Using a Heartbeat to Detect Disconnection

The AMPS client includes a heartbeat feature to help applications detect disconnection from the server within a predictable amount of time. Without using a heartbeat, an application must rely on the operating system to notify the application when a disconnect occurs. For applications that are simply receiving messages, it can be impossible to tell whether a socket is disconnected or whether there are simply no incoming messages for the client.

When you set a heartbeat, the AMPS client sends a heartbeat message to the AMPS server at a regular interval, and waits a specified amount of time for the response. If the operating system reports an error on send, or if there is no activity received from the server within the specified amount of time, the AMPS client considers the server to be disconnected. Likewise, the server will ensure that traffic is sent to the client at the specified interval, using heartbeat messages when no other traffic is being sent to the client. If, after sending a heartbeat message, no traffic from the client arrives within a period twice the specified interval, the server will consider the client to be disconnected or nonresponsive.

The AMPS client processes heartbeat messages on the client receive thread, which is the thread used for asynchronous message processing. If your application uses asynchronous message processing and occupies the thread for longer than the heartbeat interval, the client may fail to respond to heartbeat messages in a timely manner and may be disconnected by the server.