can a ISP block ftp port 21???

[AndyD]

what are the chances that my ISP is blocking this port? i read on this that they can. i tried everything...even connecting the pc directly to modem didnt help. says that the port is locked up.

http://linksysftp.dyndns.org/troubleshooting.html

[Rudy]

could be ur ISP or Windows

[Qarth]

Well... Your ISP aren't the ones who can give access to ports on machines and such. 21 is used for telnet and ftp. if the host machine doesn't have the protocol or your machine doesn't it won't work. Firewalls and such will conflict also.

[AndyD]

well thats the thing...i tried running the server on another pc without router and without a firewall installed and yet it still says its locked up.

i didnt think it was possible...just trying to verify what the guy from that link said and try to figure out my problem.

[Kenno]

Go to this page:

https://grc.com/x/ne.dll?bh0bkyd2

and click on "Probe My Port" button. If it says your port 21 is blocked and according to what you described above about your server, it must be that your ISP blocked it.

Fortunately, you can use other port different from 21 for your ftp server.

[Geronimo]

to test it. Open a ftp session to 127.0.0.1 i.e. ftp://127.0.0.1/

from the ftp server. That will tell you if the server is accepting connections on that port. Shoot click on that link with your ftp server to test it out. Then test a machine on your local lan. ftp://XXX.XXX.XXX.XXX X's being the ip of the server. Then take one step back if that works and test from the outside of your firewall, if you cant test yourself goto that grc link.

[Vlad]

No one bothered to give him a direct answer?

Yes, ISP's can (and some do) block incoming traffic on port 21. Many also block other server ports, like HTTP (port 80).

[Noerr]

indeed Vlad:

no problems for ISP to block some ports (2 minute job)

infact most of isps that have xdsl or cable modems would either block server ports, or setup frequent dhcp refreshes

[JerryT]

I don't think it's your ISP. It could be a bug on your box, or some other program that has it locked up. Have you tried running netstat?

I doubt an ISP would block your port 21 (even if they could). One reason for this is that you could change your FTP port number. Port 21 doesn't have to be used. I use port 4660. At any rate, give us your system specs.

I have a couple of ideas on why it's blocked.

Peace