The LinkStatus can be used inside the nodes to keep track of the link status
It embeds a protobuf LinkStatus message which is cloned each time has to be sent out
The data_in and data_out functions can be called when new data is received or sent
One of the change_state, state_ok, state_failed functions can be called when the link goes up or down.
From time to time the send() can be called to send the data to Yamcs.