#!/usr/bin/python
"""
    Serial to Telnet Proxy
    Creates a proxy between a TCP socket and a serial console.

    Copyright (C) 2009  Justin Lee

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""

import sys, os, socket, signal, string

# defaults
_debug = 0
bind = '127.0.0.1'
port = '2300'

print "Serial to Telnet Proxy  Copyright (C) 2009  Justin Lee"
print "This program comes with ABSOLUTELY NO WARRANTY. This is free software, and you"
print "are welcome to redistribute it under certain conditions. For details, see the"
print "full license at http://www.gnu.org/licenses/gpl-3.0.html"
print ""

def usage():
    print "Usage:", sys.argv[0], "<device>", "[port]"
    print "E.g. :", sys.argv[0], "/dev/cu.PL2303-0000101D"
    print "E.g. :", sys.argv[0], "/dev/cu.PL2303-0000101D", "2300"

def info(s):
    print s
    return

def debug(s):
    if _debug: print "[DEBUG]", s
    return

def proxy(fd, cs):
    # send IAC WILL ECHO
    cs.send("\xFF\xFB\x01")
    # send IAC WILL SUPPRESS_GO_AHEAD
    cs.send("\xFF\xFB\x03")
    # send IAC WON'T LINEMODE
    cs.send("\xFF\xFC\x22")

    # fork process
    debug("Forking process")
    pid = os.fork()

    # child - serial to net
    if pid == 0:
        while 1:
            s = os.read(fd, 4096)
            if not s: break
            for c in s:
                # ignore telnet control characters
                # ignore NULL (fixes cisco bug)
                if ord(c) < 240 and ord(c) > 0:
                    cs.sendall(c)

    # parent - net to serial
    else:
        while 1:
            s = cs.recv(4096)
            if not s: break
            for c in s:
                # ignore telnet control characters
                # ignore NULL (fixes cisco bug)
                if ord(c) < 240 and ord(c) > 0:
                    os.write(fd, c)

        os.kill(pid, signal.SIGKILL)
        os.wait()
        cs.close()

# show usage if there's insufficient args
if len(sys.argv) < 2:
    usage()
    exit(1)

# get input from command line
dev = sys.argv[1]
if len(sys.argv) == 3: port = sys.argv[2]

# open device for read/write
fd = os.open(dev, os.O_RDWR)
debug("Device " + dev + " opened for read/write.")

# create socket to listen
ss = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
ss.bind((bind, int(port)))
ss.listen(1)
info("Listening on " + bind + ":" + port + ".")

# loop and accept incoming connections
while 1:
    debug("Waiting for socket connection")
    cs, ca = ss.accept()
    info("Accepted connection from " + ca[0] + ":" + str(ca[1]) + ".")

    # start proxy
    proxy(fd, cs)
    info("Connection from " + ca[0] + ":" + str(ca[1]) + " closed.")

ss.close()
os.close(fd)