simplest socket server and client - before making socket server threaded and supporting multiple client

client.py

import os
import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from PyQt4 import uic

import socket


class MyWindow(QDialog):

    def __init__(self, parent=None):
        super(MyWindow, self).__init__(parent)
        layout = QVBoxLayout(self)
        button = QPushButton('connect')

        for i in range(5):
            cmd_button = QPushButton('cmd - %s' % i)
            layout.addWidget(cmd_button)
            cmd_button.clicked.connect(lambda _, i=i: self.send_cmd(i))

        layout.addWidget(button)
        self.setLayout(layout)
        self.resize(200, 40)

        button.clicked.connect(self.connect_server)

    def connect_server(self):
        self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.socket.connect(('localhost', 5000))

    def send_cmd(self, i):
        cmd = 'cmd - %s<>' % i
        print 'sending : %s' % cmd
        self.socket.send(cmd)


def main():
    app = QApplication(sys.argv)
    win = MyWindow()
    win.show()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

mysocket.py

# enable ctrl-c to kill the app
import signal
signal.signal(signal.SIGINT, signal.SIG_DFL)

import socket
import threading


class SocketServer(object):

    def __init__(self, port=0):
        self.host = 'localhost'
        self.port = port
        self.bufsize = 4096
        self.backlog = 5
        self.separator = '<>'

    def listen(self):
        while True:
            client, address = self.socket.accept()
            # client.settimeout(60)
            threading.Thread(
                target=self.server, args=(client, address)).start()

    def start(self):
        self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.socket.bind((self.host, self.port))
        self.socket.listen(self.backlog)

        threading.Thread(target=self.listen).start()

    def server(self, client, address):
        data = client.recv(self.bufsize)
        while True:

            if self.separator in data:
                data_split = data.split(self.separator)
                cmds = data_split[:-1]

                # execute cmds in threads
                self.process_cmds(cmds)

                data = data_split[-1]

            data += client.recv(self.bufsize)

    def process_cmds(self, cmds):

        for cmd in cmds:
            print 'executing: %s' % cmd

server.py

import os
import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from PyQt4 import uic

# enable ctrl-c to kill the app
import signal
signal.signal(signal.SIGINT, signal.SIG_DFL)

import mysocket


class MyWindow(QDialog):

    def __init__(self, parent=None):
        super(MyWindow, self).__init__(parent)
        layout = QVBoxLayout(self)
        button = QPushButton('start')
        layout.addWidget(button)
        self.setLayout(layout)
        self.resize(200, 40)

        button.clicked.connect(self.start_server)

    def start_server(self):
        self.socket = mysocket.SocketServer(port=5000)
        self.socket.start()


def main():
    app = QApplication(sys.argv)
    win = MyWindow()
    win.show()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()