Player-To-Server Connection Detection

[jakj]

I need to do one of the following, whichever ends up being easier/better:

*) On client-side, detect when the player connects to a remote server instead of running the integrated one, and send a packet when the connection has stabilized.

*) On server-side (dedicated or LAN-shared integrated), detect when a player connects, and send a packet when the connection has stabilized.

What are the different methods available for this? I want to do it without any sort of tick handler: I want to respond to actual game or Forge events.

[Lethosos]

Don't event listeners do that already?