public class MqttAsyncClient extends java.lang.Object implements IMqttAsyncClient
This class implements the non-blocking IMqttAsyncClient
client interface allowing applications to initiate
MQTT actions and then carry on working while the MQTT action completes on a background thread. This implementation is
compatible with all Java SE runtimes from 1.4.2 and up.
An application can connect to an MQTT server using:
To enable messages to be delivered even across network and client restarts messages need to be safely stored until the message has been delivered at the requested quality of service. A pluggable persistence mechanism is provided to store the messages.
If connecting with MqttConnectOptions.setCleanSession(boolean)
set to true it is safe to use memory
persistence as all state is cleared when a client disconnects. If connecting with cleanSession set to false in order
to provide reliable message delivery then a persistent message store such as the default one should be used.
The message store interface is pluggable. Different stores can be used by implementing the
MqttClientPersistence
interface and passing it to the clients constructor.
IMqttAsyncClient
Modifier and Type | Field and Description |
---|---|
protected ClientComms |
comms |
Constructor and Description |
---|
MqttAsyncClient(java.lang.String serverURI,
java.lang.String clientId)
Create an MqttAsyncClient that is used to communicate with an MQTT server.
|
MqttAsyncClient(java.lang.String serverURI,
java.lang.String clientId,
MqttClientPersistence persistence) |
MqttAsyncClient(java.lang.String serverURI,
java.lang.String clientId,
MqttClientPersistence persistence,
MqttPingSender pingSender)
Create an MqttAsyncClient that is used to communicate with an MQTT server.
|
Modifier and Type | Method and Description |
---|---|
IMqttToken |
checkPing(java.lang.Object userContext,
IMqttActionListener callback) |
void |
close()
Close the client Releases all resource associated with the client.
|
IMqttToken |
connect()
Connects to an MQTT server using the default options.
|
IMqttToken |
connect(MqttConnectOptions options)
Connects to an MQTT server using the provided connect options.
|
IMqttToken |
connect(MqttConnectOptions options,
java.lang.Object userContext,
IMqttActionListener callback)
Connects to an MQTT server using the specified options.
|
IMqttToken |
connect(java.lang.Object userContext,
IMqttActionListener callback)
Connects to an MQTT server using the default options.
|
protected NetworkModule[] |
createNetworkModules(java.lang.String address,
MqttConnectOptions options)
Factory method to create an array of network modules, one for each of the supplied URIs
|
IMqttToken |
disconnect()
Disconnects from the server.
|
IMqttToken |
disconnect(long quiesceTimeout)
Disconnects from the server.
|
IMqttToken |
disconnect(long quiesceTimeout,
java.lang.Object userContext,
IMqttActionListener callback)
Disconnects from the server.
|
IMqttToken |
disconnect(java.lang.Object userContext,
IMqttActionListener callback)
Disconnects from the server.
|
void |
disconnectForcibly()
Disconnects from the server forcibly to reset all the states.
|
void |
disconnectForcibly(long disconnectTimeout)
Disconnects from the server forcibly to reset all the states.
|
void |
disconnectForcibly(long quiesceTimeout,
long disconnectTimeout)
Disconnects from the server forcibly to reset all the states.
|
static java.lang.String |
generateClientId()
Returns a randomly generated client identifier based on the the fixed prefix (paho) and the system time.
|
java.lang.String |
getClientId()
Returns the client ID used by this client.
|
Debug |
getDebug()
Return a debug object that can be used to help solve problems.
|
IMqttDeliveryToken[] |
getPendingDeliveryTokens()
Returns the delivery tokens for any outstanding publish operations.
|
java.lang.String |
getServerURI()
Returns the address of the server used by this client.
|
protected MqttTopic |
getTopic(java.lang.String topic)
Get a topic object which can be used to publish messages.
|
boolean |
isConnected()
Determines if this client is currently connected to the server.
|
IMqttDeliveryToken |
publish(java.lang.String topic,
byte[] payload,
int qos,
boolean retained)
Publishes a message to a topic on the server.
|
IMqttDeliveryToken |
publish(java.lang.String topic,
byte[] payload,
int qos,
boolean retained,
java.lang.Object userContext,
IMqttActionListener callback)
Publishes a message to a topic on the server.
