client.py

import sys
import socket

HOST, PORT = "127.0.0.1", 9999
data = " ".join(sys.argv[1:])

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

sock.connect((HOST, PORT))
sock.send(data + "\n")

received = sock.recv(1024)
sock.close()

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

server.py

import SocketServer

class TCPHandler(SocketServer.BaseRequestHandler):
    
    def handle(self):
        self.data = self.request.recv(1024).strip()
        print "%s wrote: " % self.client_address[0]
        print self.data
        
        self.request.send(self.data.upper())

if __name__ == "__main__":
    HOST, PORT = "127.0.0.1", 9999
    
    server = SocketServer.TCPServer((HOST, PORT), TCPHandler)
    
    server.serve_forever()