Same problem here. I’m unable to connect to home server since it was updated to 1.12.2. No problem with 1.12.1. Same problem with last snapshot (17w47b). I believe (as @paul williams said) that the problem is the change in Minecraft server protocol in 1.12.2 [Changed parameters in Keep Alive (clientbound - 0x1F) and Keep Alive (serverbound - 0x0B) from VarInts to longs.]. I think that in some particular circumstances (bad internet connection for example) this change in Keep Alive protocol causes disconnection. It’s a big annoying problem, since I can’t play online anymore with last stable release. Sorry for my bad english.
_Neon10_
Same problem here. I’m unable to connect to home server since it was updated to 1.12.2. No problem with 1.12.1. Same problem with last snapshot (17w47b). I believe (as @paul williams said) that the problem is the change in Minecraft server protocol in 1.12.2 [Changed parameters in Keep Alive (clientbound - 0x1F) and Keep Alive (serverbound - 0x0B) from VarInts to longs.]. I think that in some particular circumstances (bad internet connection for example) this change in Keep Alive protocol causes disconnection. It’s a big annoying problem, since I can’t play online anymore with last stable release. Sorry for my bad english.