websockets An interview trend I’ve come across in is being asked about WebSockets. WebSockets is a technology that allows clients/browsers to communicate with servers and vice versa persistently. This differentiates from the traditional paradigm of clients sending requests and servers fulfilling those requests.
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As with other connections, a handshake is initiated by the client with a constructor utilizing ws:// or wss:// protocol. Once the handshake is complete, data (the payload) is sent without latency costs like traditional HTTP requests. This is because a single HTTP connection is needed and reused for a WebSocket connection. Supported by the browser, pings and pongs are also sent between the server and client to check if the connection is still open.
An immediate, bi-directional connection is best for the following applications:
- interactive games
- collaborative source code editors
- online chat rooms
- real-time apps with a lot of data and many users
Once the connection is established, the WebSockets API executes these four different events:
- open - occurs when connection exist
- message - occurs when data is received
- error - self-explanatory
- close - occurs when the connection is closed
and the following methods:
- send - used to send data
- close - used to close the connection
If you’re more curious over other interactions between clients and servers, read this StackOverflow answer to get started.
Check out Socket.io, a popular WebSocket library.