Connect on-premise gateway to MySQL database on Azure linux vm via ssh

Hello!

We have the challenge that our MySQL database is hosted in azure on a 

linux vm. It is only reachable via ssh. Via mysql workbench we can connect to it.

The service however does not seem to like to use ports or similar.

I am personally very confident that around Dec 2017 this worked somehow, because

I have a dataset that actually synched with this exact setup.

The error message says that it was not able to connect to the mashup data source.

Our server is like serverurl:3306. Is this wrong? Do I have to add the ssh port somewhere there?