This is only available on the latest releases
http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/rel_notes/11_5_1/cucm_b_release-notes-cucm-imp-1151/cucm_b_release-notes-cucm-imp-1151_chapter_010.html#concept_382237608FBFC8AA5231E0B32AF0A95D
On any previous release, you would only get the first message on all device, to find out which is the active one, and then just send messages to it.
HTH
java
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