Werk #19193: Windows agent now opens firewall port before starting the agent controller
| Component | Checks & agents | ||||||
| Title | Windows agent now opens firewall port before starting the agent controller | ||||||
| Date | Mar 31, 2026 | ||||||
| Level | Trivial Change | ||||||
| Class | Bug Fix | ||||||
| Compatibility | Compatible - no manual interaction needed | ||||||
| Checkmk versions & editions |
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The Windows Checkmk agent opens a TCP port in the system firewall to allow incoming connections to the agent controller. Previously, the firewall port was opened after the controller process had already started. If the controller attempted to bind to the port before the firewall rule was in place, it would crash.
The startup sequence has been corrected: the firewall port is now opened before the controller starts, ensuring the port is available when the controller needs it.
No manual action is required. The fix is applied automatically after updating the Windows agent.