TCP and Firewall support

Question

Hi all I m writing a TCP application but there are firewall... in a lot of companies. So I would like to know how I can create a TCP application with proxy support. I have search a lot through the web but cannot find any information. My application is a commercial application so I should be able to manage all kinds of proxy ! Please help me it is crucial Thanx

spgilmore · Answer

The http specification defines http proxy servers and how http clients can connect to remote hosts through those proxies. However there is not really a standard socket proxy server that I know of. For example I want to use a CVS client from my workstation at work but our firewall prevents it. I would have to use the Microsoft Proxy Client to allow me through the firewall by accessing the proxy server as a non-http client. I think this is Microsoft-Proxy 2.0 specific. If a firewall doesn't let your socket through you're out of luck. You could write a proxy yourself but you still need an open port that you can get through in order for it to work. You might as well just make the port configurable from the client app to begin with. If you could circumvent firewalls under every circumstance there would be no reason to use a firewall.