Hello there. I have an isue with my linux server. When i am in my network at the office, where my linux server is intalled i can access it with telnet using the public ip address. But when am at home i try to access it form there i can't. What can be the problem?

well most likely the telnet port on the external interface is blocked by a firewall of some sort. This is a good thing, you really don't want telnet running on an external port (I would advise against using it internally as well).

You best bet is to set up SSH (there is a good chance it is already installed and probably just needs to be enabled.

You may still have to check the firewall to see if will allow incoming connection to the ssh port (port 22 is the standard ssh port). You can also run ssh internally to keep things consistent.

Sutekh is right, disable telnet, not to use it ever...
I have a putty ssh client (for Windows clients) at hand to access the machine.

Does your Linux server have a public IP address (ie, not in the ranges: 10.x.x.x, 172.16.x.x to 172.32.x.x, or 192.168.x.x) ?
If so, it's a matter of firewalling.. If it DOES have such IP, it has a private IP, which is not accessible through the Internet.

To gain access to such server, having a private address, the firewall (or: gateway) granting internet access (read: the router having the non-private internet address) should 'forward' port 22 (the ssh port) to your machine. This is, of course, to be done by the network administrator, if that isn't you.

Cheers,