Netplay is a defining feature of Dolphin: it allows you to set up online sessions for any GameCube or Wii title with a local multiplayer mode, without the problems or limitations of the Nintendo Wi-Fi Connection or hassle of the BBA. It is improving regularly, and GameCube Netplay should be painless. Wii Netplay is much more temperamental and should be treated as an experimental feature for advanced users. Netplay is only for the Desktop version of Dolphin. Dolphin on Android does not currently support Netplay.
This is a desync. Basically what both of you are seeing are two different games. See Desync Troubleshooting
Your Netplay Experience will greatly vary depending on what version of Dolphin that you are using. Because Dolphin 5.0 is lacking so many netplay features, we highly recommend to use either the latest available beta or dev build. Dolphin 5.0 won't have have Wii Save Synchronization (5.0-8478), Automated Settings Synchronization (5.0-8502), Cheat Code Synchronization (5.0-9032), Synchronize All Wii Saves (5.0-9037) as well as protections for recovering saves if Netplay crashes. If you're looking to play a Wii title that requires using Wii Remotes and/or their attachments, it is highly recommended to use 5.0-17527 or newer as Wii Remote Netplay has been rewritten and standardized to netplay conventions.
If you're inexperienced with netplay, then the biggest rule of thumb is not to change too much and try to follow this guide, as it will go through most of the important things to know. The following information reflects the latest available development build as of its writing.
A Netplay Session in Dolphin is started before actually running a game. You can setup a netplay session from the Tools Menu -> Start Netplay Session for options for joining or hosting a netplay session. If you wish to join a public netplay session, you can use the "Netplay Server Browser" available in 5.0-8478 or newer.
If you wish to host netplay session, there are a few things to keep in mind. You'll have the option to select a specific port, along with host via direct connection or the traversal server. You can also set a name for yourself so that you can be identified in the player list.
Once you've selected a game and are finished, you'll enter the host netplay menu. If you've hosted via the traversal server, then you'll have a code to distribute to the players. Otherwise, you'll need to distribute your IP and port. Note that if you're behind multiple routers, there may be additional complications. You may need to manually obtain your IP Address if Dolphin displays a local one when using Direct Connect.
Do note that you can host on the traversal server, but still allow certain users to direct connect if you trust them with your IP. This is particularly useful for LAN games, where the traversal server connection method will not work. You can allow outside players to connect over the traversal server while you can have local players connect directly with your IP and port. Note that using the Traversal Server does not add any latency - it is only used for connectivity.
The host of the netplay session has additional responsibilities, such as configuring the input buffer, enabling/disabling various netplay features, and assigning netplay controllers for all of the players.
Joining a netplay session is simple. Simply set your name to whatever you want it to be, and enter the host's traversal code or IP address depending on how they've hosted. If using direct connection, you'll need to connect via the host's IP Address and the port they are hosting on. Once you've joined the netplay session, you simply need to wait until the host starts the game.
If you're unable to connect, there are a multitude of common reasons.
Because every router is different, you may need to consult a guide specific to your router in order to port forward.
Once a session is hosted, the host has the opportunity to adjust netplay settings before actually starting the game. These settings may be crucial to the enjoyment of your netplay session, so please review them carefully.
The Checksum tab is a very powerful tool for verifying files that Dolphin cannot synchronize between players. It can be used to check and see if every player has a proper, matching dump of the game attempting to be loaded. If you're having desyncs that you cannot solve through other methods, be sure to use the checksum tab to verify that everyone's game (and SD card, if applicable for the game you're playing) matches.
The other tab has a few extra settings that are applicable in rare situations. These are extra settings you may or may not want to have on, and some of these settings can be accessed by the client.
Setting up netplay controllers is a very simple system. Note that as of (5.0-9037), Wii Remotes now follow the standard configuration procedure. If you need to use Wii Remote netplay on an older build, please skip to the later part of the guide.
When using a Standard Controller for netplay, it's very simple to configure things. If there is one player on each computer, then Dolphin will automatically map things correctly on its own.
In this setting, Dolphin takes whatever configuration is in Controller Port 1 of User and maps it to port 1 of the netplay session. For User 2, it takes whatever controller is mapped to Controller Port 1 and maps it to port 2 of the netplay session. This means whatever configuration is in controller port 1 for each player is used for their netplay controller. This keeps things simple, so that a player doesn't have to map port 4 just to play on netplay - Dolphin will grab from the first available port! This applies for up to 4 separate players. This is specifically for when one player is on each computer.
Remember, each player does not need to configure the controller for the port they are in with this situation. Dolphin will grab whatever controller profile is configured to the first GameCube Controller Port in Options -> Controller Settings.
As a note, the Native GameCube Adapter for Wii U is also supported, and just needs to be assigned to the first controller port in this example.
If you have two or more friends connecting from the same computer, you can give a single computer multiple controllers. In this example, the user labeled "friends" has two players wanting to play from the same computer. In this case, the host goes to "Assign Controller Ports" and simply gives that player's computer two controller ports.
