As seen in the previous socket server based on ForkingMixIn, ThreadingMixIn socket server will follow the same coding pattern of an echo server except for a few things. First, our ThreadedTCPServer will inherit from TCPServer and TheadingMixIn. This multi-threaded version will launch a new thread when a client connects to it. Some more details can be found at http://docs.python.org/2/library/socketserver.html.

The request handler class of our socket server, ForkingServerRequestHandler, sends the echo back to the client from a new thread. You can check the thread information here. For the sake of simplicity, we put the client code in a function instead of a class. The client code creates the client socket and sends the message to the server.

Listing 2.2 shows a sample code on the echo socket server using ThreadingMixIn as follows:

#!/usr/bin/env python 
# Python Network Programming Cookbook, Second Edition -- Chapter - 2 
# This program is optimized for Python 3.5.2. 
# It may run on any other version with/without modifications. 
# To make it run on Python 2.7.x, needs some changes due to API differences. 
# begin with replacing "socketserver" with "SocketServer" throughout the program. 
# See more: http://docs.python.org/2/library/socketserver.html 
# See more: http://docs.python.org/3/library/socketserver.html 
 
import os 
import socket 
import threading 
import socketserver 
 
SERVER_HOST = 'localhost' 
SERVER_PORT = 0 # tells the kernel to pickup a port dynamically 
BUF_SIZE = 1024 
 
 
def client(ip, port, message): 
    """ A client to test threading mixin server"""     
    # Connect to the server 
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 
    sock.connect((ip, port)) 
    try: 
        sock.sendall(bytes(message, 'utf-8')) 
        response = sock.recv(BUF_SIZE) 
        print ("Client received: %s" %response) 
    finally: 
        sock.close() 
 
 
class ThreadedTCPRequestHandler(socketserver.BaseRequestHandler): 
    """ An example of threaded TCP request handler """ 
    def handle(self): 
        data = self.request.recv(1024) 
        cur_thread = threading.current_thread() 
        response = "%s: %s" %(cur_thread.name, data) 
        self.request.sendall(bytes(response, 'utf-8')) 
 
class ThreadedTCPServer(socketserver.ThreadingMixIn, socketserver.TCPServer): 
    """Nothing to add here, inherited everything necessary from parents""" 
    pass 
 
 
if __name__ == "__main__": 
    # Run server 
    server = ThreadedTCPServer((SERVER_HOST, SERVER_PORT), 
                                ThreadedTCPRequestHandler) 
    ip, port = server.server_address # retrieve ip address 
 
    # Start a thread with the server -- one  thread per request 
    server_thread = threading.Thread(target=server.serve_forever) 
    # Exit the server thread when the main thread exits 
    server_thread.daemon = True 
    server_thread.start() 
    print ("Server loop running on thread: %s"  %server_thread.name) 
     
    # Run clients 
    client(ip, port, "Hello from client 1") 
    client(ip, port, "Hello from client 2") 
    client(ip, port, "Hello from client 3") 
     
    # Server cleanup 
    server.shutdown()