Everything is done automaticaly, Presence will detect disconnection as well…
This is a simple code I put in my channels
def join("schedule", _params, socket) do
send(self(), :after_join)
{:ok, socket}
end
def handle_info(:after_join, socket) do
user = socket.assigns.user
{:ok, _} = Presence.track(socket, user.id, %{
username: user.name,
online_at: System.system_time(:second)
})
push(socket, "presence_state", Presence.list(socket))
{:noreply, socket}
end
It does imply the socket is assigned to a user, for this, i extract user from a phoenix token.
You also need a client library supporting Phoenix websocket and channels.
And this library needs to be compliant with the Phoenix version.
