Why is my Minecraft server sending so many packets?

Solution 1:

I found out what the issue was. It was me using a custom datapack race for the Origins mod.

For people who might end up in this thread in the future because of high network traffic with minecraft:

For diagnostics, I used Wireshark, and NetLimiter 4.0, but any programs should do that are able to monitor your network/packet traffic.

I suggest you try to isolate the issue as much as possible. For me, I knew the issue was with me, because the network traffic only spiked when I joined, not when others.

I ran a barebone minecraft server on the same version as the modpack (for me 1.16.5) to see if the issue was related to the modpack, or if it occurs in vanilla minecraft too, thus further isolating the problem. It was only with the modpack. After this it clicked, that the issue could be with my custom race that I added to the Origins mod, but if your case is different, or for any reason doesn't apply here, the next step I'd do is temporarily moving my player file out of the server, so when you join back into the game, the server generates a completely new player file for you. This is useful, because your previous player file might be "corrupted" by mods, or just bugs in general, just so it doesn't crash the game, but it creates large amounts of traffic. (keep in mind, this resets everything about your in game character, things like your inventory, level will be deleted.)

As previously mentioned in the comments by the user SF. Xrays, or other cheats massively increase the amount of network traffic. So if you use anything like those, I'd suggest trying to disable them first.

Hope this helps anyone else, having similar problems in the future! :)