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PRTG switched the HTTP server to but not the sensor



I have two related problems with my local PRTG installation:

Problem 1. My local PRTG server has switched to serving out its status website from the address, after a few weeks of working well on the local host’s IP address at 10.0.0.x. The web settings were appropriate to be using the local machine's IP address, but still the server started on the localhost IP. It appears to be complaining that the ports it wants (80 or 8080) are already in use, even though I have no other HTTP server running on this host. Running "netstat -o" doesn't show any local connections open on the server's IP address 10.0.0.x port 80 or 8080, and yet PRTG gives up and starts on What the heck?

Problem 2. So, fine, whatever. I don’t mind using localhost, since I’m watching the PRTG status from a local browser window pointed to the localhost address. So I switched the web settings to always start it on However, I still see the sensor monitoring the 10.0.0.x IP address always has a failed status, obviously because the server moved to the localhost address. Shouldn’t the sensor have moved to when the server decided to start on the localhost address? I realize I should be able to tweak some settings in that sensor, to get it to monitor the localhost address instead, but I’m somewhat frustrated that I should have to do that. Especially if the server later decides to switch back to the 10.0.0.x address, at which point, I’ll have to manually force the sensor back.

Am I missing something? Is there a way to get this working in a more reliable, hands-off way?

P.S. I started trying to use PRTG to monitor a few devices on my home network, especially wanting to monitor the reliability of my Internet access over time. I was thrilled to see it watching local disk available space, and the Sonos devices on my network as well. I saw that when the trial period expired after a month, it would be limited to 100 probes, and that seemed quite reasonable, for my unexciting home network.

After a few weeks, I realized it had stopped monitoring, so I started it back up. I tried the home screen shortcut, but it didn't work, so I restarted the windows service, and that seemed to get it going. It took me a short time, to notice it had switched to the localhost address, probably during that restart. It's not a huge deal, since I'm only accessing it from the local computer, but I'm not comfortable running software that's complaining about problems, and I'd really like to get to the bottom of this.

failed http localhost prtg sensor server

Created on Nov 1, 2022 7:46:06 PM

1 Reply



Hello there,

Thanks for the KB post.

You mentioned that 'PRTG server has switched to serving out its status website from the address, after a few weeks of working well on the local host’s IP address at 10.0.0.x'.

Could you please share with me what is set in the PRTG Administrator Tools's PRTG Web Server tab?

Under the field of IP Address for PRTG Web Server, are you selecting the second option which is 'All IP addresses available on this computer (recommended)'?

Also, when this issue happens, do you aware of any changes on the PRTG Core Server such as restart or reboot? Is the Core Server up and running all the while without rebooting?

With kind regards,
Chan Siau Hen
Technical Support Team, Paessler AG

Created on Nov 5, 2022 10:58:52 AM by  Chan Siau Hen [Paessler Technical Support]

Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.