I have hacked into a mainframe server, and having cracked both encryptions and successfully bypassing the security (except the monitor), I just get an error saying 'Host not responding'.

Why?

you're a victim of the gateway security system. go read the article on the uplink laboratories research centre.

I've now got as far as having the PCForce thingy, but all I see is a string of characters for read which appears to serve no purpose.

What do I do now?

(I've already tried injecting and get told I need read access)

It would serve you well to search the store for useable things.

http://onlink-mod.net/Onlink.0.1.2.001.png

Also, you only need read access. You don't need to do what I'm doing in that image.