multicast netcat

mcnc.py

#!/usr/bin/python3

# multicast netcat
# https://newtoypia.blogspot.com/2021/09/netcat.html
# 齊步走！ 用 netcat 同步指揮教室裡的所有電腦 

import argparse, sys, re, readline
from warnings import warn
from subprocess import Popen, PIPE

parser = argparse.ArgumentParser(
    description='multicast netcat',
    formatter_class=argparse.ArgumentDefaultsHelpFormatter)
parser.add_argument('-r', '--remotelist', type=str,
    help='file containing the list of remote hosts')
parser.add_argument('-p', '--port', type=int,
    help='default port for remote hosts whose ports are not specified')
args = parser.parse_args()

host_port = {}
with open(args.remotelist) as hostlist:
    for line in hostlist.readlines():
        if re.match(r'^\s*#', line): continue
        m = re.match(r'^\s*(\S+)(\s+(\d+))?', line)
        if m:
            host_port[m.group(1)] = m.group(3) if m.group(3) else args.port
        else:
            warn('ignoring unrecongnized line\n' + line.rstrip())

print(host_port)
print('=' * 60)

proc_list = []
for host in host_port.keys():
    cmd = ['nc', host, str(host_port[host])]
    proc = Popen( cmd, stdin=PIPE, universal_newlines=True, bufsize=1 )
    proc_list.append({
        'host': host,
        'port': host_port[host],
        'proc': proc
    })

while True:
    line = input('mcnc> ') + '\n'
#for line in sys.stdin:
    if re.match(r'^\s*exit\s*$', line): break
    for p in proc_list:
        try:
            p['proc'].stdin.write(line)
        except BrokenPipeError:
            warn('failed writing to [' + p['host'] + ']')

for p in proc_list:
    p['proc'].stdin.close()
    p['proc'].wait()