com.microsoft.azure.sdk.iot.device.transport.mqtt

Class MqttTransport

java.lang.Object

com.microsoft.azure.sdk.iot.device.transport.mqtt.MqttTransport

All Implemented Interfaces:

IotHubTransport, Closeable, AutoCloseable

public final class MqttTransport
extends Object
implements IotHubTransport

An MQTT transport. Contains functionality for adding messages and sending batched messages to an IoT Hub. Buffers unsent messages until they are received by an IoT Hub. A transport is bound at construction to the following parameters: IoT Hub name, device ID, device key, and message valid seconds.

The transport can also poll an IoT Hub for messages and invoke a user-defined message callback if a message and callback is found.

Field Summary

Fields

Modifier and Type	Field and Description
protected Queue<IotHubCallbackPacket>	callbackList Messages whose callbacks that are waiting to be invoked.
protected DeviceClientConfig	config
protected Object	handleMessageLock
protected MqttIotHubConnection	mqttIotHubConnection The MQTT connection.
protected Object	sendMessagesLock The MQTT connection lock.
protected State	state
protected Queue<IotHubOutboundPacket>	waitingList Messages waiting to be sent.

Constructor Summary

Constructors

Constructor and Description
MqttTransport(DeviceClientConfig config) Constructs an instance from the given DeviceClientConfig object.

Method Summary

Modifier and Type	Method and Description
void	addMessage(Message message, IotHubEventCallback callback, Object callbackContext) Adds a message to the transport queue.
void	close() Closes all resources used to communicate with an IoT Hub.
void	handleMessage() Invokes the message callback every time a message arrives from the server.
void	invokeCallbacks() Invokes the callbacks for all completed requests.
boolean	isEmpty() Returns true if the transport has no more messages to handle, and false otherwise.
void	open() Establishes a communication channel with an IoT Hub.
void	sendMessages() Sends all messages on the transport queue, one at a time.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

sendMessagesLock

protected final Object sendMessagesLock

The MQTT connection lock.

handleMessageLock

protected final Object handleMessageLock

state

protected State state

mqttIotHubConnection

protected MqttIotHubConnection mqttIotHubConnection

The MQTT connection.

waitingList

protected final Queue<IotHubOutboundPacket> waitingList

Messages waiting to be sent.

callbackList

protected final Queue<IotHubCallbackPacket> callbackList

Messages whose callbacks that are waiting to be invoked.

config

protected final DeviceClientConfig config

Constructor Detail

MqttTransport

public MqttTransport(DeviceClientConfig config)

Constructs an instance from the given DeviceClientConfig object.

Parameters:

config - configuration parameters for the connection.

Method Detail

open

public void open()
          throws IOException

Establishes a communication channel with an IoT Hub. If a channel is already open, the function shall do nothing.

Specified by:

open in interface IotHubTransport

Throws:

IOException - if a communication channel cannot be established.

close

public void close()

Closes all resources used to communicate with an IoT Hub. Once close() is called, the transport is no longer usable. If the transport is already closed, the function shall do nothing.

Specified by:

close in interface IotHubTransport

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

addMessage

public void addMessage(Message message,
                       IotHubEventCallback callback,
                       Object callbackContext)
                throws IllegalStateException

Adds a message to the transport queue.

Specified by:

addMessage in interface IotHubTransport

Parameters:

message - the message to be sent.

callback - the callback to be invoked when a response for the message is received.

callbackContext - the context to be passed in when the callback is invoked.

Throws:

IllegalStateException - if the transport has not been opened or is closed

sendMessages

public void sendMessages()
                  throws IllegalStateException

Sends all messages on the transport queue, one at a time. If a previous send attempt had failed, the function will attempt to resend the messages in the previous attempt.

If one has not already been created, the function will initialize an MQTT connection with the IoT Hub specified in the configuration.

Specified by:

sendMessages in interface IotHubTransport

Throws:

IllegalStateException - if the transport has not been opened or is closed.

invokeCallbacks

public void invokeCallbacks()
                     throws IllegalStateException

Invokes the callbacks for all completed requests.

Specified by:

invokeCallbacks in interface IotHubTransport

Throws:

IllegalStateException - if the transport has not been opened or is closed.

handleMessage

public void handleMessage()
                   throws IllegalStateException

Invokes the message callback every time a message arrives from the server. responds to the IoT Hub on how the processed message should be handled by the IoT Hub.

If no message callback is set, the function will do nothing.

Specified by:

handleMessage in interface IotHubTransport

Throws:

IllegalStateException - if the transport has not been opened or is closed.

isEmpty

public boolean isEmpty()

Returns true if the transport has no more messages to handle, and false otherwise.

Specified by:

isEmpty in interface IotHubTransport

Returns:

true if the transport has no more messages to handle, and false otherwise.