Ask HN : Why my mobile phone carrier is showing me those TCP ports open ?

Hello everybody,

I've been poking around this morning with a network diagnostics app on my Android phone and I got surprising results when I ran a port scan against my servers.

On th 1-1024 range I found my usual 3 open ports (HTTP/HTTPS - SSH [running on non standard port]) and strangely ports 21 (FTP) and 554 (RTSP) open. When I try to telnet into them from the phone I can connect but I never receive any reply.

I know I've got nothing running on those ports and running a netcat from my desktop confirm those ports are closed.

My guess is my phone operator is doing some MITM but why on those 2 specific ports ?

Regards,