#
# thtp.py
# I0 TCP<->UDP bridge
#
# Neil Gershenfeld  CBA  MIT  11/27/05
# (c) Massachusetts Institute of Technology 2005
# Permission granted for experimental and personal use;
# license for commercial use available from MIT

from socket import *
from string import *
import serial

PORT = 4096

END = 192
ESC = 219
ESC_END = 220
ESC_ESC = 221

TOTAL_LENGTH = 3
SOURCE_ADDRESS = 15
DESTINATION_ADDRESS = 19
SOURCE_PORT = 21
DESTINATION_PORT = 23
DATA = 28

#ser = serial.Serial(port='/dev/usb/ttyUSB0', baudrate=9600)
#ser = serial.Serial(port='COM1', baudrate=9600)
ser = serial.Serial(port='/dev/ttyS0', baudrate=9600)

sock = socket(AF_INET, SOCK_STREAM)
sock.bind(("", PORT))
sock.listen(1)
source_address = gethostbyname("localhost")
print "listening on port",PORT

while 1:
   #
   # wait for an incoming TCP connection
   #
   (client_socket, client_address) = sock.accept()
   data = client_socket.recv(1000)
   #
   # wait for an I0 packet
   #
   count = -1
   length = 10000
   packet = []
   ser.flushInput()
   while 1:
      x = ord(ser.read())
      if (x == END):
         count = -1
         length = 10000
         packet = []
         continue
      if (x == ESC):
         x = ord(ser.read())
         if (x == ESC_END):
            x = END
         elif (x == ESC_ESC):
            x = ESC
         else:
            print "error: unknown ESC"
      packet.append(x)
      count += 1
      if (count == TOTAL_LENGTH):
         length = 256*packet[count-1] + packet[count]
      elif (count == SOURCE_ADDRESS):
         source_address = "%d.%d.%d.%d"%\
            (packet[count-3],packet[count-2],packet[count-1],packet[count])
      elif (count == DESTINATION_ADDRESS):
         destination_address = "%d.%d.%d.%d"%\
            (packet[count-3],packet[count-2],packet[count-1],packet[count])
         #destination_address = "127.0.0.1"
      elif (count == SOURCE_PORT):
         source_port = 256*packet[count-1] + packet[count]
      elif (count == DESTINATION_PORT):
         destination_port = 256*packet[count-1] + packet[count]
      elif (count == length-1):
         data = join(map(chr,packet[DATA:count+1]),sep="")
         print 'received packet from %s to address %s port %d'%\
            (source_address,destination_address,destination_port)
	 break
      elif (count > length):
         print "error: count > length"
   #
   # send the I0 packet on the TCP socket
   #
   client_socket.send("%s"%data)
   client_socket.close()