I use ServerPlayNetworking.canSend in normal server and it work perfectly, but after I install BungeeCord server, it no works.

But I can send packet directly.

Resolved in #3244

Not sure if it may be bungeecord not propagating the registration packet to the client or if it is something on one of bungeecord's reserved channels.

Hmm, I think many of those bridge stuff does not propagate any of the handshake packets.

Also, if bungee consumed the packets, canSend would still update in my original v1 design (it sends minecraft:register if it didn't receive handshake payload). Does it work a while after the connection has established?