WebSocket Connection Made Easy: A Step-by-Step Guide by Sato Kenta

November 14, 2022 davidhenson

You might try using one of the out-of-the-box solutions such as Socket.IO, Atmosphere, any JSR 356-equipped application server, SignalR, or Kaazing but how can you tell which of these will work best for you? What will you have to build yourself, what might you have to buy, and what doe you need to look out for? In this session, we’ll put WebSocket under the microscope, then look at it in multiple real-world deployments.

The essence of WebSocket’s headers extends beyond initial link setup; it is also fundamental for testing WebSocket APIs. With a solid grasp on the mechanics of WebSocket exchanges, you can advance to validating your APIs, ensuring they operate as anticipated. In particular, codes lower than 1000 are reserved, there’ll be an error if we try to set such a code. But the data will be buffered (stored) in memory and sent out only as fast as network speed allows.

Installing dependencies and initializing a WebSocket server in Node.js

In the event that connection to a server was slow, we’d want to consider moving the call to onConnect inside of the event listener callback for the open event up above. Though not necessary in a technical sense, these are important to have for communicating back to yourself (and other developers) that a connect was successful, or, that a connection was lost. The latter scenario occurs when a websocket server becomes unreachable or intentionally closes the connection to the client.

The
connection is encrypted with TLS (Transport Layer Security). The WebSocket object provides the API for creating and managing a WebSocket connection to a server, as well as for sending and receiving data on the connection. WebSockets are one of the most interesting and convenient ways to achieve real-time capabilities in a modern application.

Step 2: Define WebSocket API Details

Here Sec-WebSocket-Accept is Sec-WebSocket-Key, recoded using a special algorithm. Upon seeing it, the browser understands that the server really does support the WebSocket protocol. Let’s change the previous example to send the same timestamps to all browsers,
instead of generating independent sequences for each client.

We can perform custom logic based on the received message, such as updating the application state, broadcasting the message to other connected clients, or triggering specific actions.
JavaScript Object Notation (JSON) is a widely used data interchange format that provides a simple and human-readable way to represent structured data.
Here, we pass in our message as part of an object and expect .send() to convert that to a string before sending it up to the server.
As usual, it may also give the reason why the handshake failed in the HTTP response body, but the message may never be displayed (browsers do not display it).
Depending on your platform, this may be handled for you automatically.

It’s the gold standard for high-performance networking in your hand from managing high-speed trains to tracking live sporting events. It’s seen deployment in application servers (NodeJS, Tomcat, Glassfish, Jetty, etc.) and all major browsers. And yet, developers still run into challenges when moving from HTTP to WebSocket. They’re puzzled at the best ways to ensure performance, compatibility, connectivity, and security.

Broadcast messages#

But the user has a slow network connection, maybe on a mobile internet, outside of a city. For demo purposes, there’s a small server server.js written in Node.js, for the example above, running. It responds with “Hello from server, John”, then waits 5 seconds and closes the connection. It may be helpful to examine the socket’s bufferedAmount attribute before attempting to close the connection to determine if any data has yet to be transmitted on the network. If this value isn’t 0, there’s pending data still, so you may wish to wait before closing the connection.

Though some servers accept a short Sec-WebSocket-Key, many modern servers will reject the request with error “invalid Sec-WebSocket-Key header”. Sec-WebSocket-Key and Sec-WebSocket-Accept are intended to prevent a caching proxy from re-sending a previous WebSocket conversation,[39] and does not provide any authentication, privacy, or integrity. Although they are different, RFC 6455 states that WebSocket “is designed to work over HTTP ports 443 and 80 as well as to support HTTP proxies and intermediaries”, thus making it compatible with HTTP. To achieve compatibility, the WebSocket handshake uses the HTTP Upgrade header[3] to change from the HTTP protocol to the WebSocket protocol. Manage file uploads in your Next.js app using UploadThing, a file upload tool to be used in full-stack TypeScript applications.

Opening handshake

There were a lot of loopholes in long polling — header overhead, latency, timeouts, caching, and so on. If an error occurs during the API request or data retrieval, an error is thrown and logged to the console. The fetchRealTimeData function is an async function that uses the axios library to make an HTTP GET request to the Alpha Vantage API. We create an HTTP server using http.createServer() and initialize Socket.IO with the created server using socketIO(server). Here, we are creating a WebSocket server that will listen on port 8080.

When the ping is received, the recipient must send back a pong as soon as possible. You can use this to make sure that the client is still connected, for example. Encountering “WebSocket Connection Failed” messages can stump web development efforts. Numerous factors, from network hiccups to SSL/TLS setup woes, server misconfiguration, mismatched protocols, security restrictions, how does websocket work bugs, CORS conflicts, or resource overloads, may impede your connection’s efficacy. Normally, when a party wants to close the connection (both browser and server have equal rights), they send a “connection close frame” with a numeric code and a textual reason. Here the server responds that it supports the extension “deflate-frame”, and only SOAP of the requested subprotocols.

WebSocket in the Real World

Just don’t forget to install Node.js and npm install ws before running. The socket.bufferedAmount property stores how many bytes remain buffered at this moment, waiting to be sent over the network. In the browser, we directly work only with text or binary frames. Visit Mozilla Corporation’s not-for-profit parent, the Mozilla Foundation.Portions of this content are ©1998–2024 by individual mozilla.org contributors. Here we use JSON.parse() to convert the JSON object back into the original object, then examine and act upon its contents.

Learn more about the SSE architecture from this GitHub Gist file. The code that went into them appeared as a workaround to make a request-reply-type protocol full-duplex-like. This mechanism saved the pain of network latency because the initial request is kept open indefinitely. The request is never terminated, even after the server pushes the data.

This enables targeted message broadcasting and efficient data management. When receiving messages from clients, you will need to deserialize the received JSON string to access and process the data. In the first event listener, connection, we can define the logic to handle new WebSocket connections. This code block will be executed each time a client establishes a WebSocket connection with the server.