HELLO ALL you (Newbs And Pros) People!
I have been hosting lately with this kind of technique on srb2 for a while...
NO MORE USE FOR DEFAULT PORTS... YAY!

There is ONE way to host srb2 without using the DEFAULT ports... If you have existing Ports in your computer here's how to find them.
Start Menu -> Computer -> the scroll box, find network -> right click the gateway device, and select properties -> click the settings box -> Find a existing port -> Edit it so the port number is 4 numbers...
Now, exit all that stuff and here's what i do with that port.
(optional Steam)
add srb2 to your steam library and right click the name and select properties.
At the end of the target name... Add "-udpport" Then put the port you already have in there...
example...
"C:\Users\(USERNAME)\Desktop\srb2\srb2win.exe" -udpport 3698"
That's my directory, of course.
(THE SRB2 LAUNCHER WAY)
Almost same as above.
Just launch the srb2 launcher, then go to the command line perimeters. then add
"-udpport" Then the port you have. Then LAUNCH!
CONGRATULATIONS, YOU CAN HOST SRB2! c: