Grsync is a simple frontend to rsync tool. It comes with many rsync options but nothing about ssh.
I’ve found the solution in this thread. It’s pretty easy and obvious once one knows.
In the source or destination, enter :
firstname.lastname@example.org:/remote/path/ # where xxx.xxx.xxx.xxx is an IP adress
Note : if the remote user is the same as your local user you can enter only the hostname or ip before the path like this:
Then, we need to tell rsync to use ssh, and because this option is not in Grsync, we’ll use the Additional Options text entry on the Advanced Options tab. Type in this :