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So I’ve had this problem for a while where if I hosted a DOTA (or W3..etc) Internet game on a server, none of my LAN friends could join the game. They could see the game but attempting to connect would timeout or reject, even though my ports were forwarded and random people could connect.

Reason for Problem:

There are a few reasons for this:

• Some servers run a battle.net server clone using PvPGN. PvPGN has a “missing feature” when it comes to game advertising. The real Battle.Net servers are smart enough to recognize when two or more machines are trying to connect from a single IP address (ADSL connection, for example) and send back the internal IP of the host to its neighbours. The PvPGN server just sends back the Internet IP address to the host’s neighbours.
• Routers have to be smart enough or configured to perform “NAT loopback” or “Reverse NAT” or “PAT” for connections originating from inside the local network to the router’s Internet addressable IP address and port.

So if you are unfortunate enough to combine these two problems, your friends on your LAN won’t be able to join any Internet games you’re hosting.

Typical example in which your host’s IP address is 10.0.0.5 and your Router’s Internet IP is 66.1.1.2.

• Your host creates a game on the server.
• The server lists the game and all other people joining are told to connect to 66.1.1.2:6112.
• A buddy on your LAN (10.0.0.6) tries to join and is told to connect to 66.1.1.2:6112 as well. (A real Battle.Net server would tell it to go to 10.0.0.5:6112).
• Your buddy’s game tries to connect… which means it tries to connect to your Router’s Internet IP.
• The Router doesn’t have “NAT loopback” or “Reverse NAT” or “NAT on the inside” to forward internal requests (from 10.0.0./24) back into the network (to 10.0.0.5).
• Your buddy’s connection attempt times out, is rejected or fails.
• Your buddy goes back to his house to connect over the Internet. Everyone is sad.

Confirmed Working Router

I’ve found a good router which does NAT loopback out-of-the-box without any configuration.

It’s the Billion 7300G (RA) – ADSL 2+ Wireless 802.11g ADSL Modem/Router, 4 Port

I can confirm that this router works perfectly. It’s also quite a nice router.

Just Extra Stuff

Some routers will work automatically. Some will need to be configured. Some just won’t work. The thing with this is that it’s not really a feature that a router will advertise as having (like on the box or on it’s product page). You just have to know or test that it works.

Also, there are other methods for doing this – like setting your ADSL router into bridged mode – but this both increases the complexity of your network and exposes your internal machines directly to the Internet… so your security is compromised.