spring websocket cannot establish connection

cannot establish connection to my websocket server by browser client.

configuration:

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer {

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

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


}

And controller:

@MessageMapping("/message")
@SendToUser("/queue/reply")
public String processMessageFromClient(@Payload String message, Principal principal) throws Exception {
	String name = new Gson().fromJson(message, Map.class).get("name").toString();
	System.out.println(name);
	//messagingTemplate.convertAndSendToUser(principal.getName(), "/queue/reply", name);
	return name;
}

I start server, and then open index.html in browser then make connect to ws://localhost:8080/greeting
and after that sending message to /app/message

but actually happens nothing. Browser inspector shows 404. What's wronng i do?

Here is the way that use to implement WebSocket in Spring. First, you should configure the Web socket message broker and register the stomp endpoint as below. Here I use setAllowedOrigins("*").withSockJS() to access this endpoint to any host.

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer {
    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/greeting")
                .setAllowedOrigins("*")
                .withSockJS();
    }
    @Override
    public void configureMessageBroker(MessageBrokerRegistry registry) {
        registry.setApplicationDestinationPrefixes("/app")
                .enableSimpleBroker("/topic", "/queue/");
    }
}

Then I create the controller as below.

@Controller
public class WebSocketController {

    private final SimpMessagingTemplate template;

    @Autowired
    WebSocketController(SimpMessagingTemplate template){
        this.template = template;
    }

    @MessageMapping("/queue/reply")
    public void sendMessage(String message){
        System.out.println(message);
        this.template.convertAndSend("/topic",  message);
    }
}

Use @MessageMapping("/queue/reply") instead of @SendToUser("/queue/reply") as above.

> From that Simple Messaging Template, I used convertAndSend() method to
> asynchronous data communication with that message broker. If there is
> any data comes to that message broker it will automatically send that
> data using the above configured endpoint called /socket with SockJS
> and Stomp.

You can refer this article to learn more about the Spring web socket.