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PRTG Manual: HTTP Content Sensor

The HTTP Content sensor monitors numeric values returned by an HTTP request.

In the returned HTML page, each value must be placed between brackets [ ]. See section Example.

This sensor implicitly supports SNI, an extension to the Transport Layer Security (TLS) protocol.

HTTP Content Sensor

For a detailed list and descriptions of the channels that this sensor can show, see section Channel List.

Sensor in Other Languages

Dutch: HTTP (Inhoud)
French: Contenu (HTTP)
German: HTTP (Inhalt)
Japanese: HTTP コンテンツ
Portuguese: Conteúdo HTTP
Russian: HTTP: Содержимое
Simplified Chinese: HTTP 内容
Spanish: Contenido HTTP

Remarks

Consider the following remarks and requirements for this sensor:

Remark	Description
Channels	This sensor does not officially support more than 50 channels.
SRP ciphers	This sensor does not support Secure Remote Password (SRP) ciphers.
Smart URL replacement	This sensor supports smart URL replacement.
IPv6	This sensor supports IPv6.
Performance impact	This sensor has a medium performance impact.
Knowledge Base	Knowledge Base: How can I monitor internal values of a web application with PRTG? Knowledge Base: Which HTTP status code leads to which HTTP sensor status?

Add Sensor

Setting	Description
Number of Channels	Define how many values the .html file returns. The sensor handles each value in its own channel. Each value must be placed between brackets [ ]. Enter the number of bracket-value pairs that the URL returns. Enter an integer. Do not enter a number that is greater than the number of values that the HTTP request returns. Otherwise, you get an error message.

Setting

Description

Number of Channels

Define how many values the .html file returns. The sensor handles each value in its own channel. Each value must be placed between brackets [ ]. Enter the number of bracket-value pairs that the URL returns. Enter an integer.

Do not enter a number that is greater than the number of values that the HTTP request returns. Otherwise, you get an error message.

Basic Sensor Settings

The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:

httpsensor

For more information about basic sensor settings, see section Sensor Settings.

HTTP Specific

Setting	Description
Timeout (Sec.)	Enter a timeout in seconds for the request. Enter an integer. The maximum timeout value is 900 seconds (15 minutes). If the reply takes longer than this value, the sensor cancels the request and shows a corresponding error message.
Script URL	Enter the URL that the sensor connects to. If you enter an absolute URL, the sensor uses this address independently of the IP Address/DNS Name setting of the parent device. The URL must be URL encoded. PRTG uses a smart URL replacement with which you can use the parent device's IP address or Domain Name System (DNS) name setting as part of the URL. For more information, see section Smart URL Replacement.
Value Type	Define what kind of values the .html file returns: Integer: Returns integers. Float: Returns floats with a dot . between the predecimal position and the decimal places. The sensor also displays integers unless they do not produce a buffer overflow. The sensor cannot handle string values. You cannot change this value after sensor creation.

Setting

Description

Timeout (Sec.)

Enter a timeout in seconds for the request. Enter an integer. The maximum timeout value is 900 seconds (15 minutes).

If the reply takes longer than this value, the sensor cancels the request and shows a corresponding error message.

Script URL

Enter the URL that the sensor connects to. If you enter an absolute URL, the sensor uses this address independently of the IP Address/DNS Name setting of the parent device.

The URL must be URL encoded.

PRTG uses a smart URL replacement with which you can use the parent device's IP address or Domain Name System (DNS) name setting as part of the URL. For more information, see section Smart URL Replacement.

Value Type

Define what kind of values the .html file returns:

Integer: Returns integers.
Float: Returns floats with a dot . between the predecimal position and the decimal places. The sensor also displays integers unless they do not produce a buffer overflow.

The sensor cannot handle string values.

You cannot change this value after sensor creation.

Advanced Sensor Data

Setting	Description
If Content Changes	Define what the sensor does if the content of the web page changes: Ignore (default): Do nothing. Trigger 'change' notification: Send an internal message that indicates a change. In combination with a change trigger, you can use this to trigger a notification if a change occurs.
Result Handling	Define what PRTG does with the sensor result: Discard result (default): Do not store the sensor result. Store result: Store the sensor result and the last response in the \Logs\sensors subfolder of the PRTG data directory on the probe system. The file names are Result of Sensor [ID].txt and Result of Sensor [ID].Data.txt. This setting is for debugging purposes. PRTG overwrites these files with each scanning interval. This option is not available when the sensor runs on the hosted probe of a PRTG Hosted Monitor instance. In a cluster, PRTG stores the result in the PRTG data directory of the master node.

Setting

Description

If Content Changes

Define what the sensor does if the content of the web page changes:

Ignore (default): Do nothing.
Trigger 'change' notification: Send an internal message that indicates a change.
In combination with a change trigger, you can use this to trigger a notification if a change occurs.

