在这里EndReceive前后端都需要做判断，不然前端会报错 

static void ReceiveCallback(IAsyncResult ar)
{

    try
    {

        Socket pocket = (Socket)ar.AsyncState;
        int num = pocket.EndReceive(ar);
        if (num <= 0)
        {
            Console.WriteLine("接收到的数据数量：" + num );
        }
        else {
            string msg = Encoding.UTF8.GetString(msgBuff);
            Console.WriteLine("接收到的数据：" + msg);
            Receive(pocket, ReceiveCallback);
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine("接收数据失败！ 异常 ：" + ex.ToString());
    }
}