identifier of I/O event that just occurred on the device
true if the handler should be called again on next event occurrence or false if this instance should be unregistered from the SelectDispatcher (this is effectively a server shutdown).
TODO: accept() could be called in a loop in this method, in order to accept as many connections as possible each time the EPOLLIN event fires for the listening socket
I/O event handler
Called from SelectDispatcher during event loop.