Firefox starts a server on port 1900

I observed this kind of packets being filtered in my place:

Mar 17 13:13:21 reserved kernel: [15070.046566] UDP/OUT: IN= OUT=eth1 SRC= DST= LEN=122 TOS=0x00 PREC=0x00 TTL=1 ID=17655 DF PROTO=UDP SPT=1900 DPT=1900 LEN=102

And for just one moment, because it starts and stops very quickly i found this:

root@reserved:~# netstat --listen -np
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
udp        0      0  *                           5615/firefox

To disable this go to about:config and then set

loop.enabled -> false
loop.rooms.enabled -> false

Good luck.