Android：开发聊天应用

Question

I am developing an one-to-one chat app. The problem is how should I keep all clients and server in sync? There can be multiple cases when the message fails to send from the client, or it is not received by the client.

Right now, I am using a pub sub service and GCM. Whenever user is using the app, I subscribe to a unique channel to receive messages and use api to send message. Also, through pubsub I am maintaining user online status.

Whenever app goes into background, pubsub disconnects and user goes offline. In this case GCM is used to deliver messages to the client.

This systems is working fine. But rarely there are messages that are not delivered to the client.

Can this be improved to assure message delivery ?

Answer 1

Here is a good tutorial. with client side and server side codes...