Create a Simple Chat Application Using Socket.IO in Java

A detailed guide on how to create a simple chat application using Java and Socket.IO. This article will help you understand how to set up a server and client for real-time communication.

This article will guide you in building a simple chat application using Socket.IO in Java. We will set up a server using Spring Boot and a client using Java Swing to create a user interface. The application will allow users to send and receive messages in real-time.

Java Code

1. Setting up the server with Spring Boot

// build.gradle
plugins {
    id 'org.springframework.boot' version '3.0.0'
    id 'io.spring.dependency-management' version '1.0.12.RELEASE'
    id 'java'
}

group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '17'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-websocket'
    implementation 'org.springframework.boot:spring-boot-starter'
}

tasks.named('test') {
    useJUnitPlatform()
}

// WebSocketConfig.java
import org.springframework.context.annotation.Configuration;
import org.springframework.messaging.simp.config.MessageBrokerRegistry;
import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
    @Override
    public void configureMessageBroker(MessageBrokerRegistry config) {
        config.enableSimpleBroker("/topic");
        config.setApplicationDestinationPrefixes("/app");
    }

    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/chat").withSockJS();
    }
}

// ChatController.java
import org.springframework.messaging.handler.annotation.MessageMapping;
import org.springframework.messaging.simp.SimpMessagingTemplate;
import org.springframework.stereotype.Controller;

@Controller
public class ChatController {
    private final SimpMessagingTemplate messagingTemplate;

    public ChatController(SimpMessagingTemplate messagingTemplate) {
        this.messagingTemplate = messagingTemplate;
    }

    @MessageMapping("/send")
    public void sendMessage(String message) {
        messagingTemplate.convertAndSend("/topic/messages", message);
    }
}

2. Setting up the client with Java Swing

import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import org.java_websocket.client.WebSocketClient;
import org.java_websocket.handshake.ServerHandshake;

public class ChatClient extends WebSocketClient {
    private JTextArea textArea;
    private JTextField textField;

    public ChatClient(String serverUri, JTextArea textArea, JTextField textField) {
        super(new URI(serverUri));
        this.textArea = textArea;
        this.textField = textField;
    }

    @Override
    public void onOpen(ServerHandshake handshakedata) {
        System.out.println("Connected to server");
    }

    @Override
    public void onMessage(String message) {
        textArea.append(message + "\n");
    }

    @Override
    public void onClose(int code, String reason, boolean remote) {
        System.out.println("Disconnected from server");
    }

    @Override
    public void onError(Exception ex) {
        ex.printStackTrace();
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Chat Application");
        JTextArea textArea = new JTextArea(20, 30);


        JTextField textField = new JTextField(30);
        JButton sendButton = new JButton("Send");

        frame.getContentPane().add(new JScrollPane(textArea), "Center");
        frame.getContentPane().add(textField, "South");
        frame.getContentPane().add(sendButton, "South");

        ChatClient client = new ChatClient("ws://localhost:8080/chat", textArea, textField);
        client.connect();

        sendButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String message = textField.getText();
                client.send(message);
                textField.setText("");
            }
        });

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }
}

Detailed explanation:

1. Server:

   • WebSocketConfig: Configures WebSocket with Spring Boot, enabling STOMP for message sending.
   • ChatController: Receives and processes messages sent from the client, broadcasting to all connected clients.

2. Client:

   • ChatClient: Connects to the WebSocket server and manages sending and receiving messages. Uses Java Swing to create the user interface for the chat application.

System Requirements:

• Java 17 or higher
• Spring Boot 3.0 or higher
• WebSocket library

How to install the libraries needed to run the Java code above:

Use Gradle for dependency management. Run the command gradle build in the directory containing build.gradle to install the required libraries.

Tips:

• Make sure the server is running before starting the client.
• Explore STOMP further to expand the features of your chat application.

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