709\u4e0a\u9650，\u9ed8\u8ba4\u662f 1024，\u8fd9\u662f\u5728\u5185\u6838\u4e2d\u88ab\u5199\u6b7b\u4e86\u7684<\/p>\n
\n
poll<\/h2>\n
poll \u7684\u673a\u5236\u4e0e select \u7c7b\u4f3c，\u4e0e select \u5728\u672c\u8d28\u4e0a\u6ca1\u6709\u591a\u5927\u5dee\u522b，\u4f7f\u7528\u65b9\u6cd5\u4e5f\u7c7b\u4f3c，\u4e0b\u9762\u7684\u662f\u5bf9\u4e8e\u4e8c\u8005\u7684\u5bf9\u6bd4：<\/p>\n
- \n
- \u5185\u6838\u5bf9\u5e94\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u68c0\u6d4b\u4e5f\u662f\u4ee5\u7ebf\u6027\u7684\u65b9\u5f0f\u8fdb\u884c\u8f6e\u8be2，\u6839\u636e\u63cf\u8ff0\u7b26\u7684\u72b6\u6001\u8fdb\u884c\u5904\u7406<\/li>\n
- poll \u548c select \u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u4f1a\u5728\u68c0\u6d4b\u8fc7\u7a0b\u4e2d\u9891\u7e41\u7684\u8fdb\u884c\u7528\u6237\u533a\u548c\u5185\u6838\u533a\u7684\u62f7\u8d1d，\u5b83\u7684\u5f00\u9500\u968f\u7740\u6587\u4ef6\u63cf\u8ff0\u7b26\u6570\u91cf\u7684\u589e\u52a0\u800c\u7ebf\u6027\u589e\u5927，\u4ece\u800c\u6548\u7387\u4e5f\u4f1a\u8d8a\u6765\u8d8a\u4f4e\u3002<\/li>\n
- select \u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4e2a\u6570\u4e0a\u9650\u662f 1024，poll \u6ca1\u6709\u6700\u5927\u6587\u4ef6\u63cf\u8ff0\u7b26\u6570\u91cf\u7684\u9650\u5236<\/li>\n
- select \u53ef\u4ee5\u8de8\u5e73\u53f0\u4f7f\u7528，poll \u53ea\u80fd\u5728 Linux \u5e73\u53f0\u4f7f\u7528<\/li>\n
- select \u901a\u8fc7 fd_set（\u4f4d\u56fe\u96c6\u5408）\u6765\u8bb0\u5f55\u6587\u4ef6\u63cf\u8ff0\u7b26，poll \u4f7f\u7528\u4e00\u4e2a\u6574\u578b\u6570\u6765\u8bb0\u5f55<\/li>\n<\/ul>\n
\npoll \u51fd\u6570<\/p>\n
#include <poll.h>
\n\/\/ \u6bcf\u4e2a\u59d4\u6258poll\u68c0\u6d4b\u7684fd\u90fd\u5bf9\u5e94\u8fd9\u6837\u4e00\u4e2a\u7ed3\u6784\u4f53
\nstruct pollfd {
\n\u00a0 \u00a0 int \u00a0 fd; \u00a0 \u00a0 \u00a0 \u00a0 \/* \u59d4\u6258\u5185\u6838\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26 *\/
\n\u00a0 \u00a0 short events; \u00a0 \u00a0 \/* \u59d4\u6258\u5185\u6838\u68c0\u6d4b\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u4ec0\u4e48\u4e8b\u4ef6 *\/
\n\u00a0 \u00a0 short revents; \u00a0 \u00a0\/* \u6587\u4ef6\u63cf\u8ff0\u7b26\u5b9e\u9645\u53d1\u751f\u7684\u4e8b\u4ef6 -> \u4f20\u51fa *\/ \u00a0\/\/ \u4e0d\u9700\u8981\u8fdb\u884c\u521d\u59cb\u5316
\n};<\/p>\nstruct pollfd myfd[100]; \u00a0 \/\/ \u53ef\u80fd\u9700\u8981\u68c0\u6d4b\u82e5\u5e72\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26，\u8981\u5b58\u50a8\u5728\u6570\u7ec4\u4e2d
\nint poll(struct pollfd *fds, nfds_t nfds, int timeout);
\n\u00a0<\/p>\n\n\u53c2\u6570\u542b\u4e49：<\/p>\n
\nfds: \u8fd9\u662f\u4e00\u4e2a struct pollfd \u7c7b\u578b\u7684\u6570\u7ec4, \u91cc\u8fb9\u5b58\u50a8\u4e86\u5f85\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u4fe1\u606f，\u8fd9\u4e2a\u6570\u7ec4\u4e2d\u6709\u4e09\u4e2a\u6210\u5458：<\/p>\n
fd：\u59d4\u6258\u5185\u6838\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26
\nevents：\u59d4\u6258\u5185\u6838\u68c0\u6d4b\u7684 fd \u4e8b\u4ef6（\u8f93\u5165\u3001\u8f93\u51fa\u3001\u9519\u8bef），\u6bcf\u4e00\u4e2a\u4e8b\u4ef6\u6709\u591a\u4e2a\u53d6\u503c
\nrevents：\u8fd9\u662f\u4e00\u4e2a\u4f20\u51fa\u53c2\u6570，\u6570\u636e\u7531\u5185\u6838\u5199\u5165，\u5b58\u50a8\u5185\u6838\u68c0\u6d4b\u4e4b\u540e\u7684\u7ed3\u679c（\u4e0d\u9700\u8981\u521d\u59cb\u5316，\u6839\u636e events \u59d4\u6258\u5185\u6838\u68c0\u6d4b\u7684\u65f6\u95f4\u4f20\u51fa\u7ed3\u679c）<\/p>\n![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/07\/20250729163619-6888f88302b0c.png\")
