Learning Python Network Programming

Client and Server Applications

A multithreaded echo server

A benefit of the multithreading approach is that the OS handles the thread switches
for us, which means we can continue to write our program in a procedural style.
Hence we only need to make small adjustments to our server program to make it
multithreaded, and thus, capable of handling multiple clients simultaneously.

Create a new file called 1.3-echo_server-multi.py and add the following code
to it:

import threading

import tincanchat

HOST = tincanchat.HOST

PORT = tincanchat.PORT

def handle_client(sock, addr):

""" Receive one message and echo it back to client, then close

socket """

try:

msg = tincanchat.recv_msg(sock) # blocks until received

# complete message

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

print(msg)

tincanchat.send_msg(sock, msg) # blocks until sent

except (ConnectionError, BrokenPipeError):

print('Socket error')

finally:

print('Closed connection to {}'.format(addr))

sock.close()

if __name__ == '__main__':

listen_sock = tincanchat.create_listen_socket(HOST, PORT)

addr = listen_sock.getsockname()

print('Listening on {}'.format(addr))

while True:

client_sock,addr = listen_sock.accept()

# Thread will run function handle_client() autonomously

# and concurrently to this while loop

thread = threading.Thread(target=handle_client,

args=[client_sock, addr],

daemon=True)

thread.start()

print('Connection from {}'.format(addr))