Inter-process communication using datagram sockets (i.e. UDP).

udp.py

import os
import socket

# `fork` current process. The child's PID is returned to the parent and `0` is
# returned to the child.
pid = os.fork()

# Create a socket. `AF_INET` is the address family for IPv4 and `SOCK_DGRAM` is
# a datagram-based protocol (i.e. UDP). Note that the parent process and the
# child process each create their own socket.
udp = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# `gethostname` returns the current host name.
address = (socket.gethostname(), 5000)

if pid == 0:
    # The child process encodes the user input into `<class 'bytes'>` and sends
    # it to `address`.
    udp.sendto(input().encode(), address)
else:
    # The parent process binds `address` so it can receive data sent to it.
    udp.bind(address)

    # Receive data from the socket. Note that `socket.socket.recv` by default
    # blocks, so the parent waits until the user has finished entering the
    # input.
    print(udp.recv(4096).decode())

udp.close()