<\/p>\nnfds: \u8fd9\u662f\u7b2c\u4e00\u4e2a\u53c2\u6570\u6570\u7ec4\u4e2d\u6700\u540e\u4e00\u4e2a\u6709\u6548\u5143\u7d20\u7684\u4e0b\u6807 + 1（\u4e5f\u53ef\u4ee5\u6307\u5b9a\u53c2\u6570 1 \u6570\u7ec4\u7684\u5143\u7d20\u603b\u4e2a\u6570）<\/p>\n
timeout: \u6307\u5b9a poll \u51fd\u6570\u7684\u963b\u585e\u65f6\u957f<\/p>\n
-1：\u4e00\u76f4\u963b\u585e，\u76f4\u5230\u68c0\u6d4b\u7684\u96c6\u5408\u4e2d\u6709\u5c31\u7eea\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26（\u6709\u4e8b\u4ef6\u4ea7\u751f）\u89e3\u9664\u963b\u585e
\n0：\u4e0d\u963b\u585e，\u4e0d\u7ba1\u68c0\u6d4b\u96c6\u5408\u4e2d\u6709\u6ca1\u6709\u5df2\u5c31\u7eea\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26，\u51fd\u6570\u9a6c\u4e0a\u8fd4\u56de
\n\u5927\u4e8e 0：\u963b\u585e\u6307\u5b9a\u7684\u6beb\u79d2（ms）\u6570\u4e4b\u540e，\u89e3\u9664\u963b\u585e<\/p>\n\n\u8fd4\u56de\u503c：\u6210\u529f\u8fd4\u56de\u96c6\u5408\u4e2d\u5df2\u5c31\u7eea\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u603b\u4e2a\u6570，\u5931\u8d25\u8fd4\u56de-1<\/p>\n<\/p>\n
server<\/h3>\n
#include <stdio.h>
\n#include <stdlib.h>
\n#include <string.h>
\n#include <netinet\/in.h>
\n#include <arpa\/inet.h>
\n#include <poll.h>
\n#include <errno.h>
\n#include "wrap.h" \/\/ \u81ea\u5b9a\u4e49\u7684\u5305\u88f9\u51fd\u6570\u5934\u6587\u4ef6（\u5982Socket\u3001Bind\u7b49）<\/p>\n#define MAXLINE 80 \/\/ \u7f13\u51b2\u533a\u5927\u5c0f
\n#define SERV_PORT 6666 \/\/ \u670d\u52a1\u5668\u7aef\u53e3
\n#define OPEN_MAX 1024 \/\/ \u6700\u5927\u6587\u4ef6\u63cf\u8ff0\u7b26\u6570\u91cf<\/p>\nint main(int argc, char *argv[])
\n{
\n int i, j, maxi, listenfd, connfd, sockfd;
\n int nready; \/\/ poll\u8fd4\u56de\u7684\u5c31\u7eea\u6587\u4ef6\u63cf\u8ff0\u7b26\u6570\u91cf
\n ssize_t n; \/\/ \u8bfb\u53d6\u7684\u5b57\u8282\u6570
\n char buf[MAXLINE], str[INET_ADDRSTRLEN]; \/\/ \u7f13\u51b2\u533a\u548cIP\u5730\u5740\u5b57\u7b26\u4e32
\n socklen_t clilen; \/\/ \u5ba2\u6237\u7aef\u5730\u5740\u957f\u5ea6
\n struct pollfd client[OPEN_MAX]; \/\/ poll\u76d1\u63a7\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u6570\u7ec4
\n struct sockaddr_in cliaddr, servaddr; \/\/ \u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u5730\u5740\u7ed3\u6784<\/p>\n\/* 1. \u521b\u5efa\u76d1\u542c\u5957\u63a5\u5b57 *\/
\n listenfd = Socket(AF_INET, SOCK_STREAM, 0); \/\/ IPv4 TCP\u5957\u63a5\u5b57<\/p>\n\/* 2. \u7ed1\u5b9a\u670d\u52a1\u5668\u5730\u5740 *\/
\n bzero(&servaddr, sizeof(servaddr)); \/\/ \u6e05\u7a7a\u7ed3\u6784\u4f53
\n servaddr.sin_family = AF_INET; \/\/ IPv4
\n servaddr.sin_addr.s_addr = htonl(INADDR_ANY); \/\/ \u76d1\u542c\u6240\u6709\u672c\u5730IP
\n servaddr.sin_port = htons(SERV_PORT); \/\/ \u8bbe\u7f6e\u7aef\u53e3
\n Bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));<\/p>\n\/* 3. \u5f00\u59cb\u76d1\u542c *\/
\n Listen(listenfd, 20); \/\/ \u76d1\u542c\u961f\u5217\u6700\u5927\u957f\u5ea6\u4e3a20<\/p>\n\/* 4. \u521d\u59cb\u5316poll\u76d1\u63a7\u6570\u7ec4 *\/
\n client[0].fd = listenfd; \/\/ \u7b2c\u4e00\u4e2a\u5143\u7d20\u662f\u76d1\u542c\u5957\u63a5\u5b57
\n client[0].events = POLLRDNORM; \/\/ \u76d1\u542c\u666e\u901a\u8bfb\u4e8b\u4ef6（\u65b0\u8fde\u63a5）
\n for (i = 1; i < OPEN_MAX; i++)
\n client[i].fd = -1; \/\/ \u5176\u4f59\u5143\u7d20\u521d\u59cb\u5316\u4e3a-1（\u8868\u793a\u7a7a\u95f2）
\n maxi = 0; \/\/ \u5f53\u524dclient\u6570\u7ec4\u4e2d\u6709\u6548\u5143\u7d20\u7684\u6700\u5927\u4e0b\u6807<\/p>\n\/* 5. \u4e3b\u5faa\u73af：\u5904\u7406poll\u4e8b\u4ef6 *\/
