Установив nmap, имею:
# nmap 127.0.0.1 -p 4200
Starting Nmap 7.01 ( https://nmap.org ) at 2017-03-04 19:32 EET
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000056s latency).
PORT STATE SERVICE
4200/tcp open vrml-multi-use
Nmap done: 1 IP address (1 host up) scanned in 0.30 seconds
А куда дальше? Можно ссылочку на описание?