Questions:
What does it mean that web sockets are bidirectional? Why is this useful?
Web sockets allow a single TCP socket connection to be hijacked so that the client-server relationship can relay bi-directional, full-duplex messages instantaneously. This means that messages can be sent and received in real time and memory use is configurable.
Source: https://medium.com/@nerdplusdog/websocket-simultaneous-bi-directional-client-server-communication-e7948203054b
Does socket.io use HTTP? Why?
Yes - socket.io is a communication library that uses websockets where appropriate, however initial connection setup is done over HTTP. HTTP is also useful for some transports, and can serve as a fallback for websockets.
Source: https://stackoverflow.com/questions/37836130/socket-io-why-does-it-need-an-http-server#:~:text=The%20premise%20on%20which%20your,%2C%20which%20it%20isn’t.&text=Even%20when%20websockets%20can%20be,%2Fsocket.io.js%20.
What happens when a client emits an event?
Events emitted by the client are sent to the server to be handled.
What happens when a server emits an event?
Events emitted by the server can be sent to all connected clients or to a specified segment of clients by specifying a namespace or room. Clients who receive the event may have functions in place to handle the event.
What happens if a client “misses” an event?
Missed events are analogous to unhandled events - nothing ‘happens’.
How can we mitigate this?
- Confirm that event handlers are in place to perform necessary actions meant to be triggered by events.
- Include error handlers as a second layer of event handling if things don’t work as intended
Definitions
| Term | Definition | Source |
|---|---|---|
| Web Socket | Bidirectional, full-duplex protocol that is used in the same scenario of client-server communication but starts from ws:// or wss://. | https://www.geeksforgeeks.org/what-is-web-socket-and-how-it-is-different-from-the-http/ |
| Socket.io | JavaScript library for realtime web applications that enables realtime, bi-directional communication between web client and servers. Includes a client-side library that runs in the browser and a server-side library for Node.js | https://en.wikipedia.org/wiki/Socket.IO |
| Client | The receiving end of a service or the requestor of a service in a client/server model type of system. | https://www.techopedia.com/definition/437/client |
| Server | A computer that provides data to other computers. | https://techterms.com/definition/server#:~:text=A%20server%20is%20a%20computer,the%20purpose%20of%20the%20server. |