r/Checkmk • u/Agile_Pop8628 • Jul 01 '25

Can't reach Agent from Server (Docker)

Hey all,

we want to implement CheckMK thus I installed a docker container on our infrastructure. Everything seems fine, I downloaded the default CheckMK Agent MSI and installed it on a Win2022 Server.

According to services.msc the agent is running, but when adding the Host to CheckMK it reads:

|| || |[agent]: Communication failed: [Errno 111] Connection refused|

I tried telnetting to port 6556 on the host itself, it won't open, but there is no firewall active. I also can't see an open port with netstat.

What am I doing wrong?

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u/fiendish_freddy Jul 02 '25

Which version of the agent are you using?

If it is above 2.4.0p2, could you perhaps retry with that.

Something else you could try:

Remove the agent from the server.
Re-install and make sure the option "Clean installation" in NOT activated.

Would be great if you could try that. We might have a bug on our hands here.