I have a program which is a udp socket client. I can determine an IP adress to which this program should send. Unfortunately, I configured the computer as Access Point and don't know the address of the UDP server on the other site (I mean I know, but the Access Point doesn't). What, I had in mind is to catch the message and send it to all possible IPs in the range of the network interface (wlan0). For this I wrote a small python proxy, which also shall illustrate the problem. It seems like the server on the other side even gets a message. However there seems no communication back.
Is there a way to catch and forward udp socket communication between client and server programs? Maybe an already existing program/tool for this? I really have not much administration experience.
# Make this Python 2.7 script compatible to Python 3 standard
from __future__ import print_function
# For remote control
import socket
# For sensor readout
import logging
import threading
# For system specific functions
import sys
import os
import time
import datetime
import fcntl
import struct
# Create a sensor log with date and time
layout = '%(asctime)s - %(levelname)s - %(message)s'
# find suitable place for the log file
logging_dir = "/var/log/"
logging_file = "ardu_proxy.log"
if not os.path.isdir(logging_dir):
logging_dir = "/"
# configure logging
logging.basicConfig(filename=logging_dir+logging_file, level=logging.INFO, format=layout)
# Socket for WiFi data transport
udp_port = 14550
udp_server = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
udp_server.bind(('0.0.0.0', udp_port))
def get_if_address(ifname):
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
return socket.inet_ntoa(fcntl.ioctl(
s.fileno(),
0x8915, # SIOCGIFADDR
struct.pack('256s', ifname[:15])
)[20:24])
def get_ip4_adr(adr):
array = adr.split('.')
str = ""
for i in xrange(0, 3):
str += array[i] + "."
return str
def echo_thr(): # trnm_thr() sends commands to Arduino
udp_msg = None
if_name = "wlan0"
# get local interface address
apif_wlan0 = get_if_address(if_name)
apif_wlan0 = get_ip4_adr(apif_wlan0)
while True:
# receive a message running on local host
udp_msg, udp_client = udp_server.recvfrom(512) # Wait for UDP packet from ground station
logging.debug(udp_msg)
print(udp_msg)
# forward the msg and broadcast it in the complete network :D
for ofs in xrange(1, 254):
adr = apif_wlan0 + str(ofs)
print(adr, ": ", udp_msg)
udp_server.sendto(udp_msg, (adr, udp_port) )
echo_thr()
