websocket vs server sent events

src: WebSockets vs. Server-Sent Events | Bits and Pieces - 2022-07-04

Abstract

• WebSockets: WebSockets are widely used and valued in technological solutions such as real-time polling, chat, media players, multiplayer games, etc.
• Server-Sent Events: There are many applications where sending data from the client isn’t necessary. SSEs are especially useful in status updates, social-media news feeds, push notifications, newsletters, etc.

Over the years, the HTTP request-response model has been used for client-server communications in web applications. However, with the popularity of real-time web applications, the need has emerged for servers to be able to push data to clients proactively without having clients requesting it first.

As a result, push technology-based communication methods like WebSockets, and Server-Sent Events (SSE) became popular among developers. These methods are internet-based communication types where the server initiates the request for a particular transaction.

So, this article will compare and contrast WebSockets and Server-Sent Events to help you choose the best one for your project.

websocket

WebSockets is an advanced technology that enables bidirectional real-time interactive communication between a client and a server.

It is achieved by defining a standardized mechanism for the server to send data to the client without the client first making a request. After the first message, the connection will be kept open, allowing the client and the server to have continuous two-way communication without any interruptions.

WebSockets use the WebSocket protocol for communication. A WebSocket connection begins as a regular HTTP connection, which gets modified to a WebSocket connection via the WebSocket handshake. The handshake begins with a client sending an HTTP request with a special UPGRADE header. The server then receives the request, processes it, and switches to the WebSocket protocol if the request is accepted. Bidirectional communication is possible when this handshake is completed.

Advantages

• WebSockets allow real-time bidirectional communication.
• Since WebSockets don’t typically employ ‘XMLHttpRequest,’ headers aren’t supplied when we need further server data. As a result, the heavy data loads transmitted to the server are reduced.
• WebSockets allow you to send data in binary and UTF-8 text formats. Sending data in binary format can improve the efficiency of data transmission and interpretation because all values of a byte can be used in the encoding.
• WebSockets support browsers such as Google Chrome, Microsoft Edge, Opera, Firefox, Safari, and others
• WebSockets can identify a terminated client connection.
• WebSockets are highly robust since they can manage extensive projects.

Potential Drawbacks

WebSockets have one significant disadvantage. They do not entirely operate on top of HTTP. Instead, they need their TCP connection to work. They merely need HTTP to initiate the connection and then upgrade it to a standalone TCP connection used with the WebSocket protocol.

It may not seem like a significant concern, but it implies that WebSockets are unable to take advantage of any HTTP functionality:

• There is no compression support.
• HTTP/2 multiplexing is not supported.
• Proxies may cause problems.
• Vulnerable to Cross-Site Hijacking.

Also,

• Setting up WebSockets is more complex and time-consuming because it necessitates a significant amount of upfront work.
• WebSocket connections were not supported in browsers earlier than 2011.
• WebSockets do not automatically recover with closed connections. This must be performed manually.
• WebSockets are problematic for some enterprise firewalls with packet monitoring (notably SophosXG Firewall, WatchGuard, McAfee Web Gateway).

server sent events

SSE (Server-Sent Events) is a technique that allows a browser (client) to receive automatic updates from a server, such as text-based event data, over a standard HTTP connection.

The goal of SSE is to give the browser a smooth way to receive data from the server without having to ask for it. It’s a specification that defines how servers start sending data to clients after establishing a client connection. To optimize cross-browser streaming, they employ a JavaScript API called EventSource to register with the event source and transmit messages or continuous updates to a client. Throughout event initialization, the event source will be supplied to EventSource API. It will control the connection to the source and automatically send changes to clients. This concept makes working with real-time data extremely efficient as it only utilizes one long-lasting HTTP connection.

Advantages

• Instead of using a custom protocol, data is sent over HTTP.
• SSE can be “backported” to browsers that don’t support it yet by poly filling it with JavaScript.
• Built-in capability for reconnection (when the server drops or closes the connection, the client will automatically attempt to reconnect without any user involvement.)
• Packet monitoring is not a problem for enterprise firewalls.
• Mozilla, Chrome, and Safari are the browsers that SSEs support.
• SSE is faster and more convenient to set up than WebSockets.

Potential Drawbacks

• SSE can only handle UTF-8 characters and does not support binary data.
• In terms of the maximum number of open connections, SSE has restrictions. However, the limit is per browser and set to a low value. This situation will lead to an unpleasant experience when opening multiple tabs.
• SSE is a one-way technique and does not allow for bidirectional data transmission.
• In SSE, browser support is limited.

websocket and server sent events: Similarities

You must have noticed some similarities between the two technologies we have discussed so far, besides the fact that they both use HTTP connections. The most apparent similarity is that they both work precisely the same way. For example, they use a procedure known as server push to send data from the server to the client.

websocket and server sent events: Differences

The significant difference between both technologies is that WebSockets are bidirectional while SSEs are mono-directional.

So, if you’re eager to add server push functionality to your app, they’re both viable options to explore. On the other hand, WebSockets will better fulfill your demands if you’re looking for a bi-directional communication method.

When it comes to extensibility, WebSockets are far more complicated and time-consuming to set up than SSEs. Nevertheless, they create a very reliable and extensible application environment. On the other hand, SSE is a more straightforward and faster approach, but it lacks extensibility. For example, if your web application’s requirements are revised, you’ll have to refactor it using WebSockets, which are more flexible and capable of handling complex projects.

Use Cases

WebSockets: WebSockets are widely used and valued in technological solutions such as real-time polling, chat, media players, multiplayer games, etc.

Server-Sent Events: There are many applications where sending data from the client isn’t necessary. SSEs are especially useful in status updates, social-media news feeds, push notifications, newsletters, etc.

Conclusion

This article highlighted the specific advantages and drawbacks of the two technologies, WebSockets and SSEs, by comparing and contrasting them. Now that you have a better understanding of them, you can decide on the better one for your needs. However, it’s important to note that they’re not rival technologies, and none is superior to the other. Whether you should utilize WebSockets or SSEs is a matter of personal preference.