This post was originally written by Kiriyashiki, who renamed their GitHub account. I have decided to repost this, since the information in this post is very helpful and I wasn't able to find the new name right away. Credit therefore goes to https://github.com/Kiriyashiki . I (Gab) have also tweaked this post with further information. Also thanks to Hi5Glaceon_ for helping with some edits in this guide!
The 86420 error code is often due to improperly configured networks blocking the P2P connections when going online. Multiple things can cause this, mainly bad NAT or firewalling.
This guide will go through several ways to fix this error. Is it recommended to apply both fixes for minimize the chance of running onto this annoying error. Let's get started. Even if you're not familiar with PCs, this guide will help you fix the error.
Firewalls may block incoming connections to Dolphin. To fix this, we need to allow Dolphin to bypass the firewall.
Open the Windows Firewall configuration screen:
Unwrap the list on the left, and select Inbound rules. Right click it and select New rule.
- Rule type: Program
- Program: Select your Dolphin.exe
- Action: Allow the connection
- Profile: Select all
- Name: Whatever you want!
Repeat the same for Outbound rules. Now, the firewall should be properly allow connections to Dolphin.
Look through your Outbound and Inbound rules to make sure, that there's no rule that blocks Dolphin.exe - alternatively: Rename the folder of your Dolphin install and try again. This way, Windows Firewall treats it as another program. (If you're using Wheel Wizard, you need to change your Dolphin executable path too.)
Use either of these commands to allow the ports. Note that this will not only open the firewall for those ports on Dolphin but on your PC entirely. Use with caution.
- UFW:
sudo ufw allow 6500&sudo ufw allow <YourPortFoundBelow> - IPTables:
iptables -A INPUT -m multiport --dports 6500,<YourPortFoundBelow> -j ACCEPT
If you have access to your router access panel, make sure your NAT type isn't too restrictive. If you 100% know that it isn't, you can skip this step. If you don't know what your or a NAT type is, don't skip this step!
Windows users can use the NAT tester by Hi5Glaceon_.
If you feel comfortable downloading another executable (.exe file), download the STUN version: https://github.com/GABRlEL/nat-tester/releases/download/prod-v2/STUNv2.zip
If you don't feel comfortable or can't download another EXE, use the Teredo version: https://github.com/GABRlEL/nat-tester/releases/download/prod-v2/Teredov2.zip
Note: The Teredo version isn't as reliable, so using the STUN version is recommended!
Download the STUN version linked above & extract the ZIP! Now download the STUN executable set: https://www.stunprotocol.org/stunserver_win64_1_2_16.zip & extract the ZIP!
Now merge the folder contents, so that the .ps1 scripts and executables are in the same folder.
Hold shift and right click somewhere in the folder with the scripts and executables, while not clicking on a file. Now open a PowerShell window.
Now type .\NAT-Type-Test-Launcher_DEU.ps1 for German or NAT-Type-Test-Launcher_ENG.ps1 for English. The script will now guide you through.
If you get smart screen warnings, always disregard the warnings and press options like "Open anyways". Alternatively, right-click the script, open Properties and check the "Allow" checkbox at the bottom.
If the result is Restricted or Symmetric, you can try port forwarding anyways - but your chances aren't good. You'll likely need to get in touch with your internet service provider/mobile carrier to get this solved.
Some router may have a Teredo filter. If you have issues using this script, make sure that your router isn't blocking Teredo packets.
Download the Teredo version linked above & extract the ZIP!
Hold shift and right click somewhere in the folder with the scripts, while not clicking on a file. Now open a PowerShell window.
Now type .\Teredo_State_DEU.ps1 for German or .\Teredo_State_ENG.ps1 for English. The script will now guide you through.
If you get smart screen warnings, always disregard the warnings and press options like "Open anyways". Alternatively, right-click the script, open Properties and check the "Allow" checkbox at the bottom.
If the result is Restricted or Symmetric, you can try port forwarding anyways - but your chances aren't good. You'll likely need to get in touch with your internet service provider/mobile carrier to get this solved.
If you're not on Windows, you can use the website below. The site is not 100% reliable though!
Go to https://ip.bieringer.net/cgn-test.html?redirect=1
Press "Test supported protocols" > then "Start initial test" > then change the number left to 1024 > then "Start normal test". This test can take a few minutes to complete.
Now check the Histogram and 2D Source Port distribution. If you see yellow/red dots/lines, you are probably behind a CGNAT. If you only see Green, then you're likely not.
If you're behind a CGNAT, you can try port forwarding anyways - but your chances aren't good. You'll likely need to get in touch with your internet service provider/mobile carrier to get this solved.
You now made sure that port forwarding is even an option. You need access to your router configuration panel, which usually means you need a password. If you can't access this, because the router owner won't let you or your WiFi is managed by your school/company, you can't traditionally port forward! If you have access to your router configuration panel, you can skip this step!
