from multiprocessing import *

latin = str

SENTINEL = latin('')

def _read_until_sentinel(conn):
    recv_list = []
    for msg in iter(conn.recv_bytes, SENTINEL):
        recv_list.append(msg)
        
    return latin('').join(recv_list)
    
def _echo(conn):
    msg = _read_until_sentinel(conn)
    conn.send_bytes(msg)
    conn.send_bytes(SENTINEL)
    conn.close()

def main():
    conn, child_conn = Pipe()

    p = Process(target=_echo, args=(child_conn,))
    p.daemon = True
    p.start()

    really_big_msg = latin('X') * (1024 * 1024 * 128)
    conn.send_bytes(really_big_msg)
    conn.send_bytes(SENTINEL)                          # tell child to quit
    recv = _read_until_sentinel(conn)
    assert recv == really_big_msg

    child_conn.close()

if __name__ == "__main__":
    main()