服务器端事件+客户端事件vs Websocket

Question

I am updating an old system that used to use an ajax polling mechanism. The script would periodically call the back-end looking for updates, and rarely the user would make an ajax request to send data. I first wanted to use Web Sockets because I could instantly get the data from push events, and because the connection stays open. I then read about Server Side Events, and how it is one directional. This fits exactly what I need because the browser is just waiting for events. However, there are rare cases when the user can send data. Is there an alternative to Server Side Events, where I can keep a connection open to send data back to the server? Is it better to use SSE + AJAX, SSE + (Alternative Way), or just a web socket (Even though data is rarely sent back to server)?

Thank you

Answer 1

This is the best explanation for SSE and its flexibilty

Server-Sent Events vs. WebSockets

Why would you choose Server-Sent Events over WebSockets? Good question.

One reason SSEs have been kept in the shadow is because later APIs like WebSockets provide a richer protocol to perform bi-directional, full-duplex communication. Having a two-way channel is more attractive for things like games, messaging apps, and for cases where you need near real-time updates in both directions. However, in some scenarios data doesn't need to be sent from the client. You simply need updates from some server action. A few examples would be friends' status updates, stock tickers, news feeds, or other automated data push mechanisms (eg updating a client-side Web SQL Database or IndexedDB object store). If you'll need to send data to a server, XMLHttpRequest is always a friend.

SSEs are sent over traditional HTTP. That means they do not require a special protocol or server implementation to get working. WebSockets on the other hand, require full-duplex connections and new Web Socket servers to handle the protocol. In addition, Server-Sent Events have a variety of features that WebSockets lack by design such as automatic reconnection, event IDs, and the ability to send arbitrary events.

I had built a chat application using sse and ajax for my site.I would suggest sse + ajax would be way to go if there is only stream updates and very few updates from client to server for that you can use the ajax part

Only problem that I found is its lack of support across browsers .And if you want to know more in depth about sse ask specifically what you want

Browser Support List

Answer 2

As you usage is mostly server pushing to client, I would recommend a combination of Server-Sent events for the push from server to client and AJAX for the other way around.

You should definitely read this article to get to a decision:

http://streamdata.io/blog/push-sse-vs-websockets/

This will give you pros and cons of using Server-Sent events versus WebSocket.