How do you quickly close a nonresponsive websocket in Java Spring Tomcat?

Question

I have a real-time application with clients using websockets to connect with a Spring Framework server, which is running Spring Boot Tomcat. I want the server to quickly (within 5 seconds) detect when a client stops responding due to a network disconnect or other issue and close the websocket.

I have tried

1. Setting the max session idle timeout as described in the documentation as "Configuring the WebSocket Engine" http://docs.spring.io/spring/docs/current/spring-framework-reference/html/websocket.html

   @Bean
   public WebSocketHandler clientHandler() {
       return new PerConnectionWebSocketHandler(ClientHandler.class);
   }
   @Bean
   public ServletServerContainerFactoryBean createWebSocketContainer() {
       ServletServerContainerFactoryBean container = 
           new ServletServerContainerFactoryBean();
       container.setMaxSessionIdleTimeout(5000);
       container.setAsyncSendTimeout(5000);
       return container;
   }
   

I am not sure this is implemented correctly because I do not see the link between the ServletServerContainerFactoryBean and my generation of ClientHandlers.

2. Sending ping messages from server every 2.5 seconds. After I manually disconnect the client by breaking the network connection, the server happily sends pings for another 30+ seconds until a transport error appears.

3. 1 and 2 simultaneously

4. 1 and 2 and setting server.session-timeout = 5 in application.properties

My methodology for testing this is to:

1. Connect a websocket from a laptop client to the Tomcat server
2. Turn off network connection on the laptop using the physical switch
3. Wait for Tomcat server events

How does a Spring FrameworkTomcat server quickly detect that a client has been disconnected or not responding to close the websocket?

Answer 1

The approach I eventually took was to implement an application-layer ping-pong protocol.

• The server sends a ping message with period p to the client.
• The client responds to each ping message with a pong message.
• If the server sends more than n ping messages without receiving a pong response, it generates a timeout event.
• The client can also generate a timeout event if it does not receive a ping message in n*p time.

There should be a much simpler way of implementing this using timeouts in the underlying TCP connection.