Creating a Network Connection Between Two Computers Behind Routers

[Alkatran]

I live in a university apartment, behind a router that blocks all incoming connections. My friend is in the same situation. But we want to be able to create a network connection between our two computers.

What can we do? I know there are proxies out there that will forward connections, but that's no good since the proxy connection would be blocked anyways. Are there any 'server' proxies that accept two incoming connections, then ferry data between them? (Obviously not counting things like gaming or instant message servers, since they don't ferry arbitrary data)

 

[Ranik]

Well, If you can use the internet ... then set up some form of tcp/ip or udp connection using port 80... it has to be open if you can browse the internet.

Also, get a port scanner and see what ports are open and what are closed. This might allow you to establish a VPN.

Common ports to try : 80, 1494, 3396

 

[Alkatran]

I thought all browsing was outgoing connections? I'm essentially behind a stateful firewall, so I thought incoming connections, even on 80, would be blocked?

 

[BoredNL]

I thought all browsing was outgoing connections? I'm essentially behind a stateful firewall, so I thought incoming connections, even on 80, would be blocked?

Of course incoming connections on all ports won't end up at any computer unless the router is set up to forward the ports to the computer. (which computer should incoming connections on port 80 be sent to? The router doesn't know unless you tell it.)

You can either pay for a proxy service, use a free HTTP proxy (and then use port 80 to establish the connection, but any proxy service is going to be pretty slow), or one or both of you can configure the routers you are behind to forward certain ports to your local computers (do it yourself, or make friends with the network administrator if it's not a home network).

Note: If one person is able to get certain ports opened and you are using a program such as AIM, sometimes the connection will work in reverse. For example, if you were to get port forwarding set up on your network for your computer and your friend were to try to make a direct connection to you from AIM or IRC, it might not work because (at least with older versions of AIM), the direct connect request actually includes your friend's IP information, which your program will then use to connect to HIS computer, so it will seem like he was not able to direct connect to you and that the port forwarding has failed (which won't be the case). You will want to try direct connecting from both sides, if only one of you are able to get port forwarding set up.