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Connection Limit Reached on Print Server or License Server

Problem​

If users are experiencing failed print jobs, printer queries that don't complete, or license check failures—especially during peak usage times—you might be hitting the connection limit on your Print Server or License Server. Both ScrewDrivers Print Server Agent v6 and Tricerat License Server v2 have a built-in connection limit of 256 concurrent connections by default. This limit's there to protect your server from becoming unstable if something goes wrong and connection counts spike unexpectedly.

When you reach this limit, the server starts refusing new connections, which means no more printing until some connections close. This typically happens in large environments with heavy print traffic or during times when many users are logging in simultaneously.

How to Identify This Issue​

If you've enabled logging for your License Server or Print Server, you'll see this telltale line in the log file when the limit's been reached:

FAIL: Connection limit of 256 reached on port 3550. Connection refused.

Solution​

If you're hitting the connection limit during normal production operations, you can safely increase it. This is a fairly common adjustment in large environments. Here's how to modify the limit:

  1. Open the Registry Editor by running regedit.exe

  2. Navigate to the appropriate registry key:

    • For License Server: HKEY_LOCAL_MACHINE\SOFTWARE\triCerat\Simplify Licensing
    • For Print Server: HKEY_LOCAL_MACHINE\SOFTWARE\Tricerat\Simplify Printing\ScrewDrivers Print Server v6

  3. Create a new REG_DWORD value named ConnectionLimit

  4. Set the value to your desired maximum concurrent connections:

    • Default: 256
    • Recommended for large environments: 512 or 1024
    • Setting it to 0 disables the limit entirely (allows unlimited connections)

  5. Restart the service for the change to take effect

Tricerat's Recommendation​

If 256 isn't enough for your environment, we recommend increasing the value to 512 or 1024 rather than disabling the limit entirely. While disabling the limit is generally safe, keeping some limit in place protects your server from runaway connection scenarios that could consume excessive system resources.

Understanding Connection Behavior​

It helps to understand when connections actually occur so you can estimate what limit makes sense for your environment. For a Print Server, connections happen at three key times:

During user logon: A brief connection queries the Print Server for information about the printers that need to be created for that user. This connection typically lasts just a few seconds.

During print jobs: A connection opens to send print data to the Print Server. Most print jobs complete within seconds, though large documents can take longer.

When opening Advanced Print Features: Users opening the Advanced Print Features dialog triggers a connection to retrieve printer capabilities.

All these connections are non-persistent—they close as soon as the operation completes. Since connections typically last only seconds, the connection limit really comes down to how many simultaneous operations occur in any given moment. In most environments, you'd only hit the 256 default limit during peak login times (like Monday morning) or if you've got hundreds of users printing simultaneously.

When to Adjust This Setting​

Generally, you should only change this setting if you're actually seeing the connection limit errors described in the Problem section, or if Tricerat Support recommends it for your specific environment. The default of 256 works fine for most deployments.

If you're regularly hitting the limit during normal operations, that's a clear signal your environment needs a higher value. But if you're not seeing those "connection limit reached" errors in your logs, there's no need to adjust it.