Nothing in the following post is new, its a compilation of approx. 50 some odd posts I read trying to get MP working. The following step by step process is what I used to get MP working for myself. I hope this helps.
Step by step guide to get MP working:
Step 1: ipconfig
From the cmd prompt, using windows XP, type the following:
Two bits of info are important, the Default Gateway IP address, and the IP address. The Default Gateway is the IP address for your DSL modem, cable modem, etc. The IP address is not your "real" IP, but your NAT that resides behind the "gateway" to the Internet, your modem.
They should look like this:
NAT IP address 192.168.x.x
Default Gateway 192.168.x.x
If you have multiple computers off the same modem, each will get their own NAT, usually, a single digit different from the Gateway address. Even if you have multiple PCs sharing an Internet connection, they all can't play the game simultaneously because you only have a single gateway, and thus can only forward to a single NAT IP at a time, see step 3.
Step 2: www.showmyip.com
To play MP over a direct Internet connection, you'll need your "real" IP, or also referred to as your public, or WAN IP.
The easiest way to get your WAN IP is to access www.showmyip.com. In the upper left of the web page, your public/WAN IP will be displayed. If your ISP provides you with a "static" IP this number will never change, if not, each time you reboot the PC, lose power, or have to re-connect to your ISP, this # may change.
Step 3: Firewalls
Using the default gateway IP from Step 1, enter this # into your web browser's address line. This is where its going to get difficult. Every modem manufacturer and ISP uses a completely different interface. Elsewhere on the HOI forum you'll find a sticky leading to examples from a few firewall interfaces, please use them as a guide.
Basically, after entering the default gateway IP, you are now into your modem's settings screen. If your modem or firewall is administrable you'll be able to access your firewall settings. Many, older, or first generation DSL modems are not, you are forwarded to a webpage that's basically just an info screen, you'll have to contact your ISP to get an administrable modem, this happened to me, and the ISP charged me $60 for the new modem, great eh?
In addition, many ISPs are going to require a username, and password to access your modem's settings. Fortunately for me, mine did not. If a user name and password are required, you will have to contact your ISP for that info.
Okay, now that you're in, you need to adjust your "port forwarding" on the modem. This allows IP traffic that hits your modem's firewall, the game info, to be forwarded to your IP behind the Gateway, to your NAT IP, from step 1.
Nearly all systems refer to "port forwarding” settings in the advanced settings are of the interface. Once there you have to input the following port ranges to allow the game to find your PC behind the gateway.
Most systems after asking for the specified range will ask for UDP, TCP etc, the game requires TCP forwarding. You now need to use your IP address from step 1, as this is your NAT IP behind the gateway, the 192.168.x.x number.
Another problem may arise in regards UPnP, if its active, you may not be able to connect either. This is a software feature that is supposed to make forwarding over ports easier, however, it doesn’t always work. This feature was not an issue for me, as my router did not utilize it. If yours does, you must disable it, again, check your modem settings and your ISP for more info.
Also, if your modem requires that IP addressing, or IP Routing needs to be turned on, that feature may need to be activated prior to getting the “port forwarding” feature to become available.
See I told you step 3 was where things would get difficult.
Be sure to use your system's save and restart feature, don't "x" out of the window, because unless you save and restart your modem, your new setting changes will not take affect.
Turn off all software based firewalls on your PC during play. If the specific firewall program allows you to give Internet permission to specific applications, you may also use those options, and not have to turn off the firewall.
If the above settings and forwarding do not work, or if you have a modem setting that does not allow for the input of port ranges, but does allow for DMZ hosting, DMZ may also work. If you chose the DMZ option, it essentially opens up your PC to all Internet port traffic unrestricted to your PC during the play of the game. Once the game is completed please turn off the DMZ option to secure your PC.
If you are going to use valkrie net you're done, you should be able to use that interface to get a game going no problem...
If you want to play directly over the Internet in the event valkrie is down, you'll need the WAN IP from step 2.
Step 5: Direct IP play
Select the Internet option from in game. If you are hosting, provide your WAN IP to your opponents. They in turn enter this into the IP space provided in game, and they select the Join option. If everyone has set their options as in Step 3 and Step 4, everyone should be able to join.
I can not guarantee all the above will work, since every user’s situation is different. Thus, this is why Paradox does not go into great detail on MP setup. Legally, they would be open to all sorts of issues. I too will post the disclaimer that if you run into trouble, get hacked etc, that you did so, fully knowing the risks going in. All of the issues making this game so difficult to use MP are the result of the world we live in.
Many game manufacturers that support online gaming spend thousands of dollars to invest in servers that do all this work in the background, and function as the server hosting your game. In the realm of Paradox, the host’s computer is that sever, thus you have to go thru all of this pain to make it work.
Hope you enjoy the MP experience, if you would like to ask me a specific question in regards to MP, send me a personal message thru the forum and I’ll try to help as best I can. If you wish to add to this post with comments and or questions, please do so, and I will try to respond promptly.
Good luck and good gaming to all…..