Communication Protocol Used Between Client and Server

Data Format

For general requests and responses:

• Client based on the pure TCP protocol: varint-encoded payload length + payload (Protobuf-encoded TurmsNotification or TurmsRequest).
• Client based on the WebSocket protocol: payload (Protobuf-encoded TurmsNotification or TurmsRequest). The byte length of the payload is transmitted through the underlying WebSocket frame.

For heartbeat requests:

• Client based on the pure TCP protocol: a byte array [0] with the length of one byte. The value 0 here actually means "the length of the payload is 0 with a length of one byte under varint encoding", that is, the payload is 0 bytes.
• Client based on the WebSocket protocol: a binary message with an empty body (0 bytes).

Note: The reasons why Turms does not implement heartbeat through WebSocket's PING/PONG are:

• The time interval for sending PING frames implemented by each browser's WebSocket is different.
• The upper layer code cannot control the behavior of PING/PONG, or even perceive the occurrence of the behavior.
• The heartbeat logic at the network level should not be coupled with the heartbeat at the application layer.