You can also do this via "netcat", running the commands below in a terminal.

Receiver (listening to port 31337):

`nc -l -p 31337`

Sender (connecting to receiver IP):

`nc <receiver_ip> 31337`

Want to send a message to the receiver:

`echo "Hello from Kocial" | nc <receiver_ip> 31337`

== if you want to send a file ==

Receiver:

`nc -l -p 31337 > hackernews.pdf`

Sender:

`nc <receiver_ip> 313337 < hackernews.pdf`

This doesn't punch through NATs at all, which is the point of Dumb Pipe