Netplay Guide

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.

Requirements

 * Bandwidth requirements are very light: any DSL or Cable internet connection should do. However, the internet demands rapidly increase as more players are added. Because the latency (ping) of the internet connection determines how low input latency can get, using Ethernet instead of Wi-Fi usually improves the gameplay experience.
 * Each player must have their own copy of the game, and the region and game revision of all copies must match. While most compressed game formats are compatible with standard ISOs (with NKit being a notable exception), it is heavily recommended that all players use identical dumps.
 * All players must use the same Dolphin version. Newer Dolphin versions are more likely to have fixes for Netplay. Many users opt to use the latest beta versions from the official website. It can be isolated from your main Dolphin profile by using "portable.txt" or creating a special shortcut. Dolphin will not allow users to use mismatched versions for Netplay, to prevent desyncs.

Setting Up Dolphin
Your Netplay Experience will greatly vary depending on what version you tend to use. Because Dolphin 5.0 is lacking so many Netplay features at this point, it cannot be recommended for use. It is missing important features like Wii Save Synchronization, Automated Settings Synchronization , Cheat Code Synchronization , Synchronize All Wii Saves as well as protections for recovering saves if Netplay is to crash.

Rule of thumb is that most settings should be set to default and you are expected to follow specific settings where the instruction (made by host or matchmaking websites) has told you to set before playing online.

Hosting or Joining a Session
Under the tools menu, you can find the option to "Start Netplay Session". From there you have several options.


 * Hosting a session allows you to pick a game and host it for others to join. If you use version or newer, you can also host these games publicly with the "Netplay Server Browser".
 * When hosting a session, you can choose whether to Direct Connect or use a Traversal Server. Both will have the same latency, however using the traversal server allows you to use a host code instead of your IP Address. Depending on your router, you may not even need to port forward when using the traversal server.
 * You can join a session by browsing public Netplay sessions or going to "Start Netplay Session" to get to the page where you can join sessions. You can enter a host code or IP Address as needed in the "Connect" tab.

While Dolphin does try to automatically configure and sync settings to be correct, it is important to be familiar with settings that can affect Netplay.

General Configuration
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Wii

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 * Deterministic Dual Core Netplay is now merged into master. While compatibility is not perfect, it should allow more games to work on dual core with three exceptions. Games that require Skip EFB Access to CPU, Store EFB Copies to Texture Only and/or Store XFB Copies to Texture Only unchecked in the Graphics > Hacks settings are not guaranteed to run correctly. Deterministic Dual Core can be faster than Single Core in some games, but may also be much slower if a game relies on certain visual effects. Single Core mode in Netplay is the same single core mode used outside of Netplay and has no compatibility penalty.
 * SD cards do work on Netplay but must be manually synchronized. Any difference at all in the SD card, no matter how minor, will cause desyncs in games that access the SD card.

Settings Synced
As of, most settings that affect determinism will be synced to other clients, so only the host needs to ensure correct settings. Games which use EFB reads or EFB to RAM are likely to desync with mismatched graphics settings, therefore Strict Settings Sync should be used, which will additionally sync most graphics settings except for backend.

On older revisions, only these settings will be synced over:
 * Advanced Settings from General menu
 * Misc Settings from Wii menu
 * CPU Options from Advanced menu

Note that over long periods of time, using different video backends may eventually cause a detected desync. However, because not all target operating systems support all backends, Dolphin will never attempt to synchronize graphics backends. If you do see a seemingly random detected desync during very long play sessions and you are using different graphics backends, this is usually the cause. These desyncs usually do not manifest in anything immediately broken, but it is still recommended you save and restart to prevent issues.

Graphics Configuration
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Hacks

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 * Most settings under Enhancements menu can mostly be turned on or off without incident on higher end processors. The only exception to this is when an enhancement breaks a game, such EFB Copy readback. If a game requires EFB Access from CPU or EFB Copies Stored to RAM for game mechanics, the game may freeze or run slowly unless you use Single Core. It is highly recommended you do not change these settings while Netplay is actually in session, however.