|
IMqttDeliveryToken |
publish(java.lang.String topic,
MqttMessage message)
Publishes a message to a topic on the server.
|
IMqttDeliveryToken |
publish(java.lang.String topic,
MqttMessage message,
java.lang.Object userContext,
IMqttActionListener callback)
Publishes a message to a topic on the server.
|
void |
setCallback(MqttCallback callback)
Sets a callback listener to use for events that happen asynchronously.
|
IMqttToken |
subscribe(java.lang.String[] topicFilters,
int[] qos)
Subscribe to multiple topics, each of which may include wildcards.
|
IMqttToken |
subscribe(java.lang.String[] topicFilters,
int[] qos,
java.lang.Object userContext,
IMqttActionListener callback)
Subscribes to multiple topics, each of which may include wildcards.
|
IMqttToken |
subscribe(java.lang.String topicFilter,
int qos)
Subscribe to a topic, which may include wildcards.
|
IMqttToken |
subscribe(java.lang.String topicFilter,
int qos,
java.lang.Object userContext,
IMqttActionListener callback)
Subscribe to a topic, which may include wildcards.
|
IMqttToken |
unsubscribe(java.lang.String topicFilter)
Requests the server unsubscribe the client from a topic.
|
IMqttToken |
unsubscribe(java.lang.String[] topicFilters)
Requests the server unsubscribe the client from one or more topics.
|
IMqttToken |
unsubscribe(java.lang.String[] topicFilters,
java.lang.Object userContext,
IMqttActionListener callback)
Requests the server unsubscribe the client from one or more topics.
|
IMqttToken |
unsubscribe(java.lang.String topicFilter,
java.lang.Object userContext,
IMqttActionListener callback)
Requests the server unsubscribe the client from a topics.
|
protected ClientComms comms
public MqttAsyncClient(java.lang.String serverURI, java.lang.String clientId) throws MqttException
The address of a server can be specified on the constructor. Alternatively a list containing one or more servers
can be specified using the setServerURIs
method on
MqttConnectOptions.
The serverURI
parameter is typically used with the the clientId
parameter to form a
key. The key is used to store and reference messages while they are being delivered. Hence the serverURI
specified on the constructor must still be specified even if a list of servers is specified on an
MqttConnectOptions object. The serverURI on the constructor must remain the same across restarts of the client
for delivery of messages to be maintained from a given client to a given server or set of servers.
The address of the server to connect to is specified as a URI. Two types of connection are supported
tcp://
for a TCP connection and ssl://
for a TCP connection secured by SSL/TLS. For
example:
tcp://localhost:1883
ssl://localhost:8883
tcp://
" URIs, and 8883 for
ssl://
URIs.
A client identifier clientId
must be specified and be less that 65535 characters. It must be unique
across all clients connecting to the same server. The clientId is used by the server to store data related to the
client, hence it is important that the clientId remain the same when connecting to a server if durable
subscriptions or reliable messaging are required.
A convenience method is provided to generate a random client id that should satisfy this criteria -
generateClientId()
. As the client identifier is used by the server to identify a client when it
reconnects, the client must use the same identifier between connections if durable subscriptions or reliable
delivery of messages is required.
In Java SE, SSL can be configured in one of several ways, which the client will use in the following order:
SSLSocketFactory
- applications can use
MqttConnectOptions.setSocketFactory(SocketFactory)
to supply a factory with the appropriate SSL settings.
MqttConnectOptions.setSSLProperties(Properties)
.In Java ME, the platform settings are used for SSL connections.
serverURI
- the address of the server to connect to, specified as a URI. Can be overridden using
MqttConnectOptions.setServerURIs(String[])
clientId
- a client identifier that is unique on the server being connected tojava.lang.IllegalArgumentException
- if the URI does not start with "tcp://", "ssl://" or "local://".java.lang.IllegalArgumentException
- if the clientId is null or is greater than 65535 characters in lengthMqttException
- if any other problem was encounteredpublic MqttAsyncClient(java.lang.String serverURI, java.lang.String clientId, @Nullable MqttClientPersistence persistence) throws MqttException
MqttException
public MqttAsyncClient(java.lang.String serverURI, java.lang.String clientId, @Nullable MqttClientPersistence persistence, MqttPingSender pingSender) throws MqttException
The address of a server can be specified on the constructor. Alternatively a list containing one or more servers
can be specified using the setServerURIs
method on
MqttConnectOptions.
