Michael Kerrisk : "The Linux Programming Interface" CH.44 : sequence number server(Python Implementation)

client.py

# Michael Kerrisk : "The Linux Programming Interface" CH.44 : sequence number server(Python Implementation)
# fifo_seqnum_client

import atexit
import os
import struct
import sys

import config

pid = os.getpid()
CLIENT_FIFO = config.CLIENT_FIFO_TEMPLATE % pid

@atexit.register
def remove_fifo():
    os.remove(CLIENT_FIFO)

def main():
    os.mkfifo(CLIENT_FIFO)

    seq_len = int(sys.argv[1]) if len(sys.argv) > 1 else 1

    # print 'client', pid, seq_len

    # Construct request message, open server FIFO, and send message
    wr_fd = os.open(config.SERVER_FIFO, os.O_WRONLY)
    os.write(wr_fd, struct.pack(config.CLIENT_FORMAT, pid, seq_len))
    os.close(wr_fd)

    # Open our FIFO, read and display response
    rd_fd = os.open(CLIENT_FIFO, os.O_RDONLY)
    resp = os.read(rd_fd, config.SERVER_SIZE)
    os.close(rd_fd)

    print struct.unpack(config.SERVER_FORMAT, resp)

if __name__ == '__main__':
    main()

config.py

# Michael Kerrisk : "The Linux Programming Interface" CH.44 : sequence number server(Python Implementation)
# fifo_seqnum_config

import struct

CLIENT_FORMAT = 'II'
CLIENT_SIZE = struct.calcsize(CLIENT_FORMAT)

SERVER_FORMAT = 'I'
SERVER_SIZE = struct.calcsize(SERVER_FORMAT)

SERVER_FIFO = 'seqnum_sv'
CLIENT_FIFO_TEMPLATE = 'seqnum_cl.%ld'

server.py

# Michael Kerrisk : "The Linux Programming Interface" CH.44 : sequence number server(Python Implementation)
# fifo_seqnum_server

import  os
import struct

import config

def remove_fifo(signum, frame):
    os.remove(config.SERVER_FIFO)

def main():
    seq_num = 0

    while True:
        # Open client FIFO (previously created by client)
        rd_fd = os.open(config.SERVER_FIFO, os.O_RDONLY)
        req = os.read(rd_fd, config.CLIENT_SIZE)
        os.close(rd_fd)

        (pid, seq_len) = struct.unpack(config.CLIENT_FORMAT, req)
        print 'server', pid, seq_len

        # Send response and close FIFO
        wr_fd = os.open(config.CLIENT_FIFO_TEMPLATE % pid, os.O_WRONLY)
        os.write(wr_fd, struct.pack(config.SERVER_FORMAT, seq_num))
        os.close(wr_fd)

        seq_num += seq_len

if __name__ == '__main__':
    main()