Inter process communication using named pipes.

inter_process_communication_using_pipes.py

import time
import os, stat
import numpy as np
from multiprocessing import Process

pipename = 'myfifo'
if not stat.S_ISFIFO(os.stat(pipename).st_mode):
    os.mkfifo(pipename)

def worker(pipe_name):
    pipe_out = os.open(pipe_name, os.O_NONBLOCK|os.O_WRONLY) 
    pipe = os.fdopen(pipe_out, 'wb', buffering=0, closefd=False)

    def write_message(message):
        length = '{0:04d}'.format(len(message))
        pipe.write(b'X')
        pipe.write(length.encode('utf-8'))
        pipe.write(message.encode('utf-8'))

    count = 0
    temp = np.zeros(6)
    while True:
        count += 1
        temp[-1] = count
        write_message(np.array2string(temp))
        time.sleep(0.1)


pipe_in = os.open(pipename, os.O_NONBLOCK|os.O_RDONLY)
pipe = os.fdopen(pipe_in, 'rb', buffering=0)

proc = Process(target=worker, args=(pipename,))
proc.start()

while True:
    # Wait for the message identifier
    in_data = pipe.read(1)
    if in_data == b'X':
        #length of the message 
        raw_length = pipe.read(4)
        message = pipe.read(int(raw_length))
        # Read the message 
        print(np.array(message.decode('utf-8')))
    elif in_data:
        #If the byte read isn't an identifier, something is wrong
        raise Exception('Something wrong!') 
    else:
        time.sleep(0.1)

proc.join()