Mario Netplay

Copy pasting this from another guide tailored towards Mario Party, should work fine with other games too.

Netplay Setup Guide
Step 1: Download the Emulator

PJ64 (Mario Party 1-3)
Download: https://mega.nz/file/ojYChBaJ#LLrSDAVh51fVO8notunG9gil_nsne3JRksrfR5jGyXs
Mirror: http://www.mediafire.com/file/xi683kuiqzdwmop/Mario_Party_Netplay_64.7z/file

Dolphin (Mario Party 4-9)
Download: https://mega.nz/file/hmZSiJjC#OsC8Wx9qX5Ifqcn9Ekd8esfKPJZB7_kExR8M7bL57Ro
Mirror: http://www.mediafire.com/file/5ub2ra5t82dkm7y/Mario_Party_Netplay_GC-Wii.7z/file

This download contains a custom netplay build, which includes 100% saves, optimized netplay settings, game-enhancing codes and more.
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Step 2: Gather Your Games

Obtain ISO files for the games you would like to play. (https://vimm.net/?p=vault)

Note that only version 1.01 of Mario Party 4 and version 1.02 of Mario Party 8 are supported; If you have another version of Mario Party 4, you can use the converter included in the Extras folder of the download.

Make sure your ISOs match the following checksums:

Mario Party 4 (USA) (v1.01).iso: 01de13ad52f1554975e7f316370ba086

Mario Party 5 (USA).iso: 6b3699ee1f18447c4b2fabb3dd2ebf39

Mario Party 6 (USA).iso: 010dece78287bcb8cafdeb15f035127a

Mario Party 7 (USA).iso: bd367c67fca5d93e581a43d1f61f4514

Mario Party 8 (USA) (v1.02).iso: 944c3f7db81170c9d86fc73dab1da24b

Mario Party 9 (USA) (En,Fr,Es).iso: a9aa140b48e67ccdba9c7c9afc9884bc

You can confirm your checksums by right clicking on the game you're testing and selecting Properties > Verify > Verify Integrity.

To prevent lag you need to convert your nkit isos to regular isos
https://vimm.net/vault/?p=nkit
this page has all the programs needed to do so
_________________________________________________________________________________________________________________________________________yStep 3: Set Up the Emulator

Drag the Mario Party Netplay GC-Wii folder out of the download and keep it wherever you like. You can launch it using Dolphin.exe after placing your ISOs in the included Games folder.

GCN
Go to Controllers. Under GameCube Controllers, select your controller from the drop-down menu next to Port 1. click Configure to the right of the drop-down menu and configure your controls to suit your needs.

Wii
Go to Controllers. After marking Emulate the Wii's Bluetooth adapter, select your controller from the drop-down menu next to Wii Remote 1. click Configure to the right of the drop-down menu and configure your controls to suit your needs.
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Netplay Usage Guide
Step 1: Accessing Netplay

Launch Dolphin.exe.

Wii
Everyone needs to choose which player they'd like to be and configure their controls in that Wii Remote slot. All players must use a different slot.
Each player must set as many Wii Remote slots to Emulated Wiimote as there are players, and must click Configure > Clear on all ports besides their own.

From here, go to Tools > Start NetPlay.
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Step 2: Connecting to Other Players

If you are joining someone's lobby, the host should provide you their lobby's host code.
If you plan to host your own lobby for others to join, pick the Host tab and double-click the game you want to host. Click Copy next to the room ID and give it to the players who will join you.
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Step 3: Setting up the Game

Wii
Host: Open Assign Controllers/Wiimotes from the netplay window and set each player to the player order decided in Step 3 of the Netplay Setup Guide.


Once everyone is together, the host may start the party using Start. In case of crashing or desync, make sure settings are shared and restart.
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Other Notes

Every player must have the same save file for saving to work. Be sure to run Replace.bat from the emulator's folder to replace the saves before every party you play.

Player order is decided by the order of the netplay room by default. The host can change controller ports in the netplay window.

It's possible for multiple people to play from the same computer as long as the controllers they're using are plugged in and the host allows them use of multiple ports.

It's possible to host a room for 4 other people as long as the host disables their controller in Dolphin.

Lag is an unfortunate but necessary part of netplay. The host may use the Buffer command to increase input buffer and make the game smoother.

If a save file is corrupted, try formatting the data or redownloading the saves.

Possible desyncs aren't always truly desyncs, keep playing to make sure if there was truly a desync before restarting.

Direct connect may be used even when the traversal server is down, and for players who have trouble with the traversal server at all times it may be the only way to play. Forward a port if the traversal server isn't working for you.
Frequently Asked Questions

I already have Dolphin, do I need to download it again?
>Yes. This guide provides a version of this emulator geared specifically for netplay, and it's incompatible with other versions.

How can I reduce netplay lag?
>1) Increase buffer
>2) Close any other programs using internet (web browsers, skype)
>3) Make sure no one on the same network is using the internet (family, roommates)
>4) Seek out players from nearby regions
>5) Ensure it's actually netplay lag by having each player test FPS locally

The game's graphics are bad! Can I make them look better?
>The resolution and anti-aliasing of a game can be changed without issue, though it is not recommended as the emulation will require more resources. If you'd like to edit these options, load a splitscreen Mini-Game such as MP6's Circuit Maximus offline and confirm the game speed does not decrease.

How do I use the GameCube Mic accessory over netplay?
>Mic compatibility is currently not possible over netplay.

How do I play Mario Party 7's Deluxe Cruise mode over netplay?
>8-player netplay is currently not possible over netplay.

I'd like to continue a party using someone else's save, how do I replace saves manually?
GCN
>Have the player whose save you want to use upload their MPN-A.USA.raw file, then download it and stick it in Mario Party Netplay GC-Wii > User > GC.
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Troubleshooting

Whenever I try to join someone's traversal lobby, Dolphin just stalls and I can't connect!
>Depending on how your network is configured, you may only be able to connect to lobbies hosted over Direct Connect. Either have the player unable to connect host the traversal lobby themselves or have the host forward a port and host over Direct Connect. If you need help forwarding a port, try following this guide.


I was playing Mario Party and the board went black! How do I restore it?
>In-game, quit out of the party and try again. If you've been saving every turn, no progress will be lost.


I started emulation in a netplay lobby, but the game showed up as a black screen!
>The black screen is caused by players not starting emulation at the same time. Ensure that no one in the lobby is running the game before the host starts netplay.

Someone desynced on frame 0!
>A frame 0 desync means that there's a checksum mismatch. All players should have the same game version.

I tried both running Replace.bat and replacing a save manually but the save still isn't getting replaced in-game!
>Pathing issues may arise from moving folders around or dragging the emulator folder instead of extracting it. In these cases, the best solution it to redownload the emulator and try again.

How do I solve the error The program can't start because MSVCP140.dll is missing from your computer.?
>Download https://www.microsoft.com/en-us/download/details.aspx?id=48145 and run the file.

Bonus
A few codes that may improve your experience (note that everyone must use the same codes): http://pastebin.com/raw/Bj94N9EX