Connecting to a Broker

A STOMP broker relay maintains a single “system” TCP connection to the broker. This connection is used for messages originating from the server-side application only, not for receiving messages. You can configure the STOMP credentials (that is, the STOMP frame login and passcode headers) for this connection. This is exposed in both the XML namespace and Java configuration as the systemLogin and systemPasscode properties with default values of guest and guest.

The STOMP broker relay also creates a separate TCP connection for every connected WebSocket client. You can configure the STOMP credentials that are used for all TCP connections created on behalf of clients. This is exposed in both the XML namespace and Java configuration as the clientLogin and clientPasscode properties with default values of guest and guest.

The STOMP broker relay always sets the login and passcode headers on every CONNECT frame that it forwards to the broker on behalf of clients. Therefore, WebSocket clients need not set those headers. They are ignored. As the Authentication section explains, WebSocket clients should instead rely on HTTP authentication to protect the WebSocket endpoint and establish the client identity.

The STOMP broker relay also sends and receives heartbeats to and from the message broker over the “system” TCP connection. You can configure the intervals for sending and receiving heartbeats (10 seconds each by default). If connectivity to the broker is lost, the broker relay continues to try to reconnect, every 5 seconds, until it succeeds.

Any Spring bean can implement ApplicationListener<BrokerAvailabilityEvent> to receive notifications when the “system” connection to the broker is lost and re-established. For example, a Stock Quote service that broadcasts stock quotes can stop trying to send messages when there is no active “system” connection.

By default, the STOMP broker relay always connects, and reconnects as needed if connectivity is lost, to the same host and port. If you wish to supply multiple addresses, on each attempt to connect, you can configure a supplier of addresses, instead of a fixed host and port. The following example shows how to do that:

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer {

	// ...

	@Override
	public void configureMessageBroker(MessageBrokerRegistry registry) {
		registry.enableStompBrokerRelay("/queue/", "/topic/").setTcpClient(createTcpClient());
		registry.setApplicationDestinationPrefixes("/app");
	}

	private ReactorNettyTcpClient<byte[]> createTcpClient() {
		return new ReactorNettyTcpClient<>(
				client -> client.addressSupplier(() -> ... ),
				new StompReactorNettyCodec());
	}
}

You can also configure the STOMP broker relay with a virtualHost property. The value of this property is set as the host header of every CONNECT frame and can be useful (for example, in a cloud environment where the actual host to which the TCP connection is established differs from the host that provides the cloud-based STOMP service).