QTCP服务器没有向clien发送消息

Question

嗨，我已经用pyqt4中的qtcSocket创建了一个tcp服务器。我很容易收到客户的信息。但此服务器无法向客户端发送消息。请告诉我哪里做错了。你知道吗

    def sendMessage(self):

    print('send message is called')
    message = 'OKVTdddddssssddssss'

    reply = QtCore.QByteArray()
    reply.append(message)
    stream = QtCore.QDataStream(reply, QtCore.QIODevice.WriteOnly)
    stream.setVersion(QtCore.QDataStream.Qt_4_0)
    stream.writeUInt16(0)
    stream.writeQString(message)
    stream.device().seek(0)
    stream.writeUInt16(reply.size() - SIZEOF_UINT16)
    self.tcp.write(reply)