Finding out the printer url for hpaio scanners

Run the following command:

 sudo hp-setup -i <printer ip address>

Among other things the resulting output will contain a line similar to this:

Setting up device: hp:/net/Deskjet_3050A_J611_series?ip=192.168.1.116

You can then replace the hp: prefix with hpaio: and call simple-scan like so:

simple-scan hpaio:/net/Deskjet_3050A_J611_series?ip=192.168.1.116