Set connection timeout for Linux connect

In the past, we basically used the non-blocking method (connect_nonb) in UNIX Network Programming to Implement the connect () Timeout. I saw an article on the Internet today, which is very interesting,ReprintedAs follows: When I read the Linux kernel source code, I accidentally found that the connect timeout parameter was consistent with the parameter operated with so_sndtimo: 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} This means that on the Linux platform, you can set so_sndtimo before connect to control connection timeout. Write a test code: #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; }