Accessing Remote Shells from Android
Accesing public UNIX servers such as SDF, Grex or tilde.town is usually done using a desktop or laptop device. Using a phone or tablet requires a little more effort and raises some extra issues. I have been accessing SDF-EU and tilde.town on various android phones for some years, so I feel I can offer a little advice on this subject.
Making the Connection
The most obvious way linking your device to a remote server is to use a terminal emulator. There are quite a few of these available so it's a good idea to have a look at a few. For some time I used JuiceSSH. Inspite of the name, it can connect using SSH, telnet (not often used these days), mosh (more on that later) and it will even let you access your devices local shell (not very useful unless you have a rooted device). You can create a number of preset connections accessable from a simple list. You can also set up identities, username and password pairs, so that if you can access the same server in different ways. The free version will probably be good enough for some users but paying for the pro version gives you widgets and shortcuts and adds port forwarding. This is a very solid, well developed program that seems to be aimed at people who need access a large number of servers 24/7.