Mod incompatibility (Instantly disconnected from server)

[Hlebuw3k]

General Information

ViaVersion dump url (v3.1.0): https://dump.viaversion.com/d209b75d284ad1a6b78053b26af3a9b26d4969643a82d850b2b1a99d4e40c8bc

ViaVersion dump url (snapshot version): https://dump.viaversion.com/328bd513bc6b06cca6393b04e1bc9846f73787f9283949ff3a41533ae283a128

Bug Description

Joining a 1.2.5 vanilla server will instantly disconnect me if either of the following mods are enabled:

• Vivecraft https://modrinth.com/mod/vivecraft
• Carpet TIS Addition https://modrinth.com/mod/carpet-tis-addition (with Carpet Mod https://modrinth.com/mod/carpet)

Game version 1.20.4, Fabric Loader 0.15.7, tested with ViaFabricPlus v3.1.0 and a snapshot version from the actions page.
Tested with no other mods installed other than ViaFabricPlus and either one of the culprits (and Carpet Mod in the case of TIS Addition)
I have also joined the same server with over 100 other mods enabled, only when enabling either of those 2 causes me to get disconnected. I can share the mod list if requested.

Steps to Reproduce

1. Install Minecraft 1.20.4, with Fabric Loader 0.15.7, and ViaFabricPlus 3.1.0
2. Install Carpet TIS Addition https://modrinth.com/mod/carpet-tis-addition (with Carpet Mod as a dependancy, note that Carpet Mod does not cause this issue by itself https://modrinth.com/mod/carpet)
3. OR install Vivecraft instead https://modrinth.com/mod/vivecraft
4. Launch the game, select the correct versions 1.2.4-1.2.5 in the Via menu, then join a 1.2.5 server (I tested it with a local server with default settings, downloaded from https://minecraft.wiki/w/Java_Edition_1.2.5)
5. You will be disconnected almost instantly, with the error message "Disconnected" shown as "lost connection: disconnect.genericReason" in the server console.

Expected Behavior

You should not be disconnected and should be able to enjoy happily playing Minecraft with those mods.

[Hlebuw3k]

ViaProxy can be used to bypass this issue: https://github.com/ViaVersion/ViaProxy but skins do not seem to work, and you can't select the same version as the server in the ViaFabricPlus menu if you are using it. And launching the regular version (not Java 8) gives me an error "Java Virtual Machine Launcher: A Java Exception has occurred." right away and refuses to work.

[FlorianMichael]

Hi, thanks for reporting this issue!
You don't need to share your mod list since it's already included in the ViaVersion dump.

Skins in ViaProxy are broken because you didn't enabled legacy skin loading in the advanced tab, I don't really understand what you mean with the "select same version as the server" part in ViaFabricPlus and the Java 8 version issue is most likely something with your Java installation (if not, you can create an issue on the ViaProxy github page).

To come back to your issue:
Fabric mods are known for breaking ViaFabricPlus/ViaVersion since they are sending modded networking data which is not translated properly by ViaVersion, you can try https://github.com/ViaVersionAddons/ViaVanillaPlus to see if that fixes your issue (It's a mod fixing other mod's networking to work with ViaVersion again), otherwise I would be interested if this issue only appears on <= 1.2.5 servers or if you can also test newer server versions like 1.8, 1.12 or 1.16.5? Sounds like a strange issue to me.

[Hlebuw3k]

Hello again. I did some more testing and found this:

• Connecting to a 1.8.9, or 1.12.2, or 1.16.5 works and I can play on them with both mods installed (Carpet TIS and Vivecraft) and without needing ViaVanillaPlus.
• Connecting to a 1.7.10 server disconnects me instantly without or with ViaVanillaPlus. Sometimes there is around 1 frame of the world loading in, sometimes even the inventory items on the hotbar are visible, but I get disconnected before I can see any blocks.
• Surprisingly, I can connect to (and play on) a 1.0.1 server, with both of the mods (Carpet TIS and Vivecraft) and without needing ViaVanillaPlus.

So considering the tests, this is probably an issue only happening on servers before 1.8.9 but after 1.0.1, and ViaVanillaPlus did not help me solve the problem.

Regarding the "select same version as the server" it is this menu on the multiplayer screen right here:

Older versions require me to select the correct option manually, otherwise the Auto Detect option works just fine.
Here is a version dump of a clean install, with only the required mods, this is what I did the tests with, in case it's needed: https://dump.viaversion.com/4c43145b2c672dcabdaf377c4f4daafe2a744b20238878c039d4b6ff0abc1d7f

Other than that, I won't elaborate on ViaProxy because this is not the GitHub repositry for it.

[HowardZHY]

What server software does the 1.7.10 server use? Forge 1.7.10 servers requires all clients have Forge so unsupported

[FlorianMichael]

@Hlebuw3k Can you provide the server ip and if possible also the software used for the server (like Howard already mentioned Forge for example is not supported)? Otherwise can you try the latest dev build from GitHub actions?

[FlorianMichael]

Also, can you provide your latest.log file where you get the issue so we can search for any errors?

[Hlebuw3k]

As I said before, I used vanilla servers. I downloaded the server files from minecraft.wiki (the official wiki for the game) and ran the servers on my own computer, and connected to localhost. So if you want the server ip, it would be 127.0.0.1 or localhost (or your own computer ip) because I ran the server on my own computer.

The server software can be downloaded form the wiki page of the game version. (on the right side of the page) You can either choose the .jar or the .exe version of the server, the issue is present in both cases. Here is the wiki page for Minecraft Java 1.7.10 https://minecraft.wiki/w/Java_Edition_1.7.10

The first time I got this issue however, when connecting to one of my friends servers, and I'm not comfortable sharing my friends ip. You will have to run your own server or find a server on that version.

Here are the latest.log files when trying to connect to a 1.7.10 vanilla server, while using only the Vivecraft and ViaFabricPlus mods.

Client log: latest.log

Server log: latest.log

Unfortunately the latest dev build from GitHub actions does not fix the issue, and the log files look exactly the same. Here is the client log using the latest dev build just in case: latest.log

[FlorianMichael]

Can this be retested on latest versions (https://modrinth.com/mod/viafabricplus/version/3.3.0)? It might be fixed due to all the networking changes which happend in the meantime.