MidpSSH | SSH and Telnet client for Mobile Devices

Some telcos have firewalls on their network that prevent you from connecting to some network ports. Sometimes they will firewall out all network ports save a few that they leave open.

You may have a firewall problem is you experience or see the following:

• A Connecting message appears when you try to connect but you never see the OK after it

You can help confirm whether there is a firewall in operation by trying to Telnet to an SMTP server, as SMTP ports will often be left open. If that works but SSH doesn’t then a firewall problem is likely. If that also doesn’t work then it’s not so conclusive, but it suggests that maybe there’s a different problem. Perhaps try telnet to a POP box (port 110) as well.

You could enquire with your telco to confirm that they are firewalling, and perhaps discover options - maybe there is a different plan you can be on where they don’t. More likely you may find out which ports they allow or restrict. Otherwise you’ll have to guess.

The workaround is to run your SSH server on a different port; a port that is permitted by your telco’s firewall. So first you need to learn which ports are allowed:

• Asking them is the easiest way to find out open ports;
• But you could also try testing different ports. Try services that would make sense to be open such as SMTP on port 25, HTTP on port 80, POP3 on port 110, HTTPS on port 443. Then try some random ports over 1024. Note: Some devices won’t allow you to connect to HTTP/S ports with a socket connection (see Device Security).