Synergy 2 only woking with VPN active

[betafusion 1]

At my workplace, internet connectivity is provided by a campus-wide service which limits outside connections to a few select serviced (ports), i.e. I can only access some standard ports like 80 and 443 on an external server. Internal connectivity (our company intranet) is handled by us and not restricted in any way.

I cannot get Synergy 2 to run in this configuration, as it seems to try to access a cloud server on a blocked port. I am getting error messages like:

[ Config ] [2017-10-10T11:21:03] DEBUG: requesting profile snapshot
[ Service ] [2017-10-10T11:21:03] debug: connecting websocket
[ Service ] [2017-10-10T11:21:03] error: can't send profile snapshot, not yet received from cloud
[ Config ] [2017-10-10T11:21:03] DEBUG: Profile ID: 5184 name: default
[ Service ] [2017-10-10T11:22:36] debug: tcp client connect error: Ein Verbindungsversuch ist fehlgeschlagen, da die Gegenstelle nach einer bestimmten Zeitspanne nicht richtig reagiert hat, oder die hergestellte Verbindung war fehlerhaft, da der verbundene Host nicht reagiert hat
[ Service ] [2017-10-10T11:22:36] debug: websocket connect failed
[ Service ] [2017-10-10T11:22:36] debug: retrying websocket connection in 3s
[ Service ] [2017-10-10T11:22:39] debug: retrying websocket connection now
[ Service ] [2017-10-10T11:22:39] debug: connecting websocket

The tcp client connect error message is  german for a timeout error.

As soon as I use a VPN on both computers (in my case VyprVPN), Synergy 2 starts working, presumably because the cloud stuff now correctly works. I don't think that behavior is intended, is it?