How to get the cipher suite being used in HiveMQ Client?

Question

I configured the HiveMQ server to recognize TLS and created a TLS communication. I'd like to print out the cipher suites being used. I've used the getSslConfig() but I end up getting this as an output:

Optional[com.hivemq.client.internal.mqtt.MqttClientSslConfigImpl@2710]

I'm aware there is a getCipherSuites() method in MqttClientSslConfig.java but I haven't been able to find a way to use it. As a follow up how would I specify a particular cipher suite be used? So far I've just been using the default one like so:

Code (How to specify a particular cipher suite?):

Mqtt5BlockingClient subscriber = Mqtt5Client.builder()
        .identifier(UUID.randomUUID().toString()) // the unique identifier of the MQTT client. The ID is randomly generated between 
        .serverHost("localhost")  // the host name or IP address of the MQTT server. Kept it localhost for testing. localhost is default if not specified.
        .serverPort(8883)  // specifies the port of the server
        .addConnectedListener(context -> ClientConnectionRetreiver.printConnected("Subscriber1"))        // prints a string that the client is connected
        .addDisconnectedListener(context -> ClientConnectionRetreiver.printDisconnected("Subscriber1"))  // prints a string that the client is disconnected
        .sslWithDefaultConfig()  // << How can I specify a particular cipher suite?
        .buildBlocking();  // creates the client builder

Code (How I've been trying to get the SSL config) :

Mqtt5ClientConfig clientConfig = client.getConfig();
System.out.println(" Ssl Configuration: " + clientConfig.getSslConfig());

Answer 1

You can configure a specific cipher suite like so:

Mqtt5Client.builder()
        ...
        .sslConfig()
            .cipherSuites(Arrays.asList("TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256"))
            .applySslConfig()
        ...

getSslConfig returns an Optional . So to get the cipher suites:

client.getConfig().getSslConfig().get().getCipherSuites()