forward traffic from port X to computer B with c# “UDP punch hole into firewall”

Question

I need to establish a tcp connection from my house computer to my office computer.

on the office there is a router where several computers are connected to. that rou

Answer 1

You could write your own proxy:

Server: Listen on 1300 for connection from A, and on 1301 for connection from B. Keep a list of both connections, when you have at least one of each, create a proxy object. At this time you signal your connection from B that you have a connection, which could be a signal byte or a port and even address to connect to. After that when you get data from A, send it to B. When you get data from B, send it to A.

Computer B: Program maintains a connection to port 1301 on Server. If the connection ever drops, re-establish it. When you receive a signal (could have address and port or just be an "I have a connection" byte), create a connection to the desired port and store the two connections in a proxy object. When you receive data from one, send it to the other. Since you're using that connection, establish a new connection to port 1301 on the Server to handle more.

You'll have to handle dropped connections of course, sending a keep-alive signal between the always-open pending connection between B and the Server will help.

Here's a sample class I wrote a long time ago to do the proxying. I don't have time to clean it up, but if you see TcpProxy that is a parent class that accepts a connection, the Client is the accepted connection and RemoteEndPoint is the end point to connect to. It also writes the data to a file and does some other stuff you can ignore.