My application need two (python) methods to send and receive messages(arrays). I am trying to achieve this by using a pipe. I have forked two processes. I observe that if (process == 0), I can either send or receive message from one end (Please correct me if I am wrong). I want both ends of the pipe to be able to send and receive messages to each other. I am new to pipe and fork in python (and to the concept in general) and hence I am finding difficulty in identifying problem with my code. Do i have to use two pipes in order to achieve my goal?

This is the code I am trying to implement:

start, end = os.pipe()

def communication():
    process1 = os.fork()

    if process1:
        r = os.fdopen(start, 'w')
        parent_writes = [1,2,3,4]
        data = json.dumps(parent_writes)
        r.write(data)
        print("Parent writes = ", data)
    else:
        childRead = os.fdopen(end)
        data = childRead.read()
        print("Child reads =", data)

    process2 = os.fork()
    if process2:
        os.close(start)
        w = os.fdopen(end, 'w')
        child_writes = [6, 7, 8, 9]
        data = json.dumps(child_writes)
        w.write(data)
        print("Child writes = ", data)
    else:
        os.close(end)
        parentRead = os.fdopen(start)
        arr = parentRead.read()
        print("Parent reads =", arr)

communication()

This is my output and error message:

Parent writes =  [1, 2, 3, 4]
Child writes =  [6, 7, 8, 9]
Parent reads = [6, 7, 8, 9]
Traceback (most recent call last):
File "/Users/ssss/PycharmProjects/tttt/forkAndPipe.py", line 35, in 
<module>communication()
File "/Users/ssss/PycharmProjects/tttt/forkAndPipe.py", line 17, in 
communication
data = childRead.read()
OSError: [Errno 9] Bad file descriptor

Process finished with exit code 0

Unless I am mistaken, "Bad file descriptor" has got something to do with the way I am forking or closing ends of the pipe inappropriately.

Any help would be greatly appreciated.