We use a test_socketpair() function to wrap a few lines that test the socket's socketpair() function.

List 3.8 shows an example of socketpair, as follows:

#!/usr/bin/env python 
# Python Network Programming Cookbook, Second Edition -- Chapter - 3 
# 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. 
# Follow the comments inline to make the program work with Python 2. 
 
import socket 
import os 
 
BUFSIZE = 1024 
 
def test_socketpair(): 
    """ Test Unix socketpair""" 
    parent, child = socket.socketpair() 
     
    pid = os.fork() 
    try: 
        if pid: 
            print ("@Parent, sending message...") 
            child.close() 
 
            parent.sendall(bytes("Hello from parent!", 'utf-8')) 
            # Comment out the above line and uncomment 
              the below line for Python 2.7. 
            # parent.sendall("Hello from parent!") 
 
            response = parent.recv(BUFSIZE) 
            print ("Response from child:", response) 
            parent.close() 
         
        else: 
            print ("@Child, waiting for message from parent") 
            parent.close() 
            message = child.recv(BUFSIZE) 
            print ("Message from parent:", message) 
 
            child.sendall(bytes("Hello from child!!", 'utf-8')) 
            # Comment out the above line and 
              uncomment the below line for Python 2.7. 
            # child.sendall("Hello from child!!") 
 
            child.close() 
    except Exception as err: 
        print ("Error: %s" %err) 
 
 
if __name__ == '__main__': 
    test_socketpair() 
 

The output from the preceding script is as follows:

$ python 3_8_ipc_using_socketpairs.py
@Parent, sending message...
@Child, waiting for message from parent
Message from parent: b'Hello from parent!'
Response from child: b'Hello from child!!'