java.io.IOException: Bad packet id XYZ

[Neeneko]

I am assuming this isn't a 'bug' per say, but I was wondering if someone could give me some guesses.

There is a server that I connect to that I seem to get a lot of these errors from. The packet ids are all over the place (including vanilla block ids as far as I can tell). Some people on the server also seem to have issues, but others do not.

I was wondering if someone could point me in the right direction regarding this error, or at least give me a summary of what it means. Is it likely to be something messed up on my client or is it a server issue?

This is more for the sake of curiosity then anything else, I figure I can't do much about it, but it is a mystery that I would love to know what is going on

Thanks all.

[pantong]

When I made a server with custom mods. I messed up and installed the same mod into the mod folder and into the. Jar. When launching the server I had that error. Basicly 2 mods sending the same I'd packet to the client. I'm no server expert. But I'm guessing they have extra mods installed with a custom configuration diffrent than yours. Not sure

[Neeneko]

Interesting.

Since it happens erratically, I wonder if some mod is confused or grabbing IDs dynamicly....

[poxun]

I was having this problem. It turned out it was a recent update to my cable modem's firmware by my ISP (Virgin Media in the UK).

In 'router mode' it was somehow corrupting some Minecraft packets. I suspect it is a bug/issue with the adult filter stuff they added with the update even though it is actually turned off. Or maybe they made other changes... their help desk is outsourced overseas is not very helpful.

This would only happen sometimes on connection and if I was able to stay connected for the the first 30 seconds or so I would then be able to stay connected for a long time. If nothing much was happening at login (no items in pipes/machines running etc) the connection was more likely to be stable.

I switched it to 'modem mode' and used an old router I had from before and the errors went away.

Edit: Meant to add... So it may be a networking issue near the server causing some to have issues and others not or if all the users that are having problems are with the same ISP it could be them.