Learning Python Network Programming

Chapter 8

An eventlet-based chat server

The eventlet library provides a high-level API for event-driven programming, but
it does so in a style that mimics the procedural, blocking-IO style that we used in our
multithreaded servers. The upshot is that we can effectively take our multithreaded
chat server code, make a few minor modifications to it to use eventlet instead,
and immediately gain the benefits of the event-driven model!

The eventlet library is available in PyPi, and it can be installed with pip,
as shown here:

$ pip install eventlet

Downloading/unpacking eventlet

The eventlet library automatically falls back to select if poll is not

available, so it will run properly on Windows.

Once it's installed, create a new file called 4.1-chat_server-eventlet.py and save
the following code in it:

import eventlet

import eventlet.queue as queue

import tincanchat

HOST = tincanchat.HOST

PORT = tincanchat.PORT

send_queues = {}

def handle_client_recv(sock, addr):

""" Receive messages from client and broadcast them to

other clients until client disconnects """

rest = bytes()

while True:

try:

(msgs, rest) = tincanchat.recv_msgs(sock)

except (EOFError, ConnectionError):

handle_disconnect(sock, addr)

break

for msg in msgs:

msg = '{}: {}'.format(addr, msg)

print(msg)

broadcast_msg(msg)