WebSockets vs. Webhooks

WebSockets and webhooks are important communication technologies used in modern applications. While both are used for web communication and are likely to be part of the same site or app, they operate in distinct ways with different use cases.

What Are WebSockets?

The WebSocket protocol is a communication protocol for bidirectional communication between clients and servers over a persistent TCP connection in real time.

Unlike HTTP, which is request-response oriented, WebSockets allows clients and servers to exchange messages freely in either direction. Achieving something similar with HTTP requires polling, which comes with a higher overhead.

WebSockets' persistent connection enables instant data transfer and works well when low-latency transfer is required, such as real-time communication applications, streaming live data, and collaboration platforms.

If you've ever played a browser-based game with a live leaderboard, the developers likely used WebSockets to update high-score player rankings.

How Do WebSockets Work?

A WebSocket connection starts with a handshake over an active TCP connection.

A client sends an HTTP/HTTPS GET request to a server, typically over the standard ports 80 for HTTP and 443 for HTTPS. The request may look like:

GET /game/highscore HTTP/1.1
Host: supercoolgame.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: (some key value)
Sec-WebSocket-Version: 13

The upgrade and connection headers indicate the request to upgrade from HTTP/HTTPS to a WebSocket connection. The Sec-WebSocket-Key and Sec-WebSocket-Version headers are also required for security purposes.

Once the server receives the request, it sends an HTTP 101 status code and matching Upgrade/Connection headers. This confirms that the server is switching from HTTP to a full-duplex WebSocket connection over a persistent TCP link. It may look like this:

HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: (different key value based on Sec-WebSocket-Key value and the protocol's hardcode globally unique identifier (GUID))

If the handshake completes successfully, the client and server can communicate using the WebSocket protocol. No requests or responses are needed.

The data servers and clients send each other are known as messages. They can be data messages for sending text or binary data, or they can be control messages for signaling information about the connection.

These messages are fragmented into small frames, allowing larger messages to be split across multiple frames for smoother transmission.

A frame consists of:

• A header, which includes information like opcode, message length, and fragmentation details.
• A payload, which contains the actual data. 

Servers and Clients in WebSockets

Every implementation of WebSockets will differ depending on the app's or site's use case, but they all contain the same two basic building blocks: a server and a client.

Developers have an abundance of choices for building both.

For creating the server, Node.js is likely the most common, although you can also work with Python (Django Channels or the websockets library), Java (Spring Boot), Go (gorilla/websocket), and many other languages.

Your server will need a way to listen for the connection, including setting the port on which it listens. You'll also configure it to handle connection events, incoming messages, authentication, errors, closing connections, and more.

You'll need to program the client connection, which is usually written in JavaScript.

Your client must be able to send messages to the server and listen to messages from the server, as well as handle the connection and disconnection process.

Some tools can simplify this workflow, like the open-source library Socket.IO. It provides both client- and server-side components and features for reconnection and maintaining the connection state.

What Are Webhooks?

A webhook is a lightweight, event-driven mechanism that enables one system to send real-time data to another automatically via HTTP.

In simple terms, webhooks act as "callbacks" that are triggered when a specific event occurs in a source system. This is why they're sometimes called reverse APIs --- instead of your system calling an external one (the API), the external system calls yours.

Like WebSockets, webhooks eliminate the need for HTTP polling and reduce overhead. However, they use a simple, one-way push of data instead of maintaining a continuous, two-way communication flow, further reducing overhead.

They're commonly used for integrating applications, automating event-driven workflows, and server-to-server notifications.

For example, a live streaming app may use webhooks when a user donates to a streamer to initiate actions like "thank you" animations and receipt emailing.

How Do Webhooks Work?

A webhook has three main parts:

• Event: The action that triggers the webhook, such as a user subscribing to a service, sending a payment, or updating the details of an account.
• Payload: The data carried by the webhook, which also contains details about the event. It may include user information and other metadata that the recipient uses to act upon the event.
• Endpoint: The URL that receives the webhook and processes the data.

Let's examine these parts using our live-streaming thank-you animation example.

When a viewer donates $10 USD to a streamer, the system immediately triggers a webhook.

The system handling donations sends an HTTP POST request to the webhook endpoint, containing metadata in the headers and the payload data in the request's body. The payload data would likely be in JSON format and might contain information like the viewer's username, the donation amount, and a timestamp.

