Chapter 17

Websocket

Websocket enables bidirectional, message-oriented streaming of text and binary data between client and server. It is the closest thing to a raw network socket in the browser that we have.

The WebSocket resource URL uses its own custom scheme: ws for plain-text communication and wss for encrypted (TLS) communication. Why the custom scheme, instead of http/s? The primary use case for the Websocket protocol is to provide an optimized, bidirectional communication channel between applications running in the browser and server. However, the WebSocket wire protocol can be used outside of the browser and could be negotiated via a non-http exchange.

WebSocket communication consists of messages and application code and does not need to worry about buffering, parsing and reconstructing received data. For example, if the server sends a 1 MB payload, the applications onmessage callback will only be called once the client receives the entire payload.

WebSockets can transfer test or binary data.