I am trying to run an ftp server app on my galaxy s4 (tmobile) and it starts ok, binds to the wifi address and port 8021, but then I can't connect to it. I tried pinging my internal ip address as well and it's not responding. I also tried running nmap on it and it says All 1000 scanned ports on are filtered. I haven't been able to find any settings or anything - any idea what could be blocking the ports? I have checked the IP both via a ip info sort of app, as well as through my router's connected devices page. Any ideas?

Update: I just tried a different FTP app just to make sure and same thing.

Update: Here's my nmap output:

$ nmap -Pn -p 8021

Starting Nmap 6.00 ( http://nmap.org ) at 2013-06-08 17:21 EDT
Nmap scan report for
Host is up.
8021/tcp filtered ftp-proxy

$ nmap -Pn

Starting Nmap 6.00 ( http://nmap.org ) at 2013-06-08 17:23 EDT
Nmap scan report for
Host is up (0.066s latency).
All 1000 scanned ports on are filtered

Nmap done: 1 IP address (1 host up) scanned in 14.77 seco

I am trying to connect to the phone from my windows box via filezilla and running the nmap from my raspberry pi, again on the same wifi network.

I also checked the router's connected devices and the IP address there matches what the phone shows.


  • Running FTP servers on default port like 21 didn't seem to work for me.. Try running the ftp service on something like 2121..
    – Irfan
    Jun 8, 2013 at 6:44
  • Running FTP servers on any port below 1024 will require root -- so if the device is not rooted, the service is not offering anything on that port (it simply can't). I would also check if the router somehow firewalls your connections.
    – Izzy
    Jun 8, 2013 at 11:37
  • Ah, good point, but unfortunately that's not it - I am using a 8821
    – naumcho
    Jun 8, 2013 at 15:12
  • @Izzy my router doesn't filter anything
    – naumcho
    Jun 8, 2013 at 19:37
  • 1
    OK, so one candidate filtered out. May I suggest you to edit your question and include those details (port used, filter checked, port range checked ("all 1000": from port..to port? Including the port you've configured for your FTP server?)). I further assume being the IP of your SGS4, and nmap was used from within the same network (e.g. a machine with IP 192.168.1.* connected to the same router)? Clear facts help finding good answers :)
    – Izzy
    Jun 8, 2013 at 19:50

1 Answer 1


This turned out to be a problem with my router - earlier today I also noticed that I couldn't connect to my printer either - it seems like the router had gotten in a weird AP isolation mode or something like that somehow - I rebooted it and I can connect to the S4 as expected now.

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