Ping function and events

[asfernandes]

fb_ping and Attachment::ping, in the case of tcp/ip connection, only checks the main connection.

When client registers events, I think it should also check the event connection, which may brake while the main one is fine and application could just stop to receive events.

[dyemanov]

I somewhat agree, but I know fb_ping() is also used to monitor response time from the server and checking the events port could slow it down a bit.

[arthurbolsoni]

Is it possible to add a callback to the connection so that it is called when the connection closes?