Learning Python Network Programming

Chapter 8

A simple echo server

As we work through this chapter, we'll find ourselves reusing several pieces of code,
so to save ourselves from repetition, we'll set up a module with useful functions
that we can reuse as we go along. Create a file called tincanchat.py and save the
following code in it:

import socket

HOST = ''

PORT = 4040

def create_listen_socket(host, port):

""" Setup the sockets our server will receive connection

requests on """

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

sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

sock.bind((host, port))

sock.listen(100)

return sock

def recv_msg(sock):

""" Wait for data to arrive on the socket, then parse into

messages using b'\0' as message delimiter """

data = bytearray()

msg = ''

# Repeatedly read 4096 bytes off the socket, storing the bytes

# in data until we see a delimiter

while not msg:

recvd = sock.recv(4096)

if not recvd:

# Socket has been closed prematurely

raise ConnectionError()

data = data + recvd

if b'\0' in recvd:

# we know from our protocol rules that we only send

# one message per connection, so b'\0' will always be

# the last character

msg = data.rstrip(b'\0')

msg = msg.decode('utf-8')

return msg