Why does JDownloader use 9666/tcp on localhost?

Question

I found 9666/tcp to listen on 127.0.0.1 on OS X. I use version 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

What's that? Any more details? With Google I found no info about this port and Jdownloader.

Answer 1

Basically it's a port JDownloader is listening to to make browser integration easier (aka you can add an extension to your favorite browser which then passes URLs to JDownloader for downloading).

Some details about this Flashgot interface can be found here.