How printers are discovered on the network and locally

Great news: PaperCut Pocket and Hive do the heavy lifting to discover USB and networked printers in your organization.

Read on to find out how PaperCut Pocket and Hive find your printers, help organize them, and publish them seamlessly to your users.

The printer discovery process in a nutshell

The printer discovery process is part of the edge node component. It starts automatically when a sysadmin installs PaperCut Hive or Pocket for the first time.

Here’s a summary of the printer discovery process:

1. Scan - The scanner finds things that look like printers on the network or on locally connected printers on your computer.
2. Probe - The probe follows behind the scanner and when something’s found, checks what kind of printer it is, as well as what it’s capable of (for example, does it have a duplexing unit?).
3. Validate - Details from the probe are checked and printers are further interrogated and verified.
4. Report - Details about the newly found and verified printer are sent to the cloud.

In the cloud, the printer details are stored in the Printer Registry . This is the ‘printer database in the sky’. It keeps track of which printers are associated with a specific organization, as well as all the capabilities and properties of the printers.

Scan - Are there any printers out there?

The scanner’s primary responsibility is to identify sources that look like printers on the computer (Windows or macOS queues) - or somewhere on the network. There are two types of scanning: local queue scanning and network scanning.

Local queue scanning

The local queue scanner talks to CUPS (on macOS or Linux) or the Print Spooler (on Windows) to get information about locally configured print queues. The local queue scanner also moonlights as the ‘probe’ for local queue information.

Network scanning

The network scanner starts by picking up clues from local print queues to prioritize which network addresses to scan. It then scans the network for devices that look like printers. When it finds something, it uses SNMP queries to check that the device found is actually a printer, and if so, what type of printer.

Probe - What printer details are available?

The probe uses SNMP and IPP to collect as much data as possible about the printer candidates that the scanner found. The probe isn’t too picky or judgemental about what it finds - all it’s doing is gathering as much information as possible to hand over to the validator.

Validate - Is it definitely a printer?

The validator uses SNMP or IPP requests to further validate the previous findings, and to gather capabilities of the printer. Can it do 2-sided prints? Is it out of toner?

For network printers, the validator needs to be able to retrieve at least an IP address, MAC address, and make or model of the printer before it can say ‘yes this is a printer’. If it’s definitely a printer, it reports it to the cloud.

For locally configured queues on the edge node, the validator looks for the ConnectionURI (the connection string) in the local queue configuration (for example, CUPS).

Report - Tell the cloud about the printers

The reporter sends the printer candidate (and all the additional SNMP or IPP data found) to the printer registry in the cloud. It’s worth repeating here that everything sent to the cloud - no matter how ‘innocent’ - is encrypted and sent over secure protocols. In this case, HTTPS.

Printer Registry - Making sense of all the printer data

The Printer Registry receives the printer candidate requests and starts putting together a ‘definition’ for each of the printers. This definition includes the printer’s:

• location (including the IP address for network printers, or which machine it’s connected to for a locally-attached printer)
• make and model
• capabilities.

From this information, it starts to build a big picture of the printer landscape.

It also creates a coordinator map, detailing which edge nodes have access to which printers. This is especially important for local printers (for example USB printers) - you can’t print to a USB printer unless you’re sending the job from the computer it’s plugged into! However, it’s also important for network printers - organizations might have VLANs and other networking obstacles in place, which means that some printers are only accessible from certain computers.

If the Print Registry doesn’t have enough information about a printer to build a genuine printer definition, it filters that printer out. It also applies filtering to printers that shouldn’t be registered, like PDF queues (Virtual printers), fax queues, test printers, PaperCut MF monitored print queues, and PaperCut Mobility Print URIs.

Deduplication/printer matching

The printer matching algorithm finds matches for already-known printers. It looks at qualities such as IP addresses, ConnectionURIs, MAC addresses, hostnames, and serial numbers. If there are enough details to consider the printer is a match, the printer will automatically get updated with any new incoming information.

For example, you’ve moved the printer’s IP address to a different location in your office. The printer will match against its MAC address, ConnectionURI & serial number. However, we detect that it has a new IP address. The IP address will get updated accordingly.

Printer registration

If the Printer Registry doesn’t find a match, it registers the device as a new printer. It chooses a new name for the device based on the metadata it received.

Ongoing printer discovery

For the first 24 hours after signing up, all your printers are found and published automatically.

After all printers are discovered for the first time, the edge node continues to scan and look for new printers. You can turn scanning off if you like in Easy Print & Scan > Auto Printer Discovery.

When it discovers a new printer, it adds it to the Newly Discovered printers list.

There are three options for what to do with the newly discovered printer:

• Review it and add it to the Printers list.
• Review it and update an existing printer with the new information.
• Add it to the Ignored list.

The options are described below. For steps on how to do each option, go to Managing (adding, removing, publishing, unpublishing) printers. 

Add a printer to the Printer list

Do this when, for example, you know that you’ve just received the new printer in the office and you need all of your users to be able to print to it.

Update an existing printer

Sometimes printers send incomplete information. If you think the printer looks familiar to an existing printer, you can choose to update the existing printer, essentially merging the existing printer to the new printer. The new printer will inherit all of its existing printers setup such as:

• printer labels
• printer apps
• PrinterId (used for troubleshooting)
• print queues on edge nodes (make sure your queues on compatible!).

Ignore a printer

This adds the printer to the Ignored list. It won’t be monitored anymore and no jobs (print, copy, fax, or scan) will be tracked. You can always move it back to the Printers list if need be.

Printer discovery frequently asked questions (FAQs)