TCP Messaging

# -*- coding: utf-8 -*-
"""
Created on Thu Dec 27 15:36:40 2012

@author: narasimhapbl.1863
"""

import sys
import os
from PyQt4 import QtGui
from PyQt4 import QtCore
from PyQt4 import QtNetwork

PORT = 9999
SIZEOF_UINT32 = 4

class Server(QtCore.QObject):

    def __init__(self,HOST):

        super(Server, self).__init__()

        self.tcpServer = QtNetwork.QTcpServer()
        self.tcpServer.listen(QtNetwork.QHostAddress(HOST), PORT)
        self.tcpServer.newConnection.connect(self.addConnection)

    def addConnection(self):

        try:

            self.clientConnection = self.tcpServer.nextPendingConnection()
            self.clientConnection.nextBlockSize = 0

            self.clientConnection.readyRead.connect(self.receiveMessage)
            self.clientConnection.disconnected.connect(self.removeConnection)
            self.clientConnection.error.connect(self.socketError)

        except Exception as ex:

            QtGui.QMessageBox.information(None,"Error", ex.message)

    def receiveMessage(self):

        if self.clientConnection.bytesAvailable() > 0:
            stream = QtCore.QDataStream(self.clientConnection)
            stream.setVersion(QtCore.QDataStream.Qt_4_2)

            if self.clientConnection.nextBlockSize == 0:

                if self.clientConnection.bytesAvailable() < SIZEOF_UINT32:
                    return

                self.clientConnection.nextBlockSize = stream.readUInt32()

            if self.clientConnection.bytesAvailable() < self.clientConnection.nextBlockSize:
                return

            self.Message = stream.readQString()
            self.clientConnection.nextBlockSize = 0
            self.emit(QtCore.SIGNAL('DataReceived'))
            self.clientConnection.nextBlockSize = 0

    def removeConnection(self):
        pass

    def socketError(self):
        pass

class Client(QtGui.QDialog):

    def __init__(self, parent=None):

        super(Client, self).__init__(parent)

        # Ititialize socket
        self.Clientsocket = QtNetwork.QTcpSocket()

        # Initialize data IO variables
        self.nextBlockSize = 0
        self.request = None

        self.Clientsocket.disconnected.connect(self.serverHasStopped)
        self.connect(self.Clientsocket,
                     QtCore.SIGNAL("error(QAbstractSocket::SocketError)"),
                     self.serverHasError)

        self.browser = QtGui.QTextBrowser()
        self.lineedit = QtGui.QLineEdit("Message to send")
        self.lineedit.selectAll()
        self.targetSystem = QtGui.QLineEdit("Enter target system")
        self.layout = QtGui.QVBoxLayout(self)#.win)
        self.layout.addWidget(self.browser)
        self.layout.addWidget(self.lineedit)
        self.layout.addWidget(self.targetSystem)

        self.lineedit.setFocus()

        self.lineedit.returnPressed.connect(self.SendData)
        self.setWindowTitle("Client")

    def SendData(self):

        TargetSystems = self.targetSystem.text().split(',')
        Msg2Send = self.lineedit.text()

        for TargetSystem in TargetSystems:

            self.Clientsocket.connectToHost(TargetSystem, PORT)
            self.Clientsocket.waitForConnected(-1)
            self.request = QtCore.QByteArray()
            stream = QtCore.QDataStream(self.request, QtCore.QIODevice.WriteOnly)
            stream.setVersion(QtCore.QDataStream.Qt_4_2)
            stream.writeUInt32(0)
            stream.writeQString(Msg2Send)
            stream.device().seek(0)
            stream.writeUInt32(self.request.size() - SIZEOF_UINT32)
            self.Clientsocket.write(self.request)
            self.nextBlockSize = 0
            self.request = None
#            self.Clientsocket.close()
        self.Clientsocket.disconnectFromHost()


    def serverHasStopped(self):

        self.Clientsocket.close()

    def serverHasError(self):
        self.ServerError = self.Clientsocket.errorString()
        self.emit(QtCore.SIGNAL('SocketError'))
        self.Clientsocket.close()

def ShowMessage():

    QtGui.QMessageBox.information(None,"Message", server.Message)

app = QtGui.QApplication(sys.argv)
print os.getenv('computername')
server = Server(os.getenv('computername'))
client = Client()

QtCore.QObject.connect(server,QtCore.SIGNAL("DataReceived"), ShowMessage)

client.show()
app.exec_()