\n for (;;)
\n {
\n \/\/ \u963b\u585e\u7b49\u5f85\u4e8b\u4ef6\u53d1\u751f，\u76d1\u63a7maxi+1\u4e2a\u63cf\u8ff0\u7b26（\u4ece0\u5230maxi），\u65e0\u9650\u7b49\u5f85
\n nready = poll(client, maxi + 1, -1);<\/p>\n\/* 5.1 \u5904\u7406\u76d1\u542c\u5957\u63a5\u5b57（\u65b0\u8fde\u63a5） *\/
\n if (client[0].revents & POLLRDNORM) \/\/ \u76d1\u542c\u5957\u63a5\u5b57\u53ef\u8bfb（\u6709\u65b0\u8fde\u63a5）
\n {
\n clilen = sizeof(cliaddr);
\n connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &clilen);
\n printf("received from %s at PORT %d\\\\n",
\n inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)),
\n ntohs(cliaddr.sin_port)); \/\/ \u6253\u5370\u5ba2\u6237\u7aefIP\u548c\u7aef\u53e3<\/p>\n\/* \u5c06\u65b0\u8fde\u63a5\u52a0\u5165client\u6570\u7ec4 *\/
\n for (i = 1; i < OPEN_MAX; i++)
\n {
\n if (client[i].fd < 0)
\n { \/\/ \u627e\u5230\u7b2c\u4e00\u4e2a\u7a7a\u95f2\u4f4d\u7f6e
\n client[i].fd = connfd; \/\/ \u5b58\u50a8\u65b0\u8fde\u63a5\u7684\u63cf\u8ff0\u7b26
\n break;
\n }
\n }<\/p>\nif (i == OPEN_MAX) \/\/ \u8d85\u8fc7\u6700\u5927\u8fde\u63a5\u6570\u9650\u5236
\n perr_exit("too many clients");<\/p>\nclient[i].events = POLLRDNORM; \/\/ \u5bf9\u65b0\u8fde\u63a5\u76d1\u63a7\u8bfb\u4e8b\u4ef6
\n if (i > maxi)
\n maxi = i; \/\/ \u66f4\u65b0\u6700\u5927\u6709\u6548\u4e0b\u6807<\/p>\nif (–nready <= 0) \/\/ \u5982\u679c\u6ca1\u6709\u66f4\u591a\u5c31\u7eea\u4e8b\u4ef6，\u7ee7\u7eedpoll
\n continue;
\n }<\/p>\n\/* 5.2 \u5904\u7406\u5df2\u8fde\u63a5\u5957\u63a5\u5b57\u7684\u6570\u636e *\/
\n for (i = 1; i <= maxi; i++) \/\/ \u904d\u5386\u6240\u6709\u53ef\u80fd\u7684\u8fde\u63a5
\n {
\n if ((sockfd = client[i].fd) < 0) \/\/ \u8df3\u8fc7\u65e0\u6548\u63cf\u8ff0\u7b26
\n continue;<\/p>\n\/* \u68c0\u67e5\u8bfb\u4e8b\u4ef6\u6216\u9519\u8bef\u4e8b\u4ef6 *\/
\n if (client[i].revents & (POLLRDNORM | POLLERR))
\n {
\n n = Read(sockfd, buf, MAXLINE); \/\/ \u8bfb\u53d6\u6570\u636e
\n if (n < 0)
\n {
\n \/\/ \u8bfb\u53d6\u9519\u8bef
\n if (errno == ECONNRESET) \/\/ \u5ba2\u6237\u7aef\u53d1\u9001RST\u91cd\u7f6e\u8fde\u63a5
\n {
\n printf("client[%d] aborted connection\\\\n", i);
\n Close(sockfd);
\n client[i].fd = -1; \/\/ \u91cd\u7f6e\u4e3a\u672a\u4f7f\u7528
\n }
\n else
\n {
\n perr_exit("read error"); \/\/ \u5176\u4ed6\u9519\u8bef\u76f4\u63a5\u9000\u51fa
\n }
\n }
\n else if (n == 0) \/\/ \u5ba2\u6237\u7aef\u5173\u95ed\u8fde\u63a5
\n {
\n printf("client[%d] closed connection\\\\n", i);
\n Close(sockfd);
\n client[i].fd = -1;
\n }
\n else \/\/ \u6b63\u5e38\u8bfb\u53d6\u6570\u636e
\n {
\n for (j = 0; j < n; j++) \/\/ \u8f6c\u4e3a\u5927\u5199
\n buf[j] = toupper(buf[j]);
\n Writen(sockfd, buf, n); \/\/ \u56de\u5199\u7ed9\u5ba2\u6237\u7aef
\n }<\/p>\nif (–nready <= 0) \/\/ \u6ca1\u6709\u66f4\u591a\u5c31\u7eea\u4e8b\u4ef6，\u8df3\u51fa\u5faa\u73af
\n break;
\n }
\n }
\n }
\n return 0;
\n}<\/p>\nclient<\/h3>\n
\u5ba2\u6237\u7aef\u4f7f\u7528：<\/p>\n
nc 127.0.0.1 6666<\/p>\n
\u6a21\u62df\u5ba2\u6237\u7aef\u94fe\u63a5\u670d\u52a1\u5668<\/p>\n<\/p>\n
epoll<\/h2>\n
