How do you handle message broadcasting in WebSocket applications?

Table of Contents

• Introduction
• Steps to Handle Message Broadcasting in WebSocket Applications
  • 1. Add Dependencies to pom.xml (Maven)
  • 2. Create WebSocket Configuration
    • Example: WebSocket Configuration
  • 3. Create WebSocket Controller for Broadcasting
    • Example: WebSocket Controller with Broadcasting
  • 4. Create a WebSocket Client (HTML + JavaScript)
    • Example: WebSocket Client
  • 5. Running the Application
• Conclusion

Introduction

In WebSocket applications, broadcasting messages refers to sending a message from the server to multiple clients simultaneously. This is especially useful in scenarios like chat applications, live updates, or notifications where messages need to be sent to many connected clients at once. Spring Boot, combined with STOMP (Simple Text Oriented Messaging Protocol), offers an easy and effective way to implement message broadcasting in WebSocket applications. In this guide, we will walk through how to broadcast messages to multiple WebSocket clients using Spring Boot and STOMP.

Steps to Handle Message Broadcasting in WebSocket Applications

1. Add Dependencies to pom.xml (Maven)

Before implementing broadcasting, you need to include the necessary dependencies for WebSocket support and messaging in Spring Boot.

For Gradle users, you can include the following dependencies:

These dependencies enable WebSocket communication and STOMP messaging in your Spring Boot application.

2. Create WebSocket Configuration

Before implementing broadcasting, you need to configure WebSocket and STOMP messaging in your Spring Boot application. The configuration includes setting up message brokers and WebSocket endpoints.

Example: WebSocket Configuration

• @EnableWebSocketMessageBroker: Enables WebSocket message handling with STOMP.
• configureMessageBroker: Configures a message broker with the prefix /topic for broadcasting messages to clients.
• registerStompEndpoints: Registers the /ws endpoint that clients will connect to.

3. Create WebSocket Controller for Broadcasting

The WebSocket controller is responsible for handling messages and broadcasting them to clients. The server sends messages to all clients that are subscribed to a specific topic.

Example: WebSocket Controller with Broadcasting

In this controller:

@MessageMapping("/send"): This annotation listens for messages sent to the /app/send destination (the clients send messages here).

• SimpMessagingTemplate: This template is used to send the message to all clients subscribed to the /topic/messages destination.

4. Create a WebSocket Client (HTML + JavaScript)

The client-side application connects to the WebSocket server, sends messages, and subscribes to a topic to receive broadcasted messages.

Example: WebSocket Client

In this client:

• SockJS: Provides fallback support for browsers that do not support WebSockets natively.
• STOMP: Used for handling messaging. The client connects to /ws, subscribes to the /topic/messages destination, and sends messages to the /app/send destination.
• sendMessage(): Sends the message entered by the user to the server, where it will be broadcasted to all clients.

5. Running the Application

1. Start the Spring Boot application: Run the application using mvn spring-boot:run (for Maven) or gradle bootRun (for Gradle).
2. Open multiple clients: Open the HTML file in multiple browser tabs to simulate multiple clients.
3. Test the broadcast: Enter a message in one tab and click "Send". The message should be broadcasted to all other connected clients in real-time.

Conclusion

Message broadcasting in WebSocket applications with Spring Boot allows you to send messages from the server to multiple clients simultaneously. Using STOMP over WebSocket, you can easily broadcast messages to clients subscribed to a specific topic. By implementing a WebSocket controller and using SimpMessagingTemplate, Spring Boot simplifies the process of real-time messaging and broadcasting. This is particularly useful for applications like live chat, notifications, and real-time data feeds.