The serverURI
parameter is typically used with the the clientId
parameter to form a
key. The key is used to store and reference messages while they are being delivered. Hence the serverURI
specified on the constructor must still be specified even if a list of servers is specified on an
MqttConnectOptions object. The serverURI on the constructor must remain the same across restarts of the client
for delivery of messages to be maintained from a given client to a given server or set of servers.
The address of the server to connect to is specified as a URI. Two types of connection are supported
tcp://
for a TCP connection and ssl://
for a TCP connection secured by SSL/TLS. For
example:
tcp://localhost:1883
ssl://localhost:8883
tcp://
" URIs, and 8883 for
ssl://
URIs.
A client identifier clientId
must be specified and be less that 65535 characters. It must be unique
across all clients connecting to the same server. The clientId is used by the server to store data related to the
client, hence it is important that the clientId remain the same when connecting to a server if durable
subscriptions or reliable messaging are required.
A convenience method is provided to generate a random client id that should satisfy this criteria -
generateClientId()
. As the client identifier is used by the server to identify a client when it
reconnects, the client must use the same identifier between connections if durable subscriptions or reliable
delivery of messages is required.
In Java SE, SSL can be configured in one of several ways, which the client will use in the following order:
SSLSocketFactory
- applications can use
MqttConnectOptions.setSocketFactory(SocketFactory)
to supply a factory with the appropriate SSL settings.
MqttConnectOptions.setSSLProperties(Properties)
.In Java ME, the platform settings are used for SSL connections.
A persistence mechanism is used to enable reliable messaging. For messages sent at qualities of service (QoS) 1
or 2 to be reliably delivered, messages must be stored (on both the client and server) until the delivery of the
message is complete. If messages are not safely stored when being delivered then a failure in the client or
server can result in lost messages. A pluggable persistence mechanism is supported via the
MqttClientPersistence
interface. An implementer of this interface that safely stores messages must be
specified in order for delivery of messages to be reliable. In addition
MqttConnectOptions.setCleanSession(boolean)
must be set to false. In the event that only QoS 0 messages
are sent or received or cleanSession is set to true then a safe store is not needed.
serverURI
- the address of the server to connect to, specified as a URI. Can be overridden using
MqttConnectOptions.setServerURIs(String[])
clientId
- a client identifier that is unique on the server being connected topersistence
- the persistence class to use to store in-flight message. If null then the default persistence
mechanism is usedjava.lang.IllegalArgumentException
- if the URI does not start with "tcp://", "ssl://" or "local://"java.lang.IllegalArgumentException
- if the clientId is null or is greater than 65535 characters in lengthMqttException
- if any other problem was encounteredprotected NetworkModule[] createNetworkModules(java.lang.String address, MqttConnectOptions options) throws MqttException, MqttSecurityException
address
- the URI for the server.MqttException
MqttSecurityException
public IMqttToken connect(@Nullable java.lang.Object userContext, @Nullable IMqttActionListener callback) throws MqttException, MqttSecurityException
IMqttAsyncClient
The default options are specified in MqttConnectOptions
class.
connect
in interface IMqttAsyncClient
userContext
- optional object used to pass context to the callback. Use null if not required.callback
- optional listener that will be notified when the connect completes. Use null if not required.MqttSecurityException
- for security related problemsMqttException
- for non security related problemsIMqttAsyncClient.connect(MqttConnectOptions, Object, IMqttActionListener)
public IMqttToken connect() throws MqttException, MqttSecurityException
IMqttAsyncClient
The default options are specified in MqttConnectOptions
class.
connect
in interface IMqttAsyncClient
MqttSecurityException
- for security related problemsMqttException
- for non security related problemsIMqttAsyncClient.connect(MqttConnectOptions, Object, IMqttActionListener)
public IMqttToken connect(MqttConnectOptions options) throws MqttException, MqttSecurityException
IMqttAsyncClient
The connection will be established using the options specified in the MqttConnectOptions
parameter.
connect
in interface IMqttAsyncClient
options
- a set of connection parameters that override the defaults.MqttSecurityException
- for security related problemsMqttException
- for non security related problemsIMqttAsyncClient.connect(MqttConnectOptions, Object, IMqttActionListener)
public IMqttToken connect(MqttConnectOptions options, @Nullable java.lang.Object userContext, @Nullable IMqttActionListener callback) throws MqttException, MqttSecurityException
IMqttAsyncClient
The server to connect to is specified on the constructor. It is recommended to call
IMqttAsyncClient.setCallback(MqttCallback)
prior to connecting in order that messages destined for the client can be
accepted as soon as the client is connected.
