Hello,
I am currently developing my HA setup in a VM on my desktop PC. The PC goes to sleep when not used.
While the LCN connection is correctly established after a fresh HA server start, it remains disconnected when the PC wakes up from standby. I am aware that it a server going to sleep is not the standard usage pattern, yet it would be nice to have the LCN integration check for wake-up events and reestablish the connection automatically.
Is this something that could be added?
It is not your VM that goes to sleep, but your hypervisor.
The VM probably might not even know the hypervisor was sleeping.
Yeah, don’t be too picky on semantics. 
For comparison: the Reolink integration restablishes the connections to the cameras upon wake-up.
integrations might reestablish connections, but it is based on detecting the connection as being lost, not start events of the VM or hypervisor.
The problem with this setup is that it is dependent on how the devices communicate.
If it is a push setup, then the server might just sit and wait for messages, but the clients gave up sending when the server was in sleep, so nothing happens.
Even if there is a “heartbeat” ping, then there have to be a timeout on that ping, before it can be considered lost and then it is unknown if it was lost in the network or at the other end, so multiple of these have to be lost before it is considered dead. This is just the way TCP/IP networks work.
Timeouts of 10-15 minutes before giving up is not uncommon in TCP/IP networks.