Is it possible for you, to make method TF_SaveServer check correctness of server? For example, saving server IP such as "1.1" doesn't make sense.
It's not a valid IP address, but it might be a valid hostname. For example, editing /etc/hosts you can make "1.1" resolve to a proper IP address.
That's a long way of saying, the current behavior of TF_SaveServer is correct. It accepts IP addresses and host names.
Would be possible to set some timeout for this? If I request Lease in the GUI while starting app, it is stucked for that time, and then just show error message - it is not very user friendly.
In version 4.0 there will be a 60 second timeout. If no successful communication happens within 60 seconds then the connection to the server is assume to not exist (or not be possible). And it will return a timeout error.