Hi mbenson,

Please can you confirm that there was a typo and you mean the getItemData method?
In any case, in order to implement a one-to-one comunication you should use the notifyUserMessage to receive the request sent by the client through the sendmessage.
Then you should create a personal Item, for example customizing it in the getItems method, on which the client is subscribed and push the reply on it.

For an example of one-to-one comunication please refer to this demo (technology used is JavaScript for the client side and Java for the server side).

Please, let us know if you need further clarification.