socket编程 ------ UDP服务器

void vLANcommunication( void *pvParameters )
{
    int32    listenfd;

    do{
        listenfd = socket(AF_INET, SOCK_DGRAM, 0);
        if(listenfd    ==    -1)
        {
            debug("ESP8266 UDP server task > socket error\n");
            vTaskDelay(1000/portTICK_RATE_MS);
        }
    }while(listenfd    ==    -1);
    debug("---------------UDP server task > socket ok\n");
    
    

    struct    sockaddr_in    server_addr;
    memset(&server_addr, 0, sizeof(server_addr));/*    Zero out structure */
    server_addr.sin_family    = AF_INET;    /*    Internet address family，AF_INET表示IPv4*/
    server_addr.sin_addr.s_addr    = INADDR_ANY;
    server_addr.sin_len    = sizeof(server_addr);
    server_addr.sin_port = htons(6666);    /* Local port */
    int32 ret;
    do{
        ret    = bind(listenfd, (struct sockaddr *)&server_addr, sizeof(server_addr));
        if    (ret !=    0)    
        {
            debug("ESP8266    UDP server task > bind fail: %d\n",ret);
            vTaskDelay(1000/portTICK_RATE_MS);
        }
    }while(ret != 0);
    debug("---------------UDP server task > bind ok\n");
    
    
    u8 *recv_buf = (u8 *)zalloc(128 * sizeof(u8));
    int32 len = sizeof(struct sockaddr_in);
    struct    sockaddr_in    remote_addr;
    int32 recbytes;
    u16 i;
    u8 tmp_index;
    u8 udp_RxBuf[50];//单条命令不能超过50字节
    u8 udp_RxBuf_index = 0;
    u8 udp_package_length;
    u16 cmd;
    for(;;)
    {  //缓存的数据需要一次性读出来，否则余下的数据读取不到
        recbytes = recvfrom(listenfd, recv_buf, 128, 0, (struct sockaddr *)&remote_addr, (socklen_t *)&len);
sendto(listenfd, recv_buf, recbytes, 0, (struct sockaddr *)&remote_addr, len);// debug("receive a UDP package\n");
    }
}