Простейший клиент и сервер на python (документация)

Сервер:

import SocketServer

class MyTCPHandler(SocketServer.BaseRequestHandler):
"""
The RequestHandler class for our server.

It is instantiated once per connection to the server, and must
override the handle() method to implement communication to the
client.
"""

def handle(self):
# self.request is the TCP socket connected to the client
self.data = self.request.recv(1024).strip()
print "%s wrote:" % self.client_address[0]
print self.data
# just send back the same data, but upper-cased
self.request.send(self.data.upper())

if __name__ == "__main__":
HOST, PORT = "localhost", 9999

# Create the server, binding to localhost on port 9999
server = SocketServer.TCPServer((HOST, PORT), MyTCPHandler)

# Activate the server; this will keep running until you
# interrupt the program with Ctrl-C
server.serve_forever()

Клиент:

import socket
import sys

HOST, PORT = "localhost", 9999
data = " ".join(sys.argv[1:])

# Create a socket (SOCK_STREAM means a TCP socket)
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# Connect to server and send data
sock.connect((HOST, PORT))
sock.send(data + "\n")

# Receive data from the server and shut down
received = sock.recv(1024)
sock.close()

print "Sent: %s" % data
print "Received: %s" % received

Соответственно расстарляем табуляцию.