public UserClient(TcpClient client)   //UserClient的构造函数
        {
            this._client = client;
            ns = _client.GetStream();
            ns.BeginRead(buffer, 0, buffer.Length, new AsyncCallback(streamReceive),null );
        }
private void streamReceive(IAsyncResult ar)  //回调函数
        {
            int BytesRead;
            byte[] rcv;
            BytesRead =ns.EndRead (ar);
            if(BytesRead !=0)
            {
                rcv=new byte [BytesRead -1];
                for (int i = 0; i < BytesRead; i++)
                {
                    rcv[i] = buffer[i];
                }                        
                ns.BeginRead (buffer ,0,buffer.Length ,new AsyncCallback (streamReceive ),null );
            }
        }
这个程序有什么问题？为什么接收不了呢？