Ho trovato 9666 / tcp per ascoltare su 127.0.0.1 su OS X. Uso la versione 15.3.0
> nmap -sT 127.0.0.1
Starting Nmap 7.01 ( https://nmap.org ) at 2016-03-12 16:57 CET
Stats: 0:00:04 elapsed; 0 hosts completed (1 up), 1 undergoing Connect Scan
Connect Scan Timing: About 56.90% done; ETC: 16:57 (0:00:03 remaining)
Nmap scan report for localhost (127.0.0.1)
Host is up (0.29s latency).
Not shown: 999 closed ports
PORT STATE SERVICE
9666/tcp open unknown
Nmap done: 1 IP address (1 host up) scanned in 8.31 seconds
> lsof -i :9666
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
JavaAppli 73246 leo 149u IPv4 0x49ece38ad86e34a7 0t0 TCP localhost:9666 (LISTEN)
> ps -ef | grep -w 73246
503 73246 1 0 5:07PM ?? 16:23.64 /Users/leo/Applications/JDownloader 2/JDownloader2.app/Contents/MacOS/JavaApplicationStub -afterupdate
Che cos'è? Altri dettagli? Con Google non ho trovato informazioni su questa porta e su Jdownloader.