#include <assert.h>
#include <sys/fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/devpoll.h>
#include <unistd.h>
#include <netinet/in.h>
#include <netinet/in.h>
#include <netinet/ip.h> 
#include <sys/socket.h>
#include <netinet/tcp.h>

int main()
{
    int fd = -1;
    int ret = 0;
    int error_s = 0;
    struct sockaddr_in serv_addr;
    int delay_time = 3000;
    int len_s = sizeof(int);
    int try = 3;
    
    fd = socket(PF_INET, SOCK_STREAM, 0);
    fcntl(fd, F_SETFL, O_NONBLOCK);
    printf("fd=\"%d\" \n", fd);
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(45678);
    serv_addr.sin_addr.s_addr = inet_addr("10.0.0.5");
    
try_connect_again:

    printf("try_connect_again\n");
    printf("attempt left %d ...\n", try);
    if (!try)
        goto fin;
        
    usleep(2000);
    ret = connect(fd, (struct sockaddr *)&serv_addr, sizeof(struct sockaddr_in));
    printf("connect ret=%d, errno=%d\n", ret, errno);
    
    if (errno == EINPROGRESS)
    {
        do
        {
            struct pollfd fds;

            fds.fd = fd;
            fds.events = POLLIN | POLLOUT;
            ret = poll(&fds, 1, delay_time);
            
            if (ret == -1) //poll error
            {
                goto fin;
            }
        }
        while (!ret);
        
        if (ret)
        {
            ret = getsockopt(fd, SOL_SOCKET, SO_ERROR, &error_s, &len_s);
            printf("getsockopt, ret=%d, error_s=%d \n", ret, error_s);
            if (error_s == 0)
                printf("connected\n");
            else
            {
                try--;
                goto try_connect_again;
            }
        }
        else if (ret == 0)
        {
            try--;
            goto try_connect_again;
        }
    }

fin:
    printf("end\n");
    return 0;
}