Dark Souls: How to Prevent Invasion / See Summon Signs Instantly

Dark Souls: Summon Friend Instantly
In Dark Souls: Prepare to Die Edition, the whole multiplayer connection is different than in the Xbox 360 and PlayStation 3 (PS3) versions of the game. Specifically, it is p2p (peer-to-peer) with IP Pools cycling.
In other words, you sometimes have to wait a very long time until you see a summon sign dropped by your friend -- or if they want to see your summon sign. So if your friend's summon sign isn't showing up, that's why.
Literally, it is not unusual to have to wait 20 minutes or so. During that time, it is likely you will be invaded too, and killed since many players like to cheat.
This solution solves both problems -- it stops invasions and lets you see White Sign Soapstones or Red Sign Soapstones right away.
So to Stop Players from Invading You, follow the same steps as below.
Dark Souls: Fix Multiplayer Summoning
Basically, we will limit the IPs able to connect to you in the game -- immensely.
1) Download Tunngle and install it
2) Sign up for it and login, then using Tuungle join the "DARK SOULS: PREPARE TO DIE" room
3) Check your Tunngle connection settings for Port Forwarding and hit "test connection" to see if it is working. If it isn't working, then either your firewall OR your router is blocking the port, and you will need to open them through there.
Done! Now just open Dark Souls and you're good to go. Only the people in that room will be able to join your game (and there aren't very many) so it's like playing via LAN.
Invasions are possible still, but unlikely (feel free to join a DIFFERENT room to avoid invasions altogether). It's kind of like playing in offline mode that way. Works on Steam copies of the game too.
Note: If you don't want to do all that and are trying to join a friend for coop, then it helps if you try to use the "join room" option through Games for Windows Live (GFWL).