Linux IO多路复用之epoll网络编程

前言

本章节是用基本的Linux基本函数加上epoll调用编写一个完整的服务器和客户端例子，可在Linux上运行，客户端和服务端的功能如下:

• 客户端从标准输入读入一行，发送到服务端
• 服务端从网络读取一行，然后输出到客户端
• 客户端收到服务端的响应，输出这一行到标准输出

服务端

代码如下:

#include #include     /* basic system data types */#include    /* basic socket definitions */#include    /* sockaddr_in{} and other Internet defns */#include     /* inet(3) functions */#include  /* epoll function */#include    /* nonblocking */#include  /*setrlimit */#include #include #include #include #define MAXEPOLLSIZE 10000#define MAXLINE 10240int handle(int connfd);int setnonblocking(int sockfd){  if (fcntl(sockfd, F_SETFL, fcntl(sockfd, F_GETFD, 0)|O_NONBLOCK) == -1) {    return -1;  }  return 0;}int main(int argc, char **argv){  int servPort = 6888;  int listenq = 1024;  int listenfd, connfd, kdpfd, nfds, n, nread, curfds,acceptCount = 0;  struct sockaddr_in servaddr, cliaddr;  socklen_t socklen = sizeof(struct sockaddr_in);  struct epoll_event ev;  struct epoll_event events[MAXEPOLLSIZE];  struct rlimit rt;  char buf[MAXLINE];  /* 设置每个进程允许打开的最大文件数 */  rt.rlim_max = rt.rlim_cur = MAXEPOLLSIZE;  if (setrlimit(RLIMIT_NOFILE, &rt) == -1)   {    perror("setrlimit error");    return -1;  }  bzero(&servaddr, sizeof(servaddr));  servaddr.sin_family = AF_INET;   servaddr.sin_addr.s_addr = htonl (INADDR_ANY);  servaddr.sin_port = htons (servPort);  listenfd = socket(AF_INET, SOCK_STREAM, 0);   if (listenfd == -1) {    perror("can't create socket file");    return -1;  }  int opt = 1;  setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));  if (setnonblocking(listenfd) < 0) {    perror("setnonblock error");  }  if (bind(listenfd, (struct sockaddr *) &servaddr, sizeof(struct sockaddr)) == -1)   {    perror("bind error");    return -1;  }   if (listen(listenfd, listenq) == -1)   {    perror("listen error");    return -1;  }  /* 创建 epoll 句柄，把监听 socket 加入到 epoll 集合里 */  kdpfd = epoll_create(MAXEPOLLSIZE);  ev.events = EPOLLIN | EPOLLET;  ev.data.fd = listenfd;  if (epoll_ctl(kdpfd, EPOLL_CTL_ADD, listenfd, &ev) < 0)   {    fprintf(stderr, "epoll set insertion error: fd=%d\n", listenfd);    return -1;  }  curfds = 1;  printf("epollserver startup,port %d, max connection is %d, backlog is %d\n", servPort, MAXEPOLLSIZE, listenq);  for (;;) {    /* 等待有事件发生 */    nfds = epoll_wait(kdpfd, events, curfds, -1);    if (nfds == -1)    {      perror("epoll_wait");      continue;    }    /* 处理所有事件 */    for (n = 0; n < nfds; ++n)    {      if (events[n].data.fd == listenfd)       {        connfd = accept(listenfd, (struct sockaddr *)&cliaddr,&socklen);        if (connfd < 0)         {          perror("accept error");          continue;        }        sprintf(buf, "accept form %s:%d\n", inet_ntoa(cliaddr.sin_addr), cliaddr.sin_port);        printf("%d:%s", ++acceptCount, buf);        if (curfds >= MAXEPOLLSIZE) {          fprintf(stderr, "too many connection, more than %d\n", MAXEPOLLSIZE);          close(connfd);          continue;        }         if (setnonblocking(connfd) < 0) {          perror("setnonblocking error");        }        ev.events = EPOLLIN | EPOLLET;        ev.data.fd = connfd;        if (epoll_ctl(kdpfd, EPOLL_CTL_ADD, connfd, &ev) < 0)        {          fprintf(stderr, "add socket '%d' to epoll failed: %s\n", connfd, strerror(errno));          return -1;        }        curfds++;        continue;      }       // 处理客户端请求      if (handle(events[n].data.fd) < 0) {        epoll_ctl(kdpfd, EPOLL_CTL_DEL, events[n].data.fd,&ev);        curfds--;      }    }  }  close(listenfd);  return 0;}int handle(int connfd) {  int nread;  char buf[MAXLINE];  nread = read(connfd, buf, MAXLINE);//读取客户端socket流  if (nread == 0) {    printf("client close the connection\n");    close(connfd);    return -1;  }   if (nread < 0) {    perror("read error");    close(connfd);    return -1;  }    write(connfd, buf, nread);//响应客户端   return 0;}

编译

编译和启动服务端

gcc epollserver.c -o epollserver./epollserver

总结

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