CrossLoop Architecture

CrossLoop Architecture and VNC

CrossLoop is a proprietary shell program which uses the VIP Tunnel to negotiate a connection between two peer computers. After approval has been obtained from the HOST computer to accept a connection request from the JOIN computer, an encrypted and secure connection is established between the two peer computers using the VIP Tunnel. At that point, the CrossLoop shell program invokes the plug-in program which is specified in a companion XML shell script file. In the case of CrossLoop for Windows as it is currently released (Beta Version 1.0 Build 20061101161100), the CrossLoop shell uses fork and exec to invoke the TightVNC plug-in program.
   As the above CrossLoop Block Diagram illustrates there are no function calls made by CrossLoop to the VNC software (the Client/Server Plug-in Program) and they do not share any data structures. The only connection between the VIP Tunnel and the VNC is through TCP/IP. It is important to note that the CrossLoop shell program has no internal dependencies on VNC. To illustrate this point there are several other applications which use the CrossLoop shell and the VIP Tunnel and do not include VNC. Two of the programs are: Access My Files, a simple solution to remote file access ( www.accessmyfiles.com); and Remote Desktop Search, a free service that makes it possible to remotely access all of the information indexed by your Google Desktop anywhere in the world, (www.remotedesktopsearch.com).

The CrossLoop shell program uses an XML shell script as input to specify how the shell is to fork and exec the client and server plug-in programs after a secure connection has been established. Here is the CrossLoopApp.xml shell script file distributed with the current release of CrossLoop. This file can be found in the default installation directory,
c:\Program Files\CrossLoop\CrossLoopApp.xml:

You will note in the above CrossLoop shell script that it specifies the fork and exec on Windows of either the TightVNC winvnc.exe program in the case of a HOST connection (server), or the TightVNC vncviewer.exe program in the case of a JOIN connection (client).

CONCLUSION

In essence, the CrossLoop shell and VIP Tunnel enable the VNC to perform screen sharing between two computers on separate networks through firewalls. The identical function could also be provided by a VPN connection between the two computers on separate networks using the same GPL-covered VNC program.