If you cannot access your router's configuration, you should try using UPnP IGD. For this, you can use this tool: https://www.xldevelopment.net/upnpwiz.php (windows)
Install, and launch it. Select the local IP that you use to connect to your router. If there are multiple, try each one, clicking the refresh button. If nothing shows up after trying all, your router does not support UPnP IGD, so you cannot use this method.
If it works, you should have a list (that may be empty, but) that will say UPnP device: <router model>.
Work through the guide, at III.2 - Forwarding you can then refer to Method 2.
Now we need to make sure that the port Dolphin uses is forwarded to the Internet. We need to identify which port Dolphin uses first. The port MKWii uses is in the range 22000-22999 and depends on the last 3 digits of the serial your NAND. If you use an imported NAND from your Wii, your serial should be easy to find on the console, so you can skip II.1. If you don't know the serial of your NAND, then here's how to find the correct port:
Firstly, open Dolphin and launch Retro Rewind, then connect to Retro WFC. Do not close Dolphin yet, just stay in the online menu for now, and make sure you do not get disconnected.
Next, open the Task Manager. Right click the row where it says CPU, Memory, ..., and check on PID. Scroll down to Dolphin and take note of the number under PID.
Open a terminal - any will do (cmd, powershell, ...)
Type the following command and press Enter: netstat -ano
This command will list your ongoing network connections on your computer, including Dolphin!
Scroll down to UDP. Find listings with the PID number you noted earlier - typically, there is two: 0.0.0.0:6500 and 0.0.0.0:22xxx.
In my case, the port is 22427! Take note of yours.
Now, close Dolphin.
We have found the right port, now let's forward it!
To check your serial, there's two methods - using the /setting command on the Retro WFC Discord Bot or the NAPT web version.
You can find your setting.txt at Dolphin Emulator\Wii\title\00000001\00000002\data\setting.txt. The Dolphin Emulator folder can be found in either Documents, %appdata% or in the User folder of your Dolphin install when using portable.
Don't share this file or any information in it with anyone except moderation.
Both tools will tell you your SERNO. The last 3 digits of your SERNO will tell you the port you need to forward.
In this case, my serial ends in 427, so doing 22+427 tells me, that I need to forward port 22427.
Now, port forwarding time!
You will need your router local IP. To find it, open a terminal like earlier, and type: ipconfig
This will list your interfaces. Look for the one you are using to connect to the Internet (likely WiFi or Ethernet)
Look for Default Gateway.
Open this address on your browser - in my case I'd open http://192.168.1.1.
You have found your router's configuration panel. From there, you need to set up forwarding for the port number you found earlier and port 6500. If you face the error 84020, you need to forward 27900 & 27901.
In my case, I am forwarding 22427 and 6500 from my computer.
Now you may be asking to how to do that. The issue is that it depends on your router model - and probably ISP as well. There is not really an universal way to do it.
You should search online "How to port forward on 「router model」". Here is a general explanation: https://www.wikihow.com/Set-Up-Port-Forwarding-on-a-Router
Download this tool: https://www.xldevelopment.net/upnpwiz.php (windows)
Install, and launch it. Select the local IP that you use to connect to your router.
If there are multiple, try each one, clicking the refresh button.
Now, like earlier above, you should have a list (that may be empty, but) that will say UPnP device: <router model>
You can then click '+' to add a mapping.
Input your port, and make sure to select the right local IP, with protocol UDP.
In my case, I am forwarding 22427 and 6500. If you face the error 84020, you need to forward 27900 & 27901.
In 'lease duration', you can set the amount of time in seconds the rule will stay if you want it to be temporary, or else leave 0 for permanent.
If you have correctly set up the two fixes, you should almost never run into this issue anymore. If it still happens right after doing the fixes, restart Dolphin and/or disconnect and reconnect your Internet. If you still have issues, you may have done something wrong. Try verifying that you did everything correctly.
If you are somehow still stuck, that's really unfortunate, but there is still a few things you can try :
- Try Mobile Hotspot: With your phone connected to 4G/5G, enable a wireless or wired (USB tethering) to your computer.
- 「NOT RECOMMENDED」 Enable DMZ for your computer in your router config. BE CAREFUL, THIS MAY PUT YOUR COMPUTER AT RISK OF AN EXTERNAL ATTACK. ONLY DO SO IF YOU ARE FULLY AWARE OF WHAT THE DMZ DOES EXACTLY.
- Contact your internet service provider / mobile carrier to get a less restrictive NAT.
- Worst case: Get a VPN (server). On Retro WFC specifically, it has to be with a static IP. You're required to open a RWFC ticket on the Discord to get it whitelisted. It's important that the IP is static and exclusive to you, to prevent abuse.
I hope this guide has helped you steer clear of 86420 (& 84020) errors, have a good day!