evasmolders edited this page Nov 26, 2016 · 2 revisions

The HTTP protocol can be used to execute HTTP get commands to either retrieve information from an URL or if you have a device that can be controlled via HTTP you can use this protocol to talk to your device.

##OpenRemote Online Designer

Let's create a command which calls the Weather Underground API and extracts the temperature of a given location. We will use the command with a sensor to print the temperature on our user interface. If you want to use this weather service you can sign up for a limited free account here.

###Create new Device In "Building Modeler", create new device (New>New Device)


###Create commands Still in "Building Modeler", select the device that was created in step 1 and click on New>New Command Specify a name and select "HTTP" as protocol.


Protocol specific settings:

  • URL - The URL which will be called
  • HTTP Method - Specifies the HTTP request method GET is the safest and mostly used form, but specific applications may define their own preferred method.
  • Content-Type - Specifies type of media. Can be left blank, unless explicitly specified for a specific application as e.g. the XBMC application.
  • Workload - Can be String (eg. JSON data) which is send with the POST and PUT methods (Example also on XBMC page).
  • Username - If the URL is password protected, you can provide a username.
  • Password - Here comes the password of that user.
  • XPath expression - If the returned page is a XML document, you can use Xpath to extract information from that XML. See our short introduction to Xpath usage.
  • Regular expression - If the result is not XML, you might be able to use a regular expression to extract the information you need.
  • Polling interval - If you link this command to a sensor, the polling interval is used to update the sensor periodically.
  • JSONPath Expression - which can be used to extract data from a JSON response, examples can be found here. Stefan Goessner's mini tutorial on JSONPath.

The Wunderground Weather API URL looks like this: Replace YOURKEY with the number you received from Wunderground. The Xpath expression for temperature in C is //response/current_observation/temp_c Use polling of 10 minutes to not exceed the limits of free usage of Wunderground

Since we are not going to add any other command, click on "Submit".

###Create sensors

The command will return a value and we want that value to be printed in out UI. For this we need a sensor that is linked to our command. I will use a custom sensor wich will just return the result as a string.


Done! Now we have the device, the command and the sensor.


###Use commands in UI Designer

Now we switch to the UI Designer and create our user interface. The panel will contain 2 labels. One has a static text and the other one is linked to our sensor.



It's currently 5 degrees in Bielefeld :)


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