What is it?

A very simple TCP redirector written in python. It redirects any data sent to local port's to a target host, port. It acts as a bridge between local port and the target host, port pair.

You can run it by specifying a local port, target host and target host's port. For example the following will redirect all HTTP request to local port 8080 into Google web server

$ ./SimpleTCPRedirector localhost 8080 www.google.com 80

Why I wrote it?

I was not able to import a web service's WSDL document into SoapUI since all the related schema documents URI contains "localhost" as host name/address. I neither have control over the web service nor interested in downloading the documents and doing the changes manually. A quick search revealed "rinetd" and its Windows port. But still I wrote this script just to experiment the idea of TCP redirection.

The Source

#!/usr/bin/env python

import socket
import threading
import select
import sys

terminateAll = False

class ClientThread(threading.Thread):
	def __init__(self, clientSocket, targetHost, targetPort):
		threading.Thread.__init__(self)
		self.__clientSocket = clientSocket
		self.__targetHost = targetHost
		self.__targetPort = targetPort
		
	def run(self):
		print "Client Thread started"
		
		self.__clientSocket.setblocking(0)
		
		targetHostSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
		targetHostSocket.connect((self.__targetHost, self.__targetPort))
		targetHostSocket.setblocking(0)
		
		clientData = ""
		targetHostData = ""
		terminate = False
		while not terminate and not terminateAll:
			inputs = [self.__clientSocket, targetHostSocket]
			outputs = []
			
			if len(clientData) > 0:
				outputs.append(self.__clientSocket)
				
			if len(targetHostData) > 0:
				outputs.append(targetHostSocket)
			
			try:
				inputsReady, outputsReady, errorsReady = select.select(inputs, outputs, [], 1.0)
			except Exception, e:
				print e
				break
				
			for inp in inputsReady:
				if inp == self.__clientSocket:
					try:
						data = self.__clientSocket.recv(4096)
					except Exception, e:
						print e
					
					if data != None:
						if len(data) > 0:
							targetHostData += data
						else:
							terminate = True
				elif inp == targetHostSocket:
					try:
						data = targetHostSocket.recv(4096)
					except Exception, e:
						print e
						
					if data != None:
						if len(data) > 0:
							clientData += data
						else:
							terminate = True
						
			for out in outputsReady:
				if out == self.__clientSocket and len(clientData) > 0:
					bytesWritten = self.__clientSocket.send(clientData)
					if bytesWritten > 0:
						clientData = clientData[bytesWritten:]
				elif out == targetHostSocket and len(targetHostData) > 0:
					bytesWritten = targetHostSocket.send(targetHostData)
					if bytesWritten > 0:
						targetHostData = targetHostData[bytesWritten:]
		
		self.__clientSocket.close()
		targetHostSocket.close()
		print "ClienThread terminating"

if __name__ == '__main__':
	if len(sys.argv) != 5:
		print 'Usage:\n\tpython SimpleTCPRedirector <host> <port> <remote host> <remote port>'
		print 'Example:\n\tpython SimpleTCPRedirector localhost 8080 www.google.com 80'
		sys.exit(0)		
	
	localHost = sys.argv[1]
	localPort = int(sys.argv[2])
	targetHost = sys.argv[3]
	targetPort = int(sys.argv[4])
		
	serverSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
	serverSocket.bind((localHost, localPort))
	serverSocket.listen(5)
	print "Waiting for client..."
	while True:
		try:
			clientSocket, address = serverSocket.accept()
		except KeyboardInterrupt:
			print "\nTerminating..."
			terminateAll = True
			break
		ClientThread(clientSocket, targetHost, targetPort).start()
		
	serverSocket.close()

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