I figure I could take a crack at making a tutorial for this, so we can get more people playing online. 
Table Of Contents:
Step 1: Downloading
Step 2: Initial Setup
Step 3: Game Setup
Step 4: Net Play and Controller Setup
Step 5: Playing Online
Step 5.1: P2P Hosting
Step 5.2: P2P Joining
Step 5.3: Using a Server to Find or Host Games
Step 1: Downloading
First, you’re going to want to download the newest Demul (at the time of writing this tutorial, it is 0.5.6 WIP)
Link: DEMUL - Sega Dreamcast Emulator for Windows
Next, grab the newest netblade plugin. Currently, the newest version is 0.45.
Link: [REMOVED]
UPDATE: THE NEW VERSIONS OF NETBLADE WILL DESYNC. STICK WITH THE ORIGINAL 0.38 UNTIL NOW (DOWNLOAD HERE: http://www.emuhq.com/download/7003/).
Of course, you should always check to see if these are the newest files from the official sites.
Step 2: Initial Setup
When you first download and extract Demul, you’re going to get a folder like this:
Open Demul by clicking the Demul file in the folder. You will get a “BIOS & Plugins not configured” message. Click Ok.
This will appear:
At this point, you can configure whatever options you need to, or you can come back to it later. You’ll notice that there is no Net Play plugin. We’ll go ahead and take care of that now.
Extract the netBlade_v0.42(Windows) into it’s own folder somewhere else. Then, drag and drop kailleraclient.dll and the netblade.ini file into the demul folder. Place the netBlade.dll file into your plugins folder.
Now when you go back to your Bios & Plugins page, you’ll already have the Net Blade plugin in the spot it needs to be.
Step 3: Game Setup
While this step is usually easy for most games (throw the games and bios into the roms folder and play), MvC2 is a little tricky. Most of you will get an error that mpr-23083.ic31 is not the correct file size, and that would be correct. It’s actually mpr-23083.ic31 and mpr-23084.ic32 that are the wrong sizes, and quite frankly I don’t know why.
What I do know is that I have a nifty little pack you can download that does NOT CONTAIN THE ROM FOR MVC2, only the files you need for it, including the fully unlocked nvram so you don’t have to do those fussy unlocks.
Link: Download
You really need to pay attention to this next part so that you don’t overwrite the files you need.
Before doing anything with my pack, first check your mvc2 file. Is it a .zip or some other compressed format? If so, unzip it. Then, unzip my pack into your demul folder, overwriting both mpr-23083.ic31 and mpr-23084.ic32. The nvram for the game will also be placed into the appropriate folder at this time. If you would like to, you can go ahead and re-zip/rar/whatever the mvc2 folder, or you can just leave it how it is. Demul will read it either way.
Now that we’re done setting up the game itself, let’s move on to setting up Net Play and your controller.
Step 4: Net Play and Controller Setup
First, go to Config -> NetPlay and you should see this screen:
Check the box next to “Enable NetPlay”, then click OK.
Next, go to Config -> Game Pad. Since we’re dealing with arcade games, you’re going to want to set up the JAMMA controls. Choose “Joy 1” under JAMMA and click each button to set it to a key or your arcade stick. Lucky for us, MvC2 just went right down the list of buttons in a really simple order. 1, 2, and 3 are LP, FP, and A1, respectively, while 4, 5, and 6 are LK, FK, and A2, respectively.
After setting up your buttons, click OK, then OK again to go back to the main Demul screen. Then, go to File -> Run Naomi and choose Marvel vs. Capcom 2. The Net Play window will then appear.
Step 5: Playing Online
The following steps will get you started with playing online, whether its P2P or via a server. One thing I’ve found out is that it’s a very good idea to put the game on freeplay and have the same nvram files if possible. Having different amounts of coins in or trying to insert a coin will desync the game, so it’s best to just put it on freeplay.
Step 5.1: P2P Hosting
At the Net Play window, make sure the “Mode” on the right side is set to P2P. Choose the game you want to host, then click Host at the bottom (See reference below).
If a windows firewall message appears, just click “Unblock”.
A “Connection Window” should appear. To get another player join, simply give them your IP address and have them follow the instructions below. After both players are in the room, they will need to check the box labeled “click here when ready”. The game will start for both players, and both players will need to press start in order to play against one another (or insert coins first, if necessary).
Step 5.2: P2P Joining
At the Net Play window, make sure the “Mode” on the right side is set to P2P. Click on the “Connect” tab, and enter in the host’s IP address in this format: [ip]:[port]. For example, 127.0.0.1:27886. The port is almost always going to be 27886, and should not be changed unless you and the host really know what they’re doing.
Click Connect, and a “Connection Window” should appear. Check the box labeled “click here when ready”. After both players have done this, the game will start. Both players will need to press start in order to play against one another (or insert coins first, if necessary).
Step 5.3: Using a Server to Find or Host Games
At the Net Play window, make sure the “Mode” on the right side is set to Client. Click “Custom IP” at the bottom if you know the IP address of the server you want to connect to, or click “Master Servers List” if you want a list of servers to connect to (See reference below).
After clicking “Master Servers List”, a list will appear of different servers. Pick a server with a good ping and click “Connect”.
A list of games will be at the bottom. Join a Marvel vs. Capcom 2 game by double clicking it. The host of the game will then start.
To create a game, click on the “Cr” button next to the “Chat” button, go to “Create”, then “Marvel vs. Capcom 2”. After another player has joined, Click “Start” to start the game.
The End
FAQ:
Q: Why isn’t the Game Pad config recognizing my joystick when I press buttons?
A: First thing you want to do is make sure windows is recognizing the joystick. If it is, but Demul still isn’t, try switching the “device api” at the bottom of the config window. I actually had to flip back and forth between dinput and xinput before my arcade stick would work correctly.
Q: I don’t have access to gpuDXv3 or gpuDXLegacy. What’s wrong?
A: You will need to reinstall DirectX, even if you have it already. Just grab the newest redistributable (DirectX End-User Runtimes (June 2010)), install it, and you should be good to go.
Q: I get the error “[NET] LoadLibrary( “kaillerclient.dll” ) failed.” after starting up a game with Net Play. What’s wrong?
A: Make sure kaillerclient.dll is in the MAIN Demul folder, not in your plugins folder. Then it should work fine.
More FAQs when people ask more questions that are answerable. Feel free to submit some.
I hope this has helped some people out so we can have more players online who play fighters.
Enjoy :3