epoll\u662fLinux\u4e0b\u591a\u8def\u590d\u7528IO\u63a5\u53e3select\/poll\u7684\u589e\u5f3a\u7248\u672c，\u5b83\u80fd\u663e\u8457\u63d0\u9ad8\u7a0b\u5e8f\u5728\u5927\u91cf\u5e76\u53d1\u8fde\u63a5\u4e2d\u53ea\u6709\u5c11\u91cf\u6d3b\u8dc3\u7684\u60c5\u51b5\u4e0b\u7684\u7cfb\u7edfCPU\u5229\u7528\u7387，\u56e0\u4e3a\u5b83\u4f1a\u590d\u7528\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u6765\u4f20\u9012\u7ed3\u679c\u800c\u4e0d\u7528\u8feb\u4f7f\u5f00\u53d1\u8005\u6bcf\u6b21\u7b49\u5f85\u4e8b\u4ef6\u4e4b\u524d\u90fd\u5fc5\u987b\u91cd\u65b0\u51c6\u5907\u8981\u88ab\u4fa6\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408，\u53e6\u4e00\u70b9\u539f\u56e0\u5c31\u662f\u83b7\u53d6\u4e8b\u4ef6\u7684\u65f6\u5019，\u5b83\u65e0\u987b\u904d\u5386\u6574\u4e2a\u88ab\u4fa6\u542c\u7684\u63cf\u8ff0\u7b26\u96c6，\u53ea\u8981\u904d\u5386\u90a3\u4e9b\u88ab\u5185\u6838IO\u4e8b\u4ef6\u5f02\u6b65\u5524\u9192\u800c\u52a0\u5165Ready\u961f\u5217\u7684\u63cf\u8ff0\u7b26\u96c6\u5408\u5c31\u884c\u4e86\u3002<\/p>\n
\u76ee\u524depell\u662flinux\u5927\u89c4\u6a21\u5e76\u53d1\u7f51\u7edc\u7a0b\u5e8f\u4e2d\u7684\u70ed\u95e8\u9996\u9009\u6a21\u578b\u3002<\/p>\n
epoll\u9664\u4e86\u63d0\u4f9bselect\/poll\u90a3\u79cdIO\u4e8b\u4ef6\u7684\u7535\u5e73\u89e6\u53d1（Level Triggered）\u5916，\u8fd8\u63d0\u4f9b\u4e86\u8fb9\u6cbf\u89e6\u53d1（Edge Triggered），\u8fd9\u5c31\u4f7f\u5f97\u7528\u6237\u7a7a\u95f4\u7a0b\u5e8f\u6709\u53ef\u80fd\u7f13\u5b58IO\u72b6\u6001，\u51cf\u5c11epoll_wait\/epoll_pwait\u7684\u8c03\u7528，\u63d0\u9ad8\u5e94\u7528\u7a0b\u5e8f\u6548\u7387\u3002<\/p>\n
\u53ef\u4ee5\u4f7f\u7528cat\u547d\u4ee4\u67e5\u770b\u4e00\u4e2a\u8fdb\u7a0b\u53ef\u4ee5\u6253\u5f00\u7684socket\u63cf\u8ff0\u7b26\u4e0a\u9650\u3002<\/p>\n
cat \/proc\/sys\/fs\/file-max<\/p>\n
\u5982\u6709\u9700\u8981，\u53ef\u4ee5\u901a\u8fc7\u4fee\u6539\u914d\u7f6e\u6587\u4ef6\u7684\u65b9\u5f0f\u4fee\u6539\u8be5\u4e0a\u9650\u503c\u3002<\/p>\n
sudo vi \/etc\/security\/limits.conf<\/p>\n
\u5728\u6587\u4ef6\u5c3e\u90e8\u5199\u5165\u4ee5\u4e0b\u914d\u7f6e,soft\u8f6f\u9650\u5236，hard\u786c\u9650\u5236\u3002\u5982\u4e0b\u56fe\u6240\u793a\u3002<\/p>\n
* soft nofile 65536<\/p>\n
* hard nofile 100000<\/p>\n
![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/07\/20250729163619-6888f8837b9a6.png\")
<\/p>\n<\/p>\n\u57fa\u7840API<\/h3>\n
1.\u521b\u5efa\u4e00\u4e2aepoll\u53e5\u67c4，\u53c2\u6570size\u7528\u6765\u544a\u8bc9\u5185\u6838\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u4e2a\u6570，\u8ddf\u5185\u5b58\u5927\u5c0f\u6709\u5173\u3002<\/p>\n
#include <sys\/epoll.h><\/p>\n
int epoll_create(int size) size：\u76d1\u542c\u6570\u76ee<\/p>\n
2.\u63a7\u5236\u67d0\u4e2aepoll\u76d1\u63a7\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4e0a\u7684\u4e8b\u4ef6：\u6ce8\u518c\u3001\u4fee\u6539\u3001\u5220\u9664\u3002<\/p>\n
#include <sys\/epoll.h><\/p>\n
int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event)<\/p>\n
epfd： \u4e3aepoll_creat\u7684\u53e5\u67c4<\/p>\n<\/p>\n
op： \u8868\u793a\u52a8\u4f5c，\u75283\u4e2a\u5b8f\u6765\u8868\u793a：<\/p>\n
EPOLL_CTL_ADD (\u6ce8\u518c\u65b0\u7684fd\u5230epfd)，<\/p>\n
EPOLL_CTL_MOD (\u4fee\u6539\u5df2\u7ecf\u6ce8\u518c\u7684fd\u7684\u76d1\u542c\u4e8b\u4ef6)，<\/p>\n
EPOLL_CTL_DEL (\u4eceepfd\u5220\u9664\u4e00\u4e2afd)；<\/p>\n<\/p>\n
event： \u544a\u8bc9\u5185\u6838\u9700\u8981\u76d1\u542c\u7684\u4e8b\u4ef6<\/p>\n<\/p>\n
struct epoll_event {<\/p>\n
__uint32_t events; \/* Epoll events *\/<\/p>\n
epoll_data_t data; \/* User data variable *\/<\/p>\n
};<\/p>\n<\/p>\n
typedef union epoll_data {<\/p>\n
void *ptr;<\/p>\n
int fd;<\/p>\n
uint32_t u32;<\/p>\n
uint64_t u64;<\/p>\n
} epoll_data_t;<\/p>\n<\/p>\n
EPOLLIN ： \u8868\u793a\u5bf9\u5e94\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u53ef\u4ee5\u8bfb（\u5305\u62ec\u5bf9\u7aefSOCKET\u6b63\u5e38\u5173\u95ed）<\/p>\n
