linux connect 设置连接超时

原来我们实现connect()超时基本上都使用unix网络编程一书的非阻塞方式（connect_nonb），今天在网上看到一篇文章，觉得很有意思，转载如下： 读Linux内核源码的时候偶然发现其connect的超时参数竟然和用SO_SNDTIMO操作的参数一致: 　　File: net/ipv4/af_inet.c     559       timeo = sock_sndtimeo(sk, flags & O_NONBLOCK);     560     561       if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {     562           /* Error code is set above */     563           if (!timeo || !inet_wait_for_connect(sk, timeo))     564               goto out;     565     566           err = sock_intr_errno(timeo);     567           if (signal_pending(current))     568               goto out;     569       } 　　这意味着： 在Linux平台下，可以通过在connect之前设置SO_SNDTIMO来达到控制连接超时的目的。简单的写了份测试代码: #include <stdlib.h> #include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <errno.h> int main(int argc, char *argv[]) {         int fd;         struct sockaddr_in addr;         struct timeval timeo = {3, 0};         socklen_t len = sizeof(timeo);          fd = socket(AF_INET, SOCK_STREAM, 0);         if (argc == 4)                  timeo.tv_sec = atoi(argv[3]);         setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &timeo, len);          addr.sin_family = AF_INET;          addr.sin_addr.s_addr = inet_addr(argv[1]);          addr.sin_port = htons(atoi(argv[2]));         if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) == -1) {                 if (errno == EINPROGRESS) {                         fprintf(stderr, "timeout/n");                         return -1;                 }                 perror("connect");                 return 0;         }         printf("connected/n");         return 0; }