There are two TCP connections between the OneClick and SpectroSERVER process.
One is for requests which uses a random port on the OneClick system to port 14002 on the SpectroSERVER system. If this connection is down, the associated landscape in the OneClick console will be red and the "Connection Status" column for that landscape in the Monitored Landscapes page will show the connection as lost.
The other is for callbacks (async notification of alarms/watches/etc) which uses a random port on the SpectroSERVER system to port 14001 on the OneClick system. The "Heartbeat Received" column in the Monitored Landscape page is there to provide visibility into whether this callback connection is established and working properly. This "heartbeat" is sent from the SpectroSERVER to OneClick every 45 seconds. If this connection is down, you will notice no new alarms or alarm updates to existing alarms in the OneClick console for the associated landscape and the "Heartbeat Received" column for that landscape in the Monitored Landscape page will show the connection as lost.