The HTTP request headers may look like this:

POST /livestreaming-app/webhooks/donations HTTP/1.1
Host: livestreaming-app.example.com
Content-Type: application/json
Content-Length: (size of the request measured in bytes)

The payload would look something like this:

{
  "event": "donation.success",
  "data": {
    "username": "YourBiggestFan",
    "amount": 10
  }
}

Upon receiving the request, the application server authenticates it with a predefined method, such as secret tokens. The server then parses the payload to make sure the donation payment went through.

If the request is successful and the event type matches ("donation.success" instead of "donation.failure" in our scenario), the server executes the business logic of the webhook by playing the thank you animation on screen.

After processing the webhook, the server responds with a 200 OK status code to indicate success and prevent the sender from retrying the request.

How Developers Create Webhooks

Webhooks have a simpler workflow compared to WebSockets.

As a developer, you'd need to:

1. Create and secure a webhook endpoint. Set up an HTTP endpoint on your server to accept incoming requests. Using HTTPS can make sure data is more securely transmitted.
2. Validate the incoming data. Parse the incoming HTTP header and body and verify the request using a security method like signatures, shared secrets, or authentication tokens.
3. Process payload. Retrieve the payload data and perform your desired actions, such as updating a database, sending a notification, or triggering another workflow. Afterward, respond to the request with the appropriate HTTP status code.
4. Testing the endpoint and registering the webhook. Test the endpoint to make sure it receives, authenticates, and processes data as expected. If successful, you can register it to a third-party service (like a payment platform), so that service knows where to send the data.

How Do WebSockets and Webhooks Differ?

WebSockets and webhooks are similar in that they're both:

• Alternatives for HTTP polling with lower overhead
• Often used in modern websites and web apps for real-time data delivery
• Event-driven
• Contain "web" in the name

This is largely where their similarities end.

They differ in the following ways:

• Communication pattern: WebSockets are bidirectional and persistent between a client and a server, although communication between two servers is possible. Webhooks are unidirectional, with a TCP connection only opening and closing to send a payload from one server to another.
• Connection type: Webhooks use HTTP to send payloads. Beyond the initial upgrade HTTP request, WebSockets exchange data directly over TCP.
• Complexity: WebSockets are more complex to implement due to their stateful, persistent connection and requiring more complicated business logic to handle interactions client- and server-side. Webhooks are stateless, HTTP-based, and simpler to program.
• Scalability: Webhooks are easier to scale since each event is a separate, stateless call. WebSockets' multiple persistent connections generate more overhead and require more active management.
• Classification: Webhooks are user-defined methods. WebSockets are a protocol.

When To Use WebSockets vs. Webhooks

WebSockets are ideal when data needs to flow in both directions and the connection needs to remain active.

You will likely use WebSockets for building the following:

• Real-time chat: WebSockets enable instant messaging in dedicated chat applications or in-app messaging in other apps, providing quicker message exchange than HTTP polling or other communication protocols like BOSH.
• Social media: In social apps, they enable real-time interactions such as dynamic content updates, live notifications, live activity indicators, and more.
• Online gaming: They provide a smooth player experience in online games, including character movement, matchmaking, and scoreboard updates.
• Team collaboration platforms: They're integral to collaboration tools that require real-time data synchronization among multiple users. WebSockets allow several users to edit documents or designs simultaneously, reflecting changes instantly across all devices.
• Live dashboards: Trading applications, logistics systems, IoT device dashboards, and similar use WebSockets to provide real-time updates on important data, allowing users to make timely decisions based on accurate information.

When you only need data to flow in one direction based on specific triggers, you would implement webhooks instead.

Webhooks are better suited for use cases like:

• Marketplace and payment processing: Webhooks enable different systems involved in marketplace operations and payment processing to work seamlessly. They can be set up to update inventory management systems, send emails to users for new orders or payment confirmation, and more.
• Live events: During live events, webhooks can enhance attendee engagement with uses like sending notifications to attendees about schedule changes or updates, informing participants in real-time.
• Delivery and mobility apps: They can facilitate updates in delivery and mobility apps for order statuses, service changes, driver locations, and more.
• Third-party integrations: Many platforms like Slack, GitHub, and Stripe provide webhooks for users to integrate into their own apps. For example, when a Stripe payment is made, it pushes data to your registered endpoint, which you can use for purposes like updating user information or databases or sending emails with transaction information.

Despite having different use cases, they can complement each other, and you'll likely use both at some point when building a project or product.

For example, you might build a chat application in React using WebSockets for the main chat function. You could then set up webhooks to integrate third-party APIs like the Google Calendar API, allowing users to post Google Calendar events directly into the chat.

Frequently Asked Questions