How to achieve a reliable IM instant messaging application

The current IM application many, can have the following several ideas:
If you have a server, you can use a number of clients to connect to the server, the server for message forwarding, using a long connection way. The XMPP protocol can be used, and the server can refer to the open source OpenFire.
If you do not have a server, you can use a third-party IM platform to connect to the platform via the client and let the platform forward the message. The advantage of this is that it is not necessary to develop and maintain the message push process, but the performance of communication is obviously affected by the third party.

With the ring-letter platform, we can develop an Android app and a Web client, Web client mounted on the Sina server, so that we can use CS and BS in the way of peer-to-peer communication, group chat and so on, including hair text, pictures, videos, calls and so on.

Ring-letter platform just retains the ID, password information, so we can build a server, the user's information on our own server, and the ID and password through the encryption map to the ring platform, so that users log on to our server, and then indirectly connected to the ring server, to achieve communication functions.

If we want to implement a chat room, you can do this, create a chat room, the user logged into the group chat.

How to achieve a reliable IM instant messaging application