What connection type?
If you’re hooking up a network printer, then you’ll have been given a choice of connections when setting your printer up. But what are the different protocols and which one should you choose if given the choice?
The simplest protocol is AppSocket (also referred to as HP JetDirect). It’s usually used when no other connection is possible, but its simplicity also means it lacks any kind of fine control: eg there’s no queue management so you can’t abort print jobs once they’ve been sent. There’s also no way to find out the printer’s status, making it impossible to discover ink and toner levels, eg.
Next up is LPD, which stands for Line Printer Daemon (also known as LPR, or Line Printer Remote). This does implement queue management, and can tell the difference between different types of data, such as raw text or PostScript information. There’s neither support for remote setup nor management, though, and you can’t query the ink or toner (although these may be provided anyway) and your print jobs can’t be encrypted.
The final protocol – IPP – is the most contemporary and functional. It stands for ‘Internet Printing Protocol’ and is what CUPS uses as the basis for managing both print jobs and queues. It’s the preferred method of communication as you get more feedback from the printer and wield more control over it thanks to its bidirectional nature.