setsockopt如何设置连接超时

setsockopt函数可以用来设置套接字选项，包括超时时间。下面是一个示例代码，演示如何使用setsockopt函数设置连接超时时间为5秒：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <errno.h>

int main(int argc, char *argv[]) {
    int sockfd;
    struct sockaddr_in servaddr;
    char *ip = "127.0.0.1";
    int port = 8080;

    sockfd = socket(AF_INET, SOCK_STREAM,0);
    if (sockfd < 0) {
        perror("socket error");
        exit(1);
    }

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;    servaddr.sin_port = htons(port);
    if (inet_pton(AF_INET, ip, &servaddr.sin_addr) <= 0) {
        printf("[%s:%d] is not a valid IPaddress\n", ip, port);
        exit(1);
    }

    struct timeval timeout;
    timeout.tv_sec = 5; // 设置超时时间为5秒
    timeout.tv_usec = 0;
    if (setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO, &timeout, sizeof(timeout)) < 0) {
        perror("setsockopt error");
        exit(1);
    }

    if (connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0) {
        if (errno == EINPROGRESS) {
            printf("connecting timeout\n");
            exit(1);
        }
        perror("connect error");
        exit(1);
    }

    printf("connect success\n");
    close(sockfd);
    return 0;
}