I downloaded the sqldeveloper-17.4.0.355.2349-no-jre.zip file.
The included sql.bat file has some invalid statements (set echo on, two html comments)
After my 5mins trying to fix it all i managed to get was "Listening for transport dt_socket at address: 8000"
I stopped looking any further and just copied the version of sql.bat from 17.3 which seemed to work, but i thought i'd report anyway.