Thanks for the suggestion. It makes sense to have such feature in the OpenIGTLink IF module.
Since there are some applications which do not want to push all the messages upon connection, I would add a flag (as an attribute) for outgoing MRML nodes. I pushed a test implementation to:

https://github.com/tokjun/OpenIGTLinkIF/tree/3501-send-all-outputs-on-connection

With this implementation, you can activate the suggested feature by setting "OpenIGTLinkIF.pushOnConnection" attribute to "1" in each MRML node. To test this:

1. Start the ReceiveServer sample program of OpenIGTLink (run "ReceiveServer 18944")

2. Create a connector node from OpenIGTLink IF module as a client ("localhost"/18944)

3. Create a new transform node. Suppose the node ID is "vtkMRMLTransformNode4"

4. Add the transform node under "OUT" branch in the I/O configuration interface in the OpenIGTLink IF module.

5. Open Python Interactor in Slicer and run:

   tnode1 = slicer.mrmlScene.GetNodeByID('vtkMRMLLinearTransformNode4')
   tnode1.SetAttribute('OpenIGTLinkIF.pushOnConnection', '1')

6. Activate the connector from OpenIGTLinkIF. The ReceiveServer will output a message that it received a transform from Slicer.

Please let me know what you think. If this works, the next step would be implementation of a GUI to control this attribute.

Thanks a lot for developing this so quickly! I test it and let you know how it works.

Thank you, I've tested it on Win7-64 and it works flawlessly!

Just one thing to consider: when a connection is established, there is no need to push the output nodes to all connections, only to the new connection that has been just established. If it's complicated to send selectively then it's OK to keep the current behavior.

GUI: Probably the simplest would be to add one more column to the I/O configuration table.

Some info that may be useful: I'm not sure if you know about this feature, the Data module has a MRML node inspector that can be used for adding/modifying custom node attributes, so there is no need for finding out the node ID, and entering python commands.

An unrelated enhancement request: when I create a new OpenIGTLink connection I have to click: +, the new connection name, Client radio button, and Active (4 clicks, quite far from each other, in different directions). It would be much more convenient (I could add an active connection by clicking on just two buttons, quite close to each other) if the new connection would be selected automatically and by default the 'Client' type would be selected by default.

Thanks again for the quick and good work!

There is no need to push the output nodes to all connections, only to the new connection that has been just established. If it's complicated to send selectively then it's OK to keep the current behavior.

Thanks for the feedback. This behavior is actually from vtkMRMLIGTLConnectorNode::PushNode() function. I implemented the requested feature by calling PushNode(), but this function only invokes an event that triggers data transfer , which could affect all connector nodes in the scene. I think this function should only push data to the specific connector.

GUI: Probably the simplest would be to add one more column to the I/O configuration table.

I was thinking about the same solution. I will work on this.

Great, thanks!

I addressed those two issues in tokjun/OpenIGTLinkIF 499186193e6be9a6f39ef5836213f4f8d4b8703f :

• vtkMRMLIGTLConnectorNode::PushNode() now pushes only nodes under the connector node.
• "Push on Connect" checkbox is added to I/O configuration

Please also note that "OpenIGTLinkIF.pushOnConnection" attribute is now renamed to "OpenIGTLinkIF.pushOnConnect" and only allows "true" / "false" values instead of "1"/ "0".

Thank you, I've tested it and works very well. There is only one strange thing: the "Push on connect" checkbox is displayed for the IN nodes as well. Does the checkbox have an effect for the IN nodes? If not, then probably it's better to hide or disable the checkbox for the IN nodes.

I agree. I removed the check boxes for the IN nodes.

The code has been merged to the main repository of OpenIGTLinkIF:

https://github.com/openigtlink/OpenIGTLinkIF/pull/18

Tested with latest nightly on Windows and it works well

For reference, this was fixed with r22727

Closing resolved issues that have not been updated in more than 3 months