select監聽socket的connect編程實現

//
// Created by xx on 2020/4/10.
//

#include "mySocketConnectTimeOut.h"


int socket_connect_timeout(char *ip, int port){
    int sock_fd;
    struct sockaddr_in server;
    server.sin_family = AF_INET;
    server.sin_port = htons(port);
    server.sin_addr.s_addr = inet_addr(ip);

    if((sock_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
        perror("socket");
        return -1;
    }
    printf("socket create!\n");
    int res = connect(sock_fd, (struct sockaddr *)&server, sizeof(server));
    if(res < 0){
        perror("connect");
        return -1;
    }

    fd_set rset, wset;
    int error;
    socklen_t len;
    FD_ZERO(&rset);
    FD_SET(sock_fd, &rset);
    FD_ZERO(&wset);
    FD_SET(sock_fd, &wset);

    struct timeval interval;
    interval.tv_sec = 5;
    interval.tv_usec = 0;

    int n = select(sock_fd + 1, &rset, &wset, NULL, &interval);
    if(n < 0){
        perror("select");
        return -1;
    }
    if(FD_ISSET(sock_fd, &rset) || FD_ISSET(sock_fd, &wset)){
        len = sizeof(error);
        int flag;
        if((flag = getsockopt(sock_fd, SOL_SOCKET, SO_ERROR, &error, &len)) != 0){
            perror("getsockopt");
            return -1;
        }
    } else{
        printf("connect no response!\n");
        return -1;
    }

    return sock_fd;
}