Controller Settings

 * Enable and configure GameCube controller port 1 for your controller (this applies to both host and joiners). If you're attempting to use a Native GameCube Adapter for Wii U on netplay, make sure the controller port is set to that in the controller configuration.


 * If you're attempting to GBA <-> GCN netplay, the same rules apply as GameCube Controllers with some key differences. Much like GameCube controllers, it will pull the controller configuration from the first available controller port's settings, but you also have to enable the GBA controller in the netplay settings window.  For setting features like a "default ROM" on netplay, this actually is configured *per port* and will not grab information from the first port.  As a note, all GBA saves are synchronized from the host, even for GBAs that they're not controlling.  GBA <-> GCN netplay requires  or newer.


 * Wii Remotes are far more particular about how they are setup in Netplay. Unlike GameCube Controllers, you must configure the Wii Remote you are assigned to in the Netplay lobby. As such, Player 2 will use their Wii Remote 2's configuration. Once Wii Remotes are configured correctly, they usually work fine for the remainder of the session  If you notice any desync while playing with emulated Wii Remotes, it is highly recommended you save immediately, as a desync in Wii Remote reporting modes will crash the emulator.

How to set the Pad buffer
Because input on the GameCube and Wii are polled by non-frame intervals, buffer does not directly relate to frames and can even vary per game. Lower the buffer as much as possible without causing slowdown for an optimal experience, ideally in areas that insure there isn't computer related slowdown such as a menu. In most games, add roughly 1 pad buffer per 15 ms of latency per client. Two players at 50 ms latency would be roughly 3 - 4 buffer, where as three players at 50 and 65 ms would be roughly 7 buffer.

Assigning Controller Ports
By default, only players of the first port on each computers will be used. The host will be player one, and the first joiner will be player two, and so on. But the host can change the port order and invite the secondary players of the same computer. To do so, simply hit the "Assign Controller Ports" button, then add and/or order their names to the port number respectively.

Setting a Spectator
A Spectator is a connected computer that has no controllers assigned to them. Any player can be turned into a spectator by going to the "Configure Pads" window (only host has access to it) and remove the their name from the controller ports. The spectator will not cause lag or latency but can still watch the Netplay session.

Host Input Authority
This gives the host control over when inputs are sent to the game, effectively decoupling players from each other in terms of buffering. This allows players to have latency based solely on their connection to the host, rather than everyone's connection. Buffer works differently in this mode. The host always has no latency, and the buffer setting serves to prevent stutter, speeding up when the amount of buffered inputs exceeds the set limit. Input delay is instead based on ping to the host.

This can result in smoother gameplay on unstable connections, as well as allowing players with much higher latency than others to play without increasing everyone's latency. However, this comes at the expense of latency fairness, which may make it not suitable for competitive play.

Golf Mode
This addition to Host Input Authority allows the player with no input latency to change mid-game. This is incredibly useful for games where only one player is playing at a time, like a golf game. Do note that all other players experience a latency penalty in this mode, so it should only be used for games where only one player is playing at a time.

Reduce Polling Rate
This option used to significantly reduce the polling rate in order to lower network usage. However, it is no longer necessary in the latest development versions due to a bug fixed in how much controller data was being sent.

Desync Troubleshooting
Double check your settings and confirm if you and other players have good ISO dump. Dolphin added the ability to detect desyncs. Watch the textbox for desync notifications, as very often it will be able to tell the game has desynced before the players and may help them pinpoint the problem.

Netplay has matured considerably in recent time, but still requires user competency and problem solving to get over some of the hurdles. Never ignore obvious problems such as Game ISO differences or SD card differences, as those are not synchronized by Netplay for obvious reasons.

Netplay Between Different Recompilers
Dolphin can run on both AArch64 and x86-64 devices, but because of the sensitivity of how the JITs work, we cannot guarantee that netplay sessions between different architectures will work. In initial testing, games do sync, but a desync message due to some timing differences will be displayed rather early on regardless. It can work, but is not supported.