This post is designed for people who want to share a simple USB printer, such as this receipt printer, over the network.

Usually, you just connect up the printer to the computer like this:

But if you are sending the print jobs from a central server, you would instead follow these steps, and hook up a Raspberry Pi near the printer to pass on the print-outs for you:

This post will show you a very fuss-free way to do this. Because of its simplicity, if you have multiple computers printing (read: you need a server that can spool), or need two-way communication with the printer, then this setup will not be sufficient for your use case.

One-off setup

If your printer is /dev/usb/lp0, then the command to run is:

nohup nc -klp 9100 > /dev/usb/lp0 2> /dev/null&

There is quite a lot going on in this command, so I’m going to break it down into parts and explain what each one does.

nohup

Lets the command keep running after you log out.

nc -klp 9100

Listens on port 9100 (-lp), and returns to listening after each connection (-k)

> /dev/usb/lp0

Redirects any incoming data to the printer device

2> /dev/null

Suppresses errors by sending them to /dev/null

&

Runs the command in the background so that you can keep using the terminal.

Run every boot

Simply schedule the command in cron as a @reboot task.

crontab -e

And add the line:

@reboot nohup nc -klp 9100 > /dev/usb/lp0 2> /dev/null&

Note that if you reboot the printer, you will also need to reboot the raspberry pi to get it to reconnect without logging in!

Send some tests

From a computer somewhere else on the network, send a test print-out:

echo "Hello world" | nc 10.x.x.x 9100

If the target printer is a thermal receipt printer, then you could also use mike42/escpos-php to send it more elaborate commands:

<?php
$fp = fsockopen("10.x.x.x", 9100);
/* Print a "Hello world" receipt" */
$printer = new Escpos($fp);
$printer -> text("Hello World!\n");
$printer -> cut();
fclose($fp);