netconsole.py

#!/usr/bin/env python

# Copyright (c) Robert Blair Mason Jr. (rbmj) rbmj@verizon.net
# see LICENSE for license information.

import socket
import sys
import threading
import atexit
import time
import os

#allow import in both python 2.x and 3.x
try:
	from Queue import Queue, Empty
except ImportError:
	from queue import Queue, Empty

#ports
UDP_IN_PORT=6666
UDP_OUT_PORT=6668

#set up recieving socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind( ('',UDP_IN_PORT) )

#set up sending socket - use separate socket to avoid race condition
out = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
out.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
out.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
out.bind( ('',UDP_OUT_PORT) ) #bind is necessary for escoteric reasons stated on interwebs

#set up atexit handler to close sockets
def atexit_func():
	sock.close()
	out.close()

atexit.register(atexit_func)

#set up threads to emulate non-blocking io
#thread-level emulation required for compatibility with windows
stdin_queue = Queue()
sock_queue = Queue()

def enqueue_output_file(f, q):
	for line in iter(f.readline, b''): #thanks to stackoverflow
		q.put(line)

def enqueue_output_sock(s, q):
	while True:
		q.put(s.recv(4096))

stdin_reader = threading.Thread(target = enqueue_output_file, args = (sys.stdin, stdin_queue))
sock_reader = threading.Thread(target = enqueue_output_sock, args = (sock, sock_queue))
stdin_reader.daemon = True
sock_reader.daemon = True
stdin_reader.start()
sock_reader.start()

#send a message out the socket
def send_msg(msg):
	out.sendto(line, ('255.255.255.255', UDP_OUT_PORT))

#main loop
have_now=''

group=[]

try:
  while True:
	try: msg = sock_queue.get_nowait()
	except Empty:
		pass # no output
	else:
		sp=msg.split('\n')
		assert len(sp)
		sp[0]=have_now+sp[0]
		have_now=sp[-1]
		sp=sp[:-1]

		for elem in sp:
			if 'Robot_input' in elem:
				os.system('clear')
				for ele in group:
					print ele
				group=[]
			group.append(elem)
		#for i,elem in enumerate(sp):
		#	if 'in:' in elem:
		#		os.system('clear')
		#	sys.stdout.write(elem)
		#	if i+1!=len(sp):
		#		sys.stdout.write('\n')
		#sys.stdout.write(msg)
	try: line = stdin_queue.get_nowait()
	except Empty:
		pass # no input
	else:
		send_msg(line)
	#time.sleep(0.05)
except:
  for elem in group: print elem