Result Handling

Define what PRTG does with the sensor result:

Discard result (default): Do not store the sensor result.
Store result: Store the sensor result and the last response in the \Logs\sensors subfolder of the PRTG data directory on the probe system. The file names are Result of Sensor [ID].txt and Result of Sensor [ID].Data.txt. This setting is for debugging purposes. PRTG overwrites these files with each scanning interval.

This option is not available when the sensor runs on the hosted probe of a PRTG Hosted Monitor instance.

In a cluster, PRTG stores the result in the PRTG data directory of the master node.

Authentication

Setting	Description
Authentication	Define if authentication is necessary on the web page: Web page does not need authentication (default) Web page needs authentication
User Name	This setting is only visible if you select Web page needs authentication above. If the proxy requires authentication, enter the user name for the proxy login. Enter a string.
Password	This setting is only visible if you select Web page needs authentication above. Enter a password.
Authentication Method	This setting is only visible if you select Web page needs authentication above. Select the authentication method that the URL uses: HTTP authentication (default): Use simple HTTP authentication. This authentication method transmits credentials as plain text. NT LAN Manager authentication: Use the Microsoft NT LAN Manager (NTLM) protocol for authentication. Digest access authentication: Use digest access authentication. This applies a hash function to the password, which is safer than HTTP authentication (default).

Sensor Display

Setting	Description
Primary Channel	Select a channel from the list to define it as the primary channel. In the device tree, PRTG displays the last value of the primary channel below the sensor's name. The available options depend on what channels are available for this sensor. You can set a different primary channel later by clicking below a channel gauge on the sensor's Overview tab.
Graph Type	Define how this sensor shows different channels: Show channels independently (default): Show a graph for each channel. Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This generates a graph that visualizes the different components of your total traffic. You cannot use this option in combination with manual Vertical Axis Scaling (available in the channel settings).
Stack Unit	This setting is only visible if you select Stack channels on top of each other above. Select a unit from the list. PRTG stacks all channels with this unit on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.

Setting

Description

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, PRTG displays the last value of the primary channel below the sensor's name. The available options depend on what channels are available for this sensor.

You can set a different primary channel later by clicking below a channel gauge on the sensor's Overview tab.

Graph Type

Define how this sensor shows different channels:

Show channels independently (default): Show a graph for each channel.
Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This generates a graph that visualizes the different components of your total traffic.
You cannot use this option in combination with manual Vertical Axis Scaling (available in the channel settings).

Stack Unit

This setting is only visible if you select Stack channels on top of each other above.

Select a unit from the list. PRTG stacks all channels with this unit on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.

Inherited Settings

By default, all of these settings are inherited from objects that are higher in the hierarchy. We recommend that you change them centrally in the root group settings if necessary. To change a setting for this object only, click under the corresponding setting name to disable the inheritance and to display its options.

For more information, see section Inheritance of Settings.

Example

For example, consider the URL http://www.example.com/status.html that returns a PHP script with the current system status in a simple HTML page as follows:

<html>
<body>
Description: Script gives back current status of disk free (%) and CPU usage (%).
[85.5][12.0]
</body>
</html>

You would configure the HTTP Content sensor using

the Script URL from above,
the value type Float,
and the number of channels 2.

The sensor calls the URL with every scanning interval and only regards the two values in brackets [ ] and handles each of them in one channel. The additional description text and HTML tags are not necessary. In this example, they are added in case a human calls the URL.

If you define the number of channels as 1, the sensor only reads the first value. The second value is ignored. Using 3 as the number of channels results in a sensor error message.

Smart URL Replacement

Instead of entering a complete address in the URL field of an HTTP sensor, you can only enter the protocol followed by a colon and three forward slashes (this means that you can enter either http:/// or https:///, or even a simple forward slash / as the equivalent for http:///). PRTG automatically fills in the parent device's IP Address/DNS Name in front of the third forward slash.

Whether this results in a valid URL or not depends on the IP address or Domain Name System (DNS) name of the parent device. In combination with cloning devices, you can use smart URL replacement to create many similar devices.

For example, if you create a device with the DNS name www.example.com and you add an HTTP sensor to it, you can provide values in the following ways:

If you enter https:/// in the URL field, PRTG automatically creates the URL https://www.example.com/
If you enter /help in the URL field, PRTG automatically creates and monitor the URL http://www.example.com/help
It is also possible to provide a port number in the URL field. It is taken over by the device's DNS name and is internally added, for example, http://:8080/

Smart URL replacement does not work for sensors that run on the probe device.

Channel List

Which channels the sensor actually shows might depend on the target device, the available components, and the sensor setup.

Channel	Description
Downtime	In the channel table on the Overview tab, this channel never shows any values. PRTG uses this channel in graphs and reports to show the amount of time in which the sensor was in the Down status.
[Value]	The numeric values that an HTTP request returns in several channels