open fun publish(topic: String, payload: Buffer, qosLevel: MqttQoS, isDup: Boolean, isRetain: Boolean): MqttEndpoint
Sends the PUBLISH message to the remote MQTT client
topic - topic on which the message is published
qosLevel - quality of service level
isDup - if the message is a duplicate
isRetain - if the message needs to be retained
Return
a reference to this, so the API can be used fluently