RESTful and XML Integration

Hello,
I own an eta pellet unit and was able to use this instructions to setup rest sensors for temperature, pressure and even the status and the amount of pellets. Now I wanted to setup the switches of the pellet unit too. I’ve to make POST requests application/x-www-form-urlencoded and submit ‘value’: 1803 for on
and ‘value’: 1802 for off.
For the status of the switch I got the following XML answer to my GET request:

<eta xmlns="http://www.eta.co.at/rest/v1" version="1.0">
<value uri="/user/var/120/10101/0/0/12080" strValue="Aus" unit="" decPlaces="0" scaleFactor="1" advTextOffset="1802">1802</value>
</eta>

or

<eta xmlns="http://www.eta.co.at/rest/v1" version="1.0">
<value uri="/user/var/120/10101/0/0/12080" strValue="Ein" unit="" decPlaces="0" scaleFactor="1" advTextOffset="1802">1803</value>
</eta>

in node red I used a function node for the body of the post request, it works, but I want to transfer it to the rest or the command line switch.

Function Node:

msg.headers={ 
    'Content-Type': 'application/x-www-form-urlencoded'
};
msg.payload = {};
msg.payload={ 
    'value': 1803
};
return msg;

I tried the following switches:

Rest switch:

  - platform: rest
    resource: http://192.168.1.128:8080/user/var/40/10021/0/0/12080
    name: Heizkessel Switch ETA
    method: post
    body_on: '{"value": 1803}'
    body_off: '{"value": 1802}'
    is_on_template: '{{ value_json == body_on }}'
    headers:
      Content-Type: application/x-www-form-urlencoded

or

  - platform: command_line
    switches:
      test_heizkessel:
        command_on: 'curl -X POST -H ‘Content-Type: application/x-www-form-urlencoded’ -d ‘{“value”:"1803"}’ http://192.168.1.128:8080/user/var/40/10021/0/0/12080”'
        command_off: 'curl -X POST -H ‘Content-Type: application/x-www-form-urlencoded’ -d ‘{“value”:"1802"}’ http://192.168.1.128:8080/user/var/40/10021/0/0/12080”'
        command_state: "/usr/bin/curl -X GET http://192.168.1.128:8080/user/var/40/10021/0/0/12080"

both without success. Can anybody help me with this?

Thanks Daniel