import socket, string

def do_something(x):
  lst = map(None, x);
  lst.reverse();
  return string.join(lst, "")

HOST = ""                 # localhost
PORT = 33333
srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
srv.bind((HOST, PORT))
while 1:
  print "Слушаю порт 33333"
  srv.listen(1)             
  sock, addr = srv.accept()
  while 1:
    pal = sock.recv(1024)
    if not pal: 
      break
    print "Получено от %s:%s:" % addr, pal
    lap = do_something(pal)
    print "Отправлено %s:%s:" % addr, lap
    sock.send(lap)
  sock.close()

import socket

HOST = ""                 # удаленный компьютер (localhost)
PORT = 33333              # порт на удаленном компьютере
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((HOST, PORT))
sock.send("ПАЛИНДРОМ")
result = sock.recv(1024)
sock.close()
print "Получено:", result

Traceback (most recent call last):
  File "<pyshell#6>", line 1, in <module>
    sock.connect((HOST, PORT))
  File "C:\Python27\lib\socket.py", line 222, in meth
    return getattr(self._sock,name)(*args)
error: [Errno 10049]

HOST = "localhost"