You actually can do this with netcat, I believe it is already installed in most cases on linux, and it's dead simple.

On PC 1, type: nc -l 55555

On PC 2, type: nc $IP 55555, where $IP equals the local IP address of PC 1 [e.x. 192.168.2.50]

Once you do this, in the same box, from PC 2, type something and press enter. Then go over and look at PC 1, and your message will be there! It works both ways.

You can also choose a different port than 55555, or if you opened your firewall, you can do this through the internet via your external IP.