EPOLLOUT： \u8868\u793a\u5bf9\u5e94\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u53ef\u4ee5\u5199<\/p>\n
EPOLLPRI： \u8868\u793a\u5bf9\u5e94\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u6709\u7d27\u6025\u7684\u6570\u636e\u53ef\u8bfb（\u8fd9\u91cc\u5e94\u8be5\u8868\u793a\u6709\u5e26\u5916\u6570\u636e\u5230\u6765）<\/p>\n
EPOLLERR： \u8868\u793a\u5bf9\u5e94\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u53d1\u751f\u9519\u8bef<\/p>\n
EPOLLHUP： \u8868\u793a\u5bf9\u5e94\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u88ab\u6302\u65ad；<\/p>\n
EPOLLET： \u5c06EPOLL\u8bbe\u4e3a\u8fb9\u7f18\u89e6\u53d1(Edge Triggered)\u6a21\u5f0f，\u8fd9\u662f\u76f8\u5bf9\u4e8e\u6c34\u5e73\u89e6\u53d1(Level Triggered)\u800c\u8a00\u7684<\/p>\n
EPOLLONESHOT：\u53ea\u76d1\u542c\u4e00\u6b21\u4e8b\u4ef6，\u5f53\u76d1\u542c\u5b8c\u8fd9\u6b21\u4e8b\u4ef6\u4e4b\u540e，\u5982\u679c\u8fd8\u9700\u8981\u7ee7\u7eed\u76d1\u542c\u8fd9\u4e2asocket\u7684\u8bdd，\u9700\u8981\u518d\u6b21\u628a\u8fd9\u4e2asocket\u52a0\u5165\u5230EPOLL\u961f\u5217\u91cc<\/p>\n
3.\u7b49\u5f85\u6240\u76d1\u63a7\u6587\u4ef6\u63cf\u8ff0\u7b26\u4e0a\u6709\u4e8b\u4ef6\u7684\u4ea7\u751f，\u7c7b\u4f3c\u4e8eselect()\u8c03\u7528\u3002<\/p>\n
#include <sys\/epoll.h><\/p>\n
int epoll_wait(int epfd, struct epoll_event *events, int maxevents, int timeout)<\/p>\n
events： \u7528\u6765\u5b58\u5185\u6838\u5f97\u5230\u4e8b\u4ef6\u7684\u96c6\u5408，<\/p>\n
maxevents： \u544a\u4e4b\u5185\u6838\u8fd9\u4e2aevents\u6709\u591a\u5927，\u8fd9\u4e2amaxevents\u7684\u503c\u4e0d\u80fd\u5927\u4e8e\u521b\u5efaepoll_create()\u65f6\u7684size，<\/p>\n
timeout： \u662f\u8d85\u65f6\u65f6\u95f4<\/p>\n
-1： \u963b\u585e<\/p>\n
0： \u7acb\u5373\u8fd4\u56de，\u975e\u963b\u585e<\/p>\n
>0： \u6307\u5b9a\u6beb\u79d2<\/p>\n
\u8fd4\u56de\u503c： \u6210\u529f\u8fd4\u56de\u6709\u591a\u5c11\u6587\u4ef6\u63cf\u8ff0\u7b26\u5c31\u7eea，\u65f6\u95f4\u5230\u65f6\u8fd4\u56de0，\u51fa\u9519\u8fd4\u56de-1<\/p>\n
server<\/h3>\n
\u5904\u7406\u6d41\u7a0b：<\/p>\n
\n1.\u521b\u5efa epoll \u5b9e\u4f8b\u5bf9\u8c61 epoll_create<\/p>\n
2.\u5c06\u7528\u4e8e\u76d1\u542c\u7684\u5957\u63a5\u5b57\u6dfb\u52a0\u5230 epoll \u5b9e\u4f8b\u4e2d epoll_ctl<\/p>\n
3.\u68c0\u6d4b\u6dfb\u52a0\u5230 epoll \u5b9e\u4f8b\u4e2d\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u662f\u5426\u5df2\u5c31\u7eea，\u5e76\u5c06\u8fd9\u4e9b\u5df2\u5c31\u7eea\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u8fdb\u884c\u5904\u7406 epoll_wait<\/p>\n
- \n
- \u5982\u679c\u662f\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26，\u548c\u65b0\u5ba2\u6237\u7aef\u5efa\u7acb\u8fde\u63a5，\u5c06\u5f97\u5230\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u6dfb\u52a0\u5230 epoll \u5b9e\u4f8b\u4e2d<\/li>\n
- \u5982\u679c\u662f\u901a\u4fe1\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26，\u548c\u5bf9\u5e94\u7684\u5ba2\u6237\u7aef\u901a\u4fe1，\u5982\u679c\u8fde\u63a5\u5df2\u65ad\u5f00，\u5c06\u8be5\u6587\u4ef6\u63cf\u8ff0\u7b26\u4ece epoll \u5b9e\u4f8b\u4e2d\u5220\u9664
\n\u00a0<\/li>\n<\/ul>\n#include <stdio.h>
\n#include <fcntl.h>
\n#include "wrap.h"
\n#include <sys\/epoll.h>
\nint main(int argc, char *argv[])
\n{
\n\/\/\u521b\u5efa\u5957\u63a5\u5b57 \u7ed1\u5b9a
\nint lfd = tcp4bind(8000,NULL);
\n\/\/\u76d1\u542c
\nListen(lfd,128);
\n\/\/\u521b\u5efa\u6811
\nint epfd = epoll_create(1);
\n\/\/\u5c06lfd\u4e0a\u6811
\nstruct epoll_event ev,evs[1024];
