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Why does my HTTP XML/REST Value sensor return a 404 error?



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I set up an HTTP XML/REST Value sensor to monitor a REST/JSON value. When the sensor runs, it returns the following error: Protocol Error: The remote server returned an error. (404) Not Found. The error code is code: PE023.

I tested the URL from the probe system in a browser and it works fine. It requires authentication, but I have set up that as well. The URL has the following format: This works fine from the system that the probe is running on, but it does not work through PRTG. Is there something in the URL that causes this issue?

404 dotnet error-messages http-sensor http-xml pe023 prtg special-characters url

Created on Jan 22, 2013 4:04:53 PM by  Gerald Schoch [Paessler Support]

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This article applies to PRTG Network Monitor 12 or later

Fixing HTTP XML/REST Value Sensor’s 404 Error

The HTTP XML/REST Value Sensor returns an error when the URL contains specific URL encoded characters. In the case of the question above, the character sequence %2F is the reason for this issue. Sometimes the XML/REST sensor (based on .NET) encodes such a sequence again—resulting in a broken URL.


The solution for this issue is to create a new configuration file. This file will force PRTG’s .NET XmlValue.exe file to interpret special characters correctly. In this case this means not to escape this character again but to keep the URL encoded.

PRTG runs the XmlValue.exe file with every scan. If there is a corresponding configuration file available, the instructions in this file will be considered while running XmlValue.exe. Thus, we can use a configuration file to fix this problem.

Steps to Go

  1. Open a new text editor.
  2. Copy the following text into the editor: <?xml version="1.0"?> <configuration> <startup> <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/> </startup> <uri> <schemeSettings> <clear/> <add name="http" genericUriParserOptions="DontUnescapePathDotsAndSlashes"/> </schemeSettings> </uri> </configuration>
  3. Save the text file under the file name XmlValue.exe.config
  4. Save this file to the sub folder Sensor System of the PRTG program directory. Now PRTG is able to grab the correct value.

See Also

PRTG Manual: HTTP XML/REST Value Sensor

Created on Jan 22, 2013 4:11:23 PM by  Gerald Schoch [Paessler Support]

Last change on Jan 22, 2013 4:13:04 PM by  Gerald Schoch [Paessler Support]

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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.