WebSocket Chat Application in Spring Boot Not Receiving Messages in Postman

CONNECT
accept-version:1.2
heart-beat:10000,10000

\0

SEND
destination:/app/chat.sendMessage
content-type:application/json

{
  "senderId": 10000,
  "recipientId": 10002,
  "content": "Hello, World!",
  "isPrivate": true
}\0

CONNECT
accept-version:1.2
heart-beat:10000,10000

\0

SUBSCRIBE
id:sub-0
destination:/user/10002/queue/messages

\0

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {

    @Override
    public void configureMessageBroker(MessageBrokerRegistry config) {
        config.enableSimpleBroker("/topic", "/queue");
        config.setApplicationDestinationPrefixes("/app");
        config.setUserDestinationPrefix("/user");
    }

    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/ws/{matricule}")
                .setAllowedOrigins("*")
                .withSockJS();
    }
}

public class HandshakeInterceptor extends HttpSessionHandshakeInterceptor {

    @Override
    public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Map<String, Object> attributes) throws Exception {
        String path = request.getURI().getPath();
        Long matricule = Long.parseLong(path.substring(path.lastIndexOf('/') + 1));
        attributes.put("matricule", matricule);
        return super.beforeHandshake(request, response, wsHandler, attributes);
    }
}

@Component
public class TradeWebSocketHandler extends TextWebSocketHandler {

    private final Map<Long, WebSocketSession> sessions = new HashMap<>();
    private final ObjectMapper objectMapper = new ObjectMapper();

    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        Long matricule = (Long) session.getAttributes().get("matricule");
        sessions.put(matricule, session);
        System.out.println("Connected: " + matricule);
    }

    @Override
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
        String payload = message.getPayload();
        System.out.println("Received: " + payload);

        // Parse the message
        ChatMessageDTO chatMessageDTO = objectMapper.readValue(payload, ChatMessageDTO.class);

        // Get the recipient's session
        WebSocketSession recipientSession = sessions.get(chatMessageDTO.recipientId());
        if (recipientSession != null && recipientSession.isOpen()) {
            recipientSession.sendMessage(new TextMessage(payload));
        }
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
        Long matricule = (Long) session.getAttributes().get("matricule");
        sessions.remove(matricule);
        System.out.println("Disconnected: " + matricule);
    }
}