Now "friends"'s computer will have control of controller ports 2 and 3 during the game. However, much like before, they only need to configure the first two ports of the Controller Configuration page. Dolphin will give the first controller's profile to the first assigned instance of their PC, and the second controller's profile to the second assigned friend. This can be done with the host as well, by simply assigning the host's computer to multiple controller slots.
If you want someone to be able to watch without impacting latency, you can do that simply by removing them from any of the controller slots. If a spectator's computer lags, the actual netplay match won't be disrupted and the spectator will simply fall behind.
Since 5.0-14690, Dolphin can use GBA Controllers on netplay via the Integrated GBA powered by mGBA. This can be used to play GBA <-> GCN games on netplay. For games like the The Legend of Zelda: The Wind Waker, you can assign one player to play the main game and another to play the Tingle Tuner. On Four Swords Adventures, you can assign each player a GBA for multiplayer mayhem. The list goes on, and even Pokemon Colosseum and Pokemon XD battles can be played on netplay... with some extra setup. Please refer to the the Integrated GBA guide to make sure your Integrated GBA is functioning correctly before attempting to use netplay. Each player must have a GBA BIOS configured that the Integrated GBA can automatically load.
The same rules apply for GBA controllers - Dolphin will pull from the first controller profile possible from each computer when assigning controls. If a computer is given multiple controllers, it'll assign the first port, then the second, etc. This means each player will need to at least configure the Integrated GBA in port 1 in order for their controls to work. If you have not configured it yet, it will use the default controls which may not be suitable for normal gameplay.
You do not need Integrated GBA currently set as the controller in the port. The important thing is to just make sure that the controls are set so that Dolphin has an input profile to pull from. For netplay, the GBA itself is actually enabled in the Netplay Window under Assign Controller Ports. Let's say that Player 1 is controlling Link in Wind Waker and Player 2 is controlling the Tingle Tuner.
Assigning multiple players to GBAs is just as simple as checking more of the boxes.
The two Pokemon titles are among the most complicated to play on netplay simply because they require GBA ROMs of the GBA games, and they require savefiles. All of the same rules apply that apply for normal netplay, with a few more limitations
If everything is done correctly, each player can reset their personal GBA (by right clicking on it and hitting reset) in order to reload the BIOS and trigger connectivity when the GameCube game is ready.
As of 5.0-17527, Wii Remotes mostly work the same as other controllers. You have to use Emulated Wii Remotes on netplay. If you would prefer to use Real Wii Remotes on netplay, you must do that through Emulated Wii Remotes via the Connect Wii Remotes for Emulated Controllers. Your Wii Remote will now show up as an emulated controller that can be assigned buttons, and with Dolphin's Wii Remote with MotionPlus Pointing (Stock) profile, you can automatically assign everything exactly how it would be if you were using it directly as a real Wii Remote. The "Real Wii Remote" controller option itself is not supported on netplay.
On older builds, Wii Remote Netplay was a lot more confusing to setup due to the fact that controllers were not automatically reordered like with standard controllers. Each player must set a configuration profile to the Wii Remote Slot they will be using on netplay. That means if you are the host and using Wii Remote 1, you must have the first Emulated Wii Remote configured to your controller on your computer. If you are a client joining and you are assigned to Wii Remote 2, you must have Emulated Wii Remote 2 configured with your controls. In order to prevent desyncs, all players should configure the correct attachments to all controllers. Though Dolphin should attempt to synchronize attachments, it has been known to have issues. If you are using a physical Wii Remote connected as an emulated controller you do not have to set the attachment ahead of time as the stock profile automatically configures it.
Wii Remotes in general are very sensitive to desyncs, and there is a chance that any kind of desync will cause netplay to entirely crash. We recommend Wii Remote netplay is only attempted by advanced Dolphin users. If a Wii game supports GameCube controllers, we highly recommend using them when possible. Wii Remote Netplay should be considered an experimental feature.
There are many reasons as to why a desync could happen. These are the most common reasons we've seen for a potential desync.
For lockstep netplay to work, all players must create an identical emulated environment on all PCs. If one player has an ISO with a defect, then they may not sync with other players. Please refer to the Checksum options explained above for more on how to detect these issues.
If you have the SD Card enabled in the Options -> Configuration -> Wii tab, then it may be the cause of your desyncs. We recommend unchecking it whenever possible for Wii Netplay. If you must use the SD Card as part of your netplay session, please ensure that the SD Card is identical before starting with the SD Card option in the Checksum tab in the netplay Window.
The AArch64 JIT and the x86-64 JIT can produce very slightly different code which is enough to trip Dolphin's desync detection. Usually these desyncs do not actually affect the game, but it also means that desync checker won't be able to detect more serious desyncs. We do not recommend netplay between different CPU architectures unless all players involved are advanced users.
If you do not enable save syncing but have memory cards enabled, you may cause a desync. We recommend enabling save syncing to bypass this.
Wii Remotes are extremely touchy with how they're configured and if they're configured improperly, they may cause desyncs on their own. In order to test if the Wii Remotes are the cause of the desync, you can simply assign GC controllers instead of Wii Remotes for the game. Even if you can't control the game, if you see that the game runs without desyncs without Wii Remotes configured, then you know the problem is with the Wii Remote. Reconfiguring the Wii Remotes and their attachments may solve this issue.