Presto Troubleshooting

Comprehensive information to resolve most problems with Presto. Includes links to more detailed solutions.

Table of Contents
Network Requirements
Starting and Stopping the Presto Service
Troubleshooting the Admin UI
Troubleshooting Printing
Troubleshooting Hosts
Troubleshooting Firewall/Antivirus Software
Uninstalling Presto

Note: The contents of this article are specific to Presto Server version 3.0 and later.  If you are running an earlier version of Presto 2, we encourage you to upgrade as soon as possible.  Your purchase of the Presto 2 license entitles you to free upgrades to all Presto 3.0 versions.

Network Requirements

The following are required for various aspects of Presto to properly function:

Whitelist URLs (optional) - Port TCP 443
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Whitelist URLs (Required) - Port TCP 443
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  • TCP 9631 Inbound (file transfer from wireless device to presto server)
  • TCP/UDP 53 Inbound (uDNS)
  • UDP 5335 Inbound (mDNS)

Starting and Stopping the Presto Service

The Presto service can be started and stopped from a command prompt.


Navigate to C:\Program Files\Collobos\Presto\Service and type the appropriate command:
.\prestod64 --stop
.\prestod64 --start


Navigate to /Applications/ and type the appropriate command:
sudo ./prestod --stop
sudo ./prestod --start

Troubleshooting the Admin UI

If the Admin UI fails to load, follow these steps to diagnose the problem: 

If the UI is a black screen:  Please "Allow Outbound Internet Access".

Note: this example uses as the IP address of the Presto Primary Server.

  1. On the Presto Primary Server, go to a command prompt and enter the following command in the format indicated: nslookup
  2. This should return If it does not, it's likely that you have DNS rebinding and that must be whitelisted Please see Network Requirements in this article for more details.
  3. After making necessary corrections, re-enter the above command. If it returns and the Admin UI still fails to load, contact Presto Support.

Troubleshooting Printing

The following steps should resolve most printing related problems.  For more comprehensive information, see our Advanced Troubleshooting guides:

Printers cannot be seen.
  • Check that printer is set to 'Active'. See Printers in Presto Administration.
  • Confirm that the ordering of the DNS servers handed out by DHCP orders internal DNS servers before  See Prepare the Network in How to Install and Configure Presto.
  • Confirm that there aren't one or more Rules causing the problem.  Problems can be caused by a conflict between one or more Rules or by a Rule whose ramifications aren't fully understood.  The following steps can help resolve a Rules-based issue.
    • Ensure the required printers are set to 'Active'.  See Printers in Presto Administration.
    • Turn off all custom Rules. See Rules in Presto Administration.
    • Re-enable a simple printer advertisement rule to confirm the system is advertising printers.  After confirming, turn this generic rule off.
    • Re-write or re-enable a single custom Rule at a time to confirm the logic and result.
  • Confirm mDNS or uDNS advertisement. See Hosts in Presto Administration.
    • mDNS - Select the Host on the subnet and confirm mDNS Advertisement is set to active.
    • uDNS - Confirm the correct conditional forwarding record is pointing to the correct Presto IP address. 
  • Confirm Client Set-up. 
  • Query Presto via a client browser on the subnet where you are not seeing printers:  
    • Example - If Presto is at IP, enter into a browser
    • This should return pong  If it does not, you likely have port TCP 9631 blocked from the client.  See Network Requirements

    Note:  On some networks, your server provides DHCP for an IP pool and the router provides DHCP for another IP pool.  If the IP is provided by the router, printers may not be visible.  Please contact  Collobos Support to resolve.

Printers can be seen, but print jobs are not visible in Presto.
  • You may have exceeded your licensed user limit.  Users will be prevented from printing and also be forced to authenticate if exceeding user limits.  Check your Presto Dashboard for Remaining Users.
  • Query Presto via a browser on the subnet where you are not seeing printers:
    • Example- if Presto is at IP, enter into a browser:
    • the result should return pong
    • If it does not, you likely have port TCP 9631 blocked from the client. See Network Requirements

Printers can be seen and print jobs are visible in Presto, but the print job doesn't print.
  • If you have Print Management, it's possible that's where the problem is as it sits in front of the queue.
  • If you are printing to other printers successfully, this is likely a print driver issue since Presto is working elsewhere.  Please install an alternate print driver (PCL's are generally preferred.)
Duplicate printers are displayed.

There are several reasons this could be happening:

  • AirPrint is enabled on the printer - An AirPrint printer has the ability to advertise itself on the local link generating advertising from both the printer and Presto.  Turning off AirPrint in the printer's settings will delegate the capability to Presto.
  • Duplicate printers appearing on an iOS device - Presto can generate both uDNS and mDNS advertisement of a printer.  mDNS can be disabled on the instance of Presto where the printer is installed.  For more details, see Hosts in Presto Administration.
Print Job appears wrong when printed.
  • Font/Sizing is wrong - The software looks to the default settings that you have set in your printer control panel.  If you make changes and they don’t match with your printout, try alternate print drivers. 
    • Windows users - PCL drivers are usually preferred over PS drivers. If this doesn't resolve the problem, then your printer may not be perfectly compatible. Often times you can find drivers on your printer manufacturer's support page and these may work better than those provided by Windows.

Troubleshooting Hosts

If a host is appearing as offline in the Presto Administrator, follow these steps to troubleshoot the problem:

  1. Confirm the system you're on is online.
  2. On the host system, launch Presto to confirm that it is offline.  See Accessing Presto in Presto Administration.
  3. Restart the Presto Service.  See Starting and Stopping the Presto Service, above.
  4. Relaunch Presto to confirm that you are back online.

If the above steps don't resolve the problem, re-run the installation executable on the Host system

Troubleshooting Firewall/Antivirus Software


Please allow following URL's through the Smoothwall web filter. 



Within SOPHOS cloud, please add the data paths to the global exclusions list.



Please allow following URL's through the Fortinet filter. 



Allow browsing by IP.

Uninstalling Presto


After running the uninstaller, delete the following folders for a complete uninstall:

  • C:\Program Files\Collobos
  • C:\ProgramData\Collobos
  • C:\Users\<userdirectory>\AppData\Roaming\Presto

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