\nev.data.fd = lfd;
\nev.events = EPOLLIN;
\nepoll_ctl(epfd,EPOLL_CTL_ADD,lfd,&ev);
\n\/\/while\u76d1\u542c
\nwhile(1)
\n{
\nint nready = epoll_wait(epfd,evs,1024,-1);\/\/\u76d1\u542c
\nprintf("epoll wait _________________\\\\n");
\nif(nready <0)
\n{
\nperror("");
\nbreak;
\n}
\nelse if( nready == 0)
\n{
\ncontinue;
\n}
\nelse\/\/\u6709\u6587\u4ef6\u63cf\u8ff0\u7b26\u53d8\u5316
\n{
\nint i = 0;
\nfor( i=0;i<nready;i++)
\n{
\n\/\/\u5224\u65adlfd\u53d8\u5316,\u5e76\u4e14\u662f\u8bfb\u4e8b\u4ef6\u53d8\u5316
\nif(evs[i].data.fd == lfd && evs[i].events & EPOLLIN)
\n{
\nstruct sockaddr_in cliaddr;
\nchar ip[16]="";
\nsocklen_t len = sizeof(cliaddr);
\nint cfd = Accept(lfd,(struct sockaddr *)&cliaddr,&len);\/\/\u63d0\u53d6\u65b0\u7684\u8fde\u63a5<\/p>\nprintf("new client ip=%s port =%d\\\\n",inet_ntop(AF_INET,&cliaddr.sin_addr.s_addr,ip,16)
\n,ntohs(cliaddr.sin_port));
\n\/\/\u8bbe\u7f6ecfd\u4e3a\u975e\u963b\u585e
\nint flags = fcntl(cfd,F_GETFL);\/\/\u83b7\u53d6\u7684cfd\u7684\u6807\u5fd7\u4f4d
\nflags |= O_NONBLOCK;
\nfcntl(cfd,F_SETFL,flags);
\n\/\/\u5c06cfd\u4e0a\u6811
\nev.data.fd =cfd;
\nev.events =EPOLLIN | EPOLLET;\/\/\u8bbe\u7f6e\u4e3a\u8fb9\u6cbf\u89e6\u53d1
\nepoll_ctl(epfd,EPOLL_CTL_ADD,cfd,&ev);<\/p>\n}
\nelse if( evs[i].events & EPOLLIN)\/\/cfd\u53d8\u5316 ,\u800c\u4e14\u662f\u8bfb\u4e8b\u4ef6\u53d8\u5316
\n{
\nwhile(1)
\n{
\nchar buf[4]="";
\n\/\/\u5982\u679c\u8bfb\u4e00\u4e2a\u7f13\u51b2\u533a,\u7f13\u51b2\u533a\u6ca1\u6709\u6570\u636e,\u5982\u679c\u662f\u5e26\u963b\u585e,\u5c31\u963b\u585e\u7b49\u5f85,\u5982\u679c
\n\/\/\u662f\u975e\u963b\u585e,\u8fd4\u56de\u503c\u7b49\u4e8e-1,\u5e76\u4e14\u4f1a\u5c06errno \u503c\u8bbe\u7f6e\u4e3aEAGAIN
\nint n = read(evs[i].data.fd,buf,sizeof(buf));
\nif(n < 0)\/\/\u51fa\u9519,cfd\u4e0b\u6811
\n{
\n\/\/\u5982\u679c\u7f13\u51b2\u533a\u8bfb\u5e72\u51c0\u4e86,\u8fd9\u4e2a\u65f6\u5019\u5e94\u8be5\u8df3\u51fawhile(1)\u5faa\u73af,\u7ee7\u7eed\u76d1\u542c
\nif(errno == EAGAIN)
\n{
\nbreak;<\/p>\n}
\n\/\/\u666e\u901a\u9519\u8bef
\nperror("");
\nclose(evs[i].data.fd);\/\/\u5c06cfd\u5173\u95ed
\nepoll_ctl(epfd,EPOLL_CTL_DEL,evs[i].data.fd,&evs[i]);
\nbreak;
\n}
\nelse if(n == 0)\/\/\u5ba2\u6237\u7aef\u5173\u95ed ,
\n{
\nprintf("client close\\\\n");
\nclose(evs[i].data.fd);\/\/\u5c06cfd\u5173\u95ed
\nepoll_ctl(epfd,EPOLL_CTL_DEL,evs[i].data.fd,&evs[i]);\/\/\u4e0b\u6811
\nbreak;
\n}
\nelse
\n{
\n\/\/printf("%s\\\\n",buf);
\nwrite(STDOUT_FILENO,buf,4);
\nwrite(evs[i].data.fd,buf,n);<\/p>\n}
\n}<\/p>\n}<\/p>\n
}<\/p>\n
}<\/p>\n
}<\/p>\n
return 0;
\n}<\/p>\nclient<\/h3>\n
\u5ba2\u6237\u7aef\u4f7f\u7528：<\/p>\n
nc 127.0.0.1 8000<\/p>\n
\u6a21\u62df\u5ba2\u6237\u7aef\u94fe\u63a5\u670d\u52a1\u5668<\/p>\n","protected":false},"excerpt":{"rendered":"
\u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb869\u6b21\uff0c\u70b9\u8d5e22\u6b21\uff0c\u6536\u85cf24\u6b21\u3002\u591a\u8defIO\u8f6c\u63a5\u670d\u52a1\u5668\u4e5f\u53eb\u505a\u591a\u4efb\u52a1IO\u670d\u52a1\u5668\u3002\u8be5\u7c7b\u670d\u52a1\u5668\u5b9e\u73b0\u7684\u4e3b\u65e8\u601d\u60f3\u662f\uff0c\u4e0d\u518d\u7531\u5e94\u7528\u7a0b\u5e8f\u81ea\u5df1\u76d1\u89c6\u5ba2\u6237\u7aef\u8fde\u63a5\uff0c\u53d6\u800c\u4ee3\u4e4b\u7531\u5185\u6838\u66ff\u5e94\u7528\u7a0b\u5e8f\u76d1\u89c6\u6587\u4ef6\u3002<\/p>\n","protected":false},"author":2,"featured_media":45581,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[58,192,884,100,43],"topic":[],"class_list":{"0":"post-45586","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","6":"hentry","7":"category-server","8":"tag-linux","10":"tag-socket","11":"tag-100","12":"tag-43"},"yoast_head":"\n
