Google Cloud Messaging
03 Apr 2016
Notifications vs data messages
| Feature |
Notifications |
Data Messages |
| Size |
<=2KB |
<=4KB |
| Collapsible |
Forced |
default no |
| Notification tray |
True |
False |
Messaging options
- High priorty message will wake a sleeping device when possible
- set time_to_live = 0 means messages that can’t be delivered immediately will be discarded
Topics
- 2KB limit
- Path must mathces regex
/topics/[a-zA-Z0-9-_.~%]+
- “to” field will set to topic path instead of registration token
- registration token is not needed
Device Groups
- Typically, “group” refers a set of different devices that belong to a single user
- 2KB for iOS, 4KB for other platforms
- registration token is needed
- Group registration tokens by notification_key
- Maximum number of member for each notication_key is 20
GCM Client
GCM XMPP server
- XMPP connection server reference
- XMPP app server sample
- production: gcm-xmpp.googleapis.com:5235
- testing: gcm-preprod.googleapis.com:5236
- 1000 connections in parallel for each sender ID
- CCS may send
CONNECTION_DRAINING message to indicate that the connection is being drained and will be closed soon
delivery_receipt_requested is for Downstream only?- Flow control
- Every message sent to CCS receives either an ACK or a NACK response.
- Messages that haven’t received one of these responses are considered pending.
- If the pending message count reaches 100, the app server should stop sending new messages and wait for CCS to acknowledge
HTTP vs XMPP
| Feature |
HTTP |
XMPP |
| Direction |
Downstream only |
Both |
| Call |
Synchronous |
Asynchronous |
| Json |
HTTP Post |
encapsulated in XMPP |
| Multicast downstream |
Supported |
Not supported |