TcpGateway - A listen-listen TCP gateway in C#

TcpGateway is a listen-listen TCP gateway (Gender Changer, TCP relay) for Windows. It may be used to bypass NAT routers, e.g. for VNC, or for testing purposes.

Open-source. Written in C#.
Multiple gateways may be configured.
Each gateway listens on two TCP ports for incoming connections. When a connection is received at one port, the gateway waits for a second incoming connection at the other port. Then it joins the two connections by transferring all data between them. When one connection of the joined pair is disconnected, the gateway also disconnects the other connection.
As soon as two connections are joined, a gateway is ready to accept and join a new pair of incoming connections. Multiple joined connections may be active in parralel at the same time with the same two port numbers.
TcpGatewayService.exe may be run as a Windows service or as a console mode program.
Configuration parameters can be set in TcpGatewayService.xml.
InstallService.bat my be used to register TcpGatewayService.exe as a Windows service, and UninstallService.bat may be used to deregister the service.
To compile the sources, the .NET Framework is sufficient. No SDK or Visual Studio is required.

Download and Sources

Gateway classes source:	TcpGateway.cs
Windows Service source:	TcpGatewayService.cs
Test programs:	TestTcpGateway.cs, TcpStressTest.cs
Download full package:	TcpGateway.zip

How to use the Tcp Gateway with the Java VNC Viewer Applet

TcpGateway may be used with the VNC viewer applet. I recommend to use the RealVNC freeware version of vncviewer.jar. (The current UltraVNC version of the applet does not work with TcpGateway, because it opens two TCP connections, one before the password prompt and one after the password prompt).

The following HTML code may be used to place the applet on a HTML page:

<script src="http://java.com/js/deployJava.js"></script>
<script>
 deployJava.runApplet(
  {archive:"vncviewer.jar", code:"vncviewer/VNCViewer.class", width:"250", Height:"400"},
  {port:"1001"},
  "1.4");
</script>

The port number for the applet (1001) has to be one of the ports configured in TcpGatewayService.xml. The VNC server has to do a callback (add new client) to the other port using a host name like www.example.com::1002.

Author: Christian d'Heureuse (www.source-code.biz, www.inventec.ch/chdh)
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