This article applies to PRTG Network Monitor 19 or later
PRTG automatically determines which ports to use
You have set the PRTG web server to use SSL on port 443. However, on startup the PRTG server checks if port 80 is used on the host computer. If it is not, PRTG sets a redirect for port 80: All web connections to this port are redirected to port 443.
This is to avoid users seeing a "Connection failed" message in case they do not include https:// when calling the PRTG web interface.
If you want to use port 80 for other web applications, this is an undesired behavior, of course. There are two solutions for this.
Solution #1: start other services earlier than PRTG
If you start a program or service that uses port 80 prior to PRTG, port 80 will already be taken on PRTG startup and therefore not be blocked.
This can be achieved, for example, by changing settings in the Windows services. There, you can start the PRTG service dependent on for example an Apache service, so that the Apache web server starts first.
Solution #2: registry hack
If solution #1 is not possible in your case, you can add a registry entry that disables port 80 redirection for PRTG.
Important: Please make proper backups before editing the registry!
In the registry editor, go to
32-bit: HKLM\Software\Paessler\PRTG Network Monitor\Server\Webserver
64-bit: HKLM\Software\Wow6432Node\Paessler\PRTG Network Monitor\Server\Webserver
Note: For the deprecated PRTG versions 7 and 8, you might see the values in the additional sub-key V7 or V8.
There, create a new DWORD value with the name
NoSSLRedirect
Set this value to 1 to disable port 80 redirection. Set it to 0 to enable port 80 redirection again.
More
Add comment