Example of using gevent for async socket server and client

async-socket.py

import gevent
import gevent.server
import gevent.monkey
gevent.monkey.patch_all()

import socket
import string
import random
import filecmp
import os

"""
Example output:

$ python async-socket.py
new connection by ('127.0.0.1', 58020)
client got data!
client got data!
client data matches server
...forever

"""


HOST = ''
PORT = 42000


def server_handler(connection, address):
    print 'new connection by', address
    chunk_size = 1024 * 1024  # how many bytes to send
    data_stream = data_stream_gen()
    while True:
        chunk = str.join('', (next(data_stream) for i in xrange(chunk_size)))
        connection.sendall(chunk)
        with open('server.txt', 'w') as log:
            log.write(chunk)


def data_stream_gen():
    while True:
        yield random.choice(string.ascii_lowercase)


def client():
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.connect((HOST, PORT))
    chunk_size = 512 * 1024  # how many bytes we want to process each loop
    while True:
        data = ''
        while len(data) < chunk_size:
            data += s.recv(chunk_size - len(data))
        if not data:
            break
        # simulate heavy processing
        print 'client got data!'
        gevent.sleep(5)
        with open('client.txt', 'a') as log:
            log.write(data)
        compare_data()
    s.close()


def compare_data():
    if os.stat('client.txt').st_size >= 1024 * 1024:
        if filecmp.cmp('client.txt', 'server.txt', shallow=False):
            print 'client data matches server'
        else:
            print 'error between client and server data'
        with open('client.txt', 'w') as out:
            out.truncate()


if __name__ == '__main__':
    # clear logs
    with open('client.txt', 'w') as out:
        out.truncate()
    with open('server.txt', 'w') as out:
        out.truncate()
    # start server
    server = gevent.server.StreamServer((HOST, PORT), server_handler)
    server.start()
    # start client and wait
    c = gevent.spawn(client).join()