Server Not Showing in Multiplayer Menu

I’m running a dedicated server for GMod, but I have problems with port forwarding. No-one is able to join my server, I used SPF (Simple Port Forwarding) to forward the ports, when I tested the ports… it said “success” but nobody is able to join it. The latency is very low (under 50) it’s obvious it’s LAN, I tried commands like “sv_lan 0” and “heartbeat,” both didn’t work. Does anyone know what the problem is?

Here is some information:
Server software: HLDSUpdateTool
Game: Garry’s Mod
Port running on: 27015
Port type: TCP
This is a dedicated server, not a crappy listen server.

What does your network look like?

Also you may want to ping the server and see if you get a response.

[editline]3rd May 2012[/editline]

I am going to need more details to how your network is setup.

Also try pinging the server from another computer and see if you get a response.

[editline]3rd May 2012[/editline]

sorry about the double post. I’m on a bad connection and the network timed-out for a bit there