UPnP-2-xPL gateway

In an attempt to get more control over the UPnP devices from Girder, my homeautomation server, I created a gateway from UPnP to xPL. Using the xPLGirder component it allowed me to connect to the UPnP devices from Girder.

The gateway supports discovery, update events and methods calls. Currently the only client available is a Girder client (and xPL message handler within xPLGirder), though other clients can be created using the included message schemas.

A UPnP device will be dissected into its components and each component will get its own unique ID. The components are;

  • Device
  • Subdevice
  • Service
  • Variable
  • Method
  • Argument

The ID tag for the elements are a comma-separated list, of which the first one is the ID of that element, the others are sub elements (child elements).

Uniqueness

The component IDs will NOT remain the same over sessions, they will be regenerated for each new session. So you should not rely on them. You should rely only on the UDN (unique device name, usually a UUID) of the UPnP device.

Announcing a new UPnP device

When a new device is added, it is dissected into its components. For each component a separate announce message will be send. Its a trigger message defined as follows;

 upnp.announce {
 announce = 
 id = 
 [parent = ]
 [element specific data]
 }

Remarks;

  • only a ‘device’ and ‘left’ anounce message will NOT have a ‘parent’ key
  • The  is a list starting with the elements own ID and followed by any children it has (only 1st level children, not recursive)
  • an ‘announce=left’ message is used to indicate a device leaving, it will only have the ‘id=…’ key value pair. Indicating who has left. There will always be only 1 root device leaving per message, and hence the id will only contain the id of the root device leaving (no child IDs).
  • the ‘allowed’ key will contain the allowvaluelist in a comma separated format

Devices leaving

A special case of the announce message will be send. See ‘Announcing a new UPnP
device’.

Announce requests

To request a device to announce again, send a command message;

 upnp.basic
 {
 command = announce
 [id = ]
 [id = ...]
 }
This will trigger a new announce cycle, which will announce all elements of the requested ID again. If no ID is provided, then all devices known by the getway will announce again. At start up an application may broadcast this command to discover all UPnP devices available. Multiple requests can be combined by having multiple ID keys, each with 1 ID requested.

Value updates (StateVariable events)

Whenever an evented state variable changes its value, the event will result in a trigger message;

 upnp.basic
 {
  = 
 [ = ]
 }

The keys of this message will correspond to the ID’s of the statevariable who’s value changed. The value, is the new value of the variable. Generally, its only a single value per message. Devices that use the ‘LastUpdate’ mechanism as described in the AV Rendering Control description (version 1.0, par 2.3) will get more than one value.

In case a value is too large, it will be chopped in pieces. Example; the ID = 34, then the following is returned as part of the message;

 34=<>
 34-1=this is part 1
 34-2=this is part 2
 34-3=etc.

So if the ID returns “<>”, then the receiver should look for the ID with sub-numbers, the values can be concatenated to get back to the original value.

The ‘LastUpdate’ type updates are for devices supporting multiple instances, the gateway will only handle the first, and will handle the elements within it as separate statevariable updates.

Call methods

To call a method on a device, use the following command message;

 upnp.method
 {
 command=methodcall
 method=
 [callid=]
 [=]
 [=]
 }

the key ‘callid’ is optional and is returned with the response so the command and its response can be connected back together (calls are async).

The response will be a trigger message;

 upnp.method
 {
 [callid=]
 success=
 [error=error text]
 [retval=]
 =
 [=]
 }

The callid value will be only be present if provided with the command, and will have the same value that was provided with the command. The key ‘success’ is a boolean indicating success. In case of failure the ‘error’ key indicates the error message, no other keys will be provided. In case of success, no ‘error’ key will be available, but the returnvalue (retval) will be present along with all id’s and values of arguments with direction ‘out’. The ID’s and the values represent the arguments and the returned values. In case a value is too large, it will be chopped in pieces, see the ‘value updates’ section above.

 

Download UPnP-2-xPL gateway (downloaded 31834 times).

For support, please use the xPL forums

Be Sociable, Share!

Leave a Reply

Your email address will not be published. Required fields are marked *

 

Subscribe without commenting