\u591a\u8defI\/O\u8f6c\u63a5\u670d\u52a1\u5668\uff08select\u3001poll\u3001epoll\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\/45586.html\" \/>\n<meta property=\"og:locale\" content=\"zh_CN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"\u591a\u8defI\/O\u8f6c\u63a5\u670d\u52a1\u5668\uff08select\u3001poll\u3001epoll\uff09 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"og:description\" content=\"\u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb869\u6b21\uff0c\u70b9\u8d5e22\u6b21\uff0c\u6536\u85cf24\u6b21\u3002\u591a\u8defIO\u8f6c\u63a5\u670d\u52a1\u5668\u4e5f\u53eb\u505a\u591a\u4efb\u52a1IO\u670d\u52a1\u5668\u3002\u8be5\u7c7b\u670d\u52a1\u5668\u5b9e\u73b0\u7684\u4e3b\u65e8\u601d\u60f3\u662f\uff0c\u4e0d\u518d\u7531\u5e94\u7528\u7a0b\u5e8f\u81ea\u5df1\u76d1\u89c6\u5ba2\u6237\u7aef\u8fde\u63a5\uff0c\u53d6\u800c\u4ee3\u4e4b\u7531\u5185\u6838\u66ff\u5e94\u7528\u7a0b\u5e8f\u76d1\u89c6\u6587\u4ef6\u3002\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.wsisp.com\/helps\/45586.html\" \/>\n<meta property=\"og:site_name\" content=\"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"article:published_time\" content=\"2025-07-29T16:36:20+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/07\/20250729163610-6888f87a0de08.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=\"11 \u5206\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/45586.html\",\"url\":\"https:\/\/www.wsisp.com\/helps\/45586.html\",\"name\":\"\u591a\u8defI\/O\u8f6c\u63a5\u670d\u52a1\u5668\uff08select\u3001poll\u3001epoll\uff09 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\",\"isPartOf\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/#website\"},\"datePublished\":\"2025-07-29T16:36:20+00:00\",\"dateModified\":\"2025-07-29T16:36:20+00:00\",\"author\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41\"},\"breadcrumb\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/45586.html#breadcrumb\"},\"inLanguage\":\"zh-Hans\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.wsisp.com\/helps\/45586.html\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/45586.html#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"\u9996\u9875\",\"item\":\"https:\/\/www.wsisp.com\/helps\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"\u591a\u8defI\/O\u8f6c\u63a5\u670d\u52a1\u5668\uff08select\u3001poll\u3001epoll\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":"\u591a\u8defI\/O\u8f6c\u63a5\u670d\u52a1\u5668\uff08select\u3001poll\u3001epoll\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\/45586.html","og_locale":"zh_CN","og_type":"article","og_title":"\u591a\u8defI\/O\u8f6c\u63a5\u670d\u52a1\u5668\uff08select\u3001poll\u3001epoll\uff09 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","og_description":"\u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb869\u6b21\uff0c\u70b9\u8d5e22\u6b21\uff0c\u6536\u85cf24\u6b21\u3002\u591a\u8defIO\u8f6c\u63a5\u670d\u52a1\u5668\u4e5f\u53eb\u505a\u591a\u4efb\u52a1IO\u670d\u52a1\u5668\u3002\u8be5\u7c7b\u670d\u52a1\u5668\u5b9e\u73b0\u7684\u4e3b\u65e8\u601d\u60f3\u662f\uff0c\u4e0d\u518d\u7531\u5e94\u7528\u7a0b\u5e8f\u81ea\u5df1\u76d1\u89c6\u5ba2\u6237\u7aef\u8fde\u63a5\uff0c\u53d6\u800c\u4ee3\u4e4b\u7531\u5185\u6838\u66ff\u5e94\u7528\u7a0b\u5e8f\u76d1\u89c6\u6587\u4ef6\u3002","og_url":"https:\/\/www.wsisp.com\/helps\/45586.html","og_site_name":"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","article_published_time":"2025-07-29T16:36:20+00:00","og_image":[{"url":"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/07\/20250729163610-6888f87a0de08.png"}],"author":"admin","twitter_card":"summary_large_image","twitter_misc":{"\u4f5c\u8005":"admin","\u9884\u8ba1\u9605\u8bfb\u65f6\u95f4":"11 \u5206"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/www.wsisp.com\/helps\/45586.html","url":"https:\/\/www.wsisp.com\/helps\/45586.html","name":"\u591a\u8defI\/O\u8f6c\u63a5\u670d\u52a1\u5668\uff08select\u3001poll\u3001epoll\uff09 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","isPartOf":{"@id":"https:\/\/www.wsisp.com\/helps\/#website"},"datePublished":"2025-07-29T16:36:20+00:00","dateModified":"2025-07-29T16:36:20+00:00","author":{"@id":"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41"},"breadcrumb":{"@id":"https:\/\/www.wsisp.com\/helps\/45586.html#breadcrumb"},"inLanguage":"zh-Hans","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.wsisp.com\/helps\/45586.html"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/www.wsisp.com\/helps\/45586.html#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"\u9996\u9875","item":"https:\/\/www.wsisp.com\/helps"},{"@type":"ListItem","position":2,"name":"\u591a\u8defI\/O\u8f6c\u63a5\u670d\u52a1\u5668\uff08select\u3001poll\u3001epoll\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\/45586","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=45586"}],"version-history":[{"count":0,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/posts\/45586\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/media\/45581"}],"wp:attachment":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/media?parent=45586"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/categories?post=45586"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/tags?post=45586"},{"taxonomy":"topic","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/topic?post=45586"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
- \u200blfd\u00a0\u901a\u5e38\u662f\u8f83\u5c0f\u7684\u503c：
- \u5728\u00a0select\u00a0\u51fd\u6570\u4e2d，rset\u00a0\u662f\u4e00\u4e2a\u00a0fd_set\u00a0\u7c7b\u578b\u7684\u4f4d\u56fe\u96c6\u5408，\u5176\u6838\u5fc3\u4f5c\u7528\u662f\u6807\u8bc6\u9700\u8981\u76d1\u63a7\u7684\u53ef\u8bfb\u6587\u4ef6\u63cf\u8ff0\u7b26（FD）\u96c6\u5408，\u5e76\u5728\u51fd\u6570\u8fd4\u56de\u65f6\u6807\u8bb0\u54ea\u4e9bFD\u5df2\u5c31\u7eea\u53ef\u8bfb\u3002<\/li>\n<\/ul>\n
- \u5728\u00a0select\u00a0\u51fd\u6570\u4e2d，\u5185\u6838\u904d\u5386\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408（rset）\u7684\u65b9\u5f0f\u662f\u901a\u8fc7\u7ebf\u6027\u626b\u63cf\u4f4d\u56fe，\u4ece\u6587\u4ef6\u63cf\u8ff0\u7b26 \u200b0\u200b \u5f00\u59cb，\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u6bd4\u7279\u4f4d\u662f\u5426\u88ab\u7f6e\u4f4d（\u5373\u662f\u5426\u4e3a1），\u76f4\u5230\u8fbe\u5230\u00a0maxfd + 1\u00a0\u6307\u5b9a\u7684\u8303\u56f4\u3002\u4ece0\u5230\u00a0maxfd，\u65e0\u8bba\u6587\u4ef6\u63cf\u8ff0\u7b26\u662f\u5426\u6253\u5f00\u6216\u6d3b\u8dc3\u3002\u8fd9\u79cd\u8bbe\u8ba1\u7b80\u5355\u4f46\u6548\u7387\u4f4e，\u662f\u00a0select\u00a0\u88ab\u00a0epoll\u00a0\u53d6\u4ee3\u7684\u4e3b\u8981\u539f\u56e0\u4e4b\u4e00<\/li>\n<\/ul>\n