What does "missing topic" error mean in APNS?

This seems to be covered in the Apple Guide on the subject:

The topic is currently the bundle identifier of the target application on an iOS device.

it solve，

now need to config topic, see request, for example: APNS MissingTopic is because you use first request, you should use second request, add a topic. it's OK

topic is your app's bundleID

1. single topic's request:

   HEADERS
   - END_STREAM
   + END_HEADERS
     :method = POST
     :scheme = https
     :path = /3/device/00fc13adff785122b4ad28809a3420982341241421348097878e577c991de8f0
     host = api.development.push.apple.com  
     apns-id = eabeae54-14a8-11e5-b60b-1697f925ec7b
     apns-expiration = 0
     apns-priority = 10
   DATA
   + END_STREAM
     { "aps" : { "alert" : "Hello" } }
   

2. multiple topic's request

   HEADERS
   - END_STREAM
   + END_HEADERS
     :method = POST
     :scheme = https
     :path = /3/device/00fc13adff785122b4ad28809a3420982341241421348097878e577c991de8f0
     host = api.development.push.apple.com
     apns-id = eabeae54-14a8-11e5-b60b-1697f925ec7b
     apns-expiration = 0
     apns-priority = 10
     apns-topic = <MyAppTopic> 
   DATA
   + END_STREAM
     { "aps" : { "alert" : "Hello" } }