Hello,

after upgrading to 18.4.47.1962, our PRTG-Installation fails to startup. Service "PRTG Core Server Service" tries to start - but not finishes startup. In serverlog, we can see, that all ports on the second IP of this NIC are occupied.

CheckPortIsFree: Port 8443 on <2nd ip> is occupied.. Waiting, retrying.. 
CheckPortIsFree: Port 8444 on <2nd ip> is occupied.. Waiting, retrying.. 
...
CheckPortIsFree: Port 8584 on <2nd ip> is occupied.. Waiting, retrying..

Then I tried to install from this https://helpdesk.paessler.com/en/support/solutions/articles/83364-update-from-18-1-36-not-possible but it did not solved my problem. Log filled up with same checkportisfree message.

Then I deleted the 2nd ip from my nic and restartet services - and it worked.

Article Comments

Hi there,

It seems that something blocks PRTG from opening any webports - any. Could you check if there is some kind of AntiVirus (or anything similar) installed? If so, please temporary stop these services and restart PRTG. Afterwards open the "PRTG Administration Tool" and check if the settings within the "Web Server"-tab are still correct.

Best regards.


Jan, 2019 - Permalink

Nope, this is a dedicated machine. there is no other software installed, than prtg. And the error is reproducible. When I add a second IP to my NIC, restart the machine, the error comes up. When I delete the second IP and restart the machine. The error is gone. After restarting I can readd the 2nd IP.


Mar, 2019 - Permalink

Hi there,

After adding the second NIC, please open the "PRTG Administration Tool" and check if the settings within the "Web Server"-tab are still correct and what IPs are selected there.

Best regards.


Mar, 2019 - Permalink