C socket udp方式发数据

#define HOST_SERVER_IP "192.168.3.35"
#define HOST_PORT       9501
#define SLEEP_TIME       1
#define LOOP_TIME       3
#define DATA_SIZE       80

int judge_socket_exist()
{
    int        loop_time = 0;
    fd_set     send_data_flag;
    static int socket_fd = -1;

    while(1)
    {
        if (socket_fd <= 0)
        {
            socket_fd = socket(AF_INET, SOCK_DGRAM, 0);
            loop_time++;
        }

        if (socket_fd > 0)
        {
            FD_ZERO(&send_data_flag);
            FD_SET(socket_fd, &send_data_flag);
            FD_SET(0, &send_data_flag);

            //check socket is effective
            if (select(socket_fd+1, NULL, &send_data_flag, NULL, 0) > 0)
            {
                break;
            }
            else
            {
                socket_fd = socket(AF_INET, SOCK_DGRAM, 0);
                loop_time++;
            }
        }

        if (loop_time > LOOP_TIME)
        {
            return -1;
        }

        sleep(SLEEP_TIME);
    }

    return socket_fd;
}

int gsh_post_client(const char* sn, const char* ip)
{
    if (NULL == sn || NULL == ip)
    {
        return -1;
    }

    int    loop_time                     = 0;                      //loop time of fail execute
    int    send_data_length              = 0;                      //length of sending data
    int    select_err                    = -1;                     //flag of select function back value
    int    socket_fd                     = judge_socket_exist();   //set socket flag, socket not close
    struct timeval select_wait           = {1, 0};                 //select function wait time
    char   text[BUFSIZ];
    char   send_data_buffer[DATA_SIZE];                            //buffer of sending data
    struct sockaddr_in socket_addr;                                //socket address of server ip and port
    fd_set send_data_flag;                                         //select function send data flag

    if (socket_fd <= 0)
    {
        fprintf(stderr, "establish socket fail");
        return -1;
    }


    //initialize socket data
    bzero(&socket_addr, sizeof(socket_addr));
    socket_addr.sin_family = AF_INET;
    socket_addr.sin_port   = htons(HOST_PORT);
    inet_aton(HOST_SERVER_IP, &socket_addr.sin_addr);


    //initialize request data
    memset(&send_data_buffer, 0, sizeof(send_data_buffer));
    strcat(send_data_buffer, "sn=");
    strcat(send_data_buffer, sn);
    strcat(send_data_buffer, "&ip=");
    strcat(send_data_buffer, ip);


    while(1)                                      //for no-blocking
    {
        if (loop_time > LOOP_TIME)
        {
            fprintf(stderr, "send data fail\n");
            return -1;
        }

        FD_ZERO(&send_data_flag);
        FD_SET(socket_fd, &send_data_flag);
        FD_SET(0, &send_data_flag);

        select_err = select(socket_fd+1, NULL, &send_data_flag, NULL, &select_wait);

        if (select_err <= 0)
        {
            loop_time++;
        }
        else
        {
            if (FD_ISSET(socket_fd, &send_data_flag))
            {
                loop_time = 0;
                FD_CLR(socket_fd, &send_data_flag);

                while(send_data_length < strlen(send_data_buffer))
                {
                    send_data_length = sendto(socket_fd, send_data_buffer, strlen(send_data_buffer), 0, (struct sockaddr *)&socket_addr, sizeof(socket_addr));

                    if (send_data_length <= 0)
                    {
                        fprintf(stderr, "sending data fail\n");
                        return -1;
                    }

                    if (loop_time > LOOP_TIME)
                    {
                        fprintf(stderr, "length of sending data shorten than data\n");
                        return -1;
                    }

                    if (send_data_length < strlen(send_data_buffer))
                    {
                        loop_time++;
                        sleep(SLEEP_TIME);
                    }
                }

                recvfrom(socket_fd,text,sizeof(text), 0 , NULL, NULL);
                printf("%s", text);

                break;
            }
            else
            {
                loop_time++;
            }
        }

        sleep(SLEEP_TIME);
    }

    return 0;
}