Firewall Punch Demo

Copyright (c) 2011 Sean Fisk

Licensed under the terms of the MIT/X11 license.

Description

Firewall Punch Demo is a proof-of-concept Java client and server to illustrate the UDP firewall punching technique used by Skype and similar programs.

It was inspired by an article on The H Security blog, The Hole Trick : How Skype & Co. Get Round Firewalls.

How to Use

Server

1. Download the Server JAR file.
2. Open a terminal in the download directory.
3. Run the server with

   java -jar fp_server.jar PORT
   

Client

1. Download the Client JAR file.
2. Open a terminal in the download directory.
3. Run the client with

   java -jar fp_client.jar HOST PORT
   

Running a server and two clients on the same machine

NOTE: This does not really demonstrate the real use of the program.

1. Open three terminals.

2. Start the server in the first terminal.

   java -jar fp_server.jar 5000
   

3. Start a client each in the remaining terminals.

   java -jar fp_client.jar localhost 5000
   

4. Once they are connected, kill the server with Ctrl-C.

5. Continue communication between the clients!