Using Eclipse 2019-09 with the latest compatible ABAP Development Tools (ADT) I am unable to connect to the remote SAP server when opening a new ABAP project. I double checked the server IP, system name and instance ID. When trying to connect there is an error message that says:
Logon to system SYSTEMNAME failed (hostname 'mycomputername' unknown)
When googling the error I find a lot of Unix (especially Mac) users having the same problem. They often suggest to modify the /etc/hosts file. I tried to do the similar thing on Windows (C:\Windows\system32\drivers\etc\hosts) but it didn't help.
The problem was my computer name (which was actually not mycomputername). It contained non ASCII / Unicode characters which was fine for Windows but apparently some DNS or Eclipse network routing failed due to this. Changing my computer name to only ASCII characters and restarting Windows afterwards solved the problem.