The method returns control before the connect completes. Completion can be tracked by:
IMqttToken.waitForCompletion()
orIMqttActionListener
connect
in interface IMqttAsyncClient
options
- a set of connection parameters that override the defaults.userContext
- optional object for used to pass context to the callback. Use null if not required.callback
- optional listener that will be notified when the connect completes. Use null if not required.MqttSecurityException
- for security related problemsMqttException
- for non security related problems including communication errorspublic IMqttToken disconnect(@Nullable java.lang.Object userContext, @Nullable IMqttActionListener callback) throws MqttException
IMqttAsyncClient
An attempt is made to quiesce the client allowing outstanding work to complete before disconnecting. It will wait
for a maximum of 30 seconds for work to quiesce before disconnecting. This method must not be called from inside
MqttCallback
methods.
disconnect
in interface IMqttAsyncClient
userContext
- optional object used to pass context to the callback. Use null if not required.callback
- optional listener that will be notified when the disconnect completes. Use null if not required.MqttException
- for problems encountered while disconnectingIMqttAsyncClient.disconnect(long, Object, IMqttActionListener)
public IMqttToken disconnect() throws MqttException
IMqttAsyncClient
An attempt is made to quiesce the client allowing outstanding work to complete before disconnecting. It will wait
for a maximum of 30 seconds for work to quiesce before disconnecting. This method must not be called from inside
MqttCallback
methods.
disconnect
in interface IMqttAsyncClient
MqttException
- for problems encountered while disconnectingIMqttAsyncClient.disconnect(long, Object, IMqttActionListener)
public IMqttToken disconnect(long quiesceTimeout) throws MqttException
IMqttAsyncClient
An attempt is made to quiesce the client allowing outstanding work to complete before disconnecting. It will wait
for a maximum of the specified quiesce time for work to complete before disconnecting. This method must not be
called from inside MqttCallback
methods.
disconnect
in interface IMqttAsyncClient
quiesceTimeout
- the amount of time in milliseconds to allow for existing work to finish before disconnecting. A value
of zero or less means the client will not quiesce.MqttException
- for problems encountered while disconnectingIMqttAsyncClient.disconnect(long, Object, IMqttActionListener)
public IMqttToken disconnect(long quiesceTimeout, @Nullable java.lang.Object userContext, @Nullable IMqttActionListener callback) throws MqttException
IMqttAsyncClient
The client will wait for MqttCallback
methods to complete. It will then wait for up to the quiesce
timeout to allow for work which has already been initiated to complete. For instance when a QoS 2 message has
started flowing to the server but the QoS 2 flow has not completed.It prevents new messages being accepted and
does not send any messages that have been accepted but not yet started delivery across the network to the server.
When work has completed or after the quiesce timeout, the client will disconnect from the server. If the
cleanSession flag was set to false and is set to false the next time a connection is made QoS 1 and 2 messages
that were not previously delivered will be delivered.
This method must not be called from inside MqttCallback
methods.
The method returns control before the disconnect completes. Completion can be tracked by:
IMqttToken.waitForCompletion()
orIMqttActionListener
disconnect
in interface IMqttAsyncClient
quiesceTimeout
- the amount of time in milliseconds to allow for existing work to finish before disconnecting. A value
of zero or less means the client will not quiesce.userContext
- optional object used to pass context to the callback. Use null if not required.callback
- optional listener that will be notified when the disconnect completes. Use null if not required.MqttException
- for problems encountered while disconnectingpublic void disconnectForcibly() throws MqttException
IMqttAsyncClient
Because the client is able to establish the TCP/IP connection to a none MQTT server and it will certainly fail to send the disconnect packet. It will wait for a maximum of 30 seconds for work to quiesce before disconnecting and wait for a maximum of 10 seconds for sending the disconnect packet to server.
disconnectForcibly
in interface IMqttAsyncClient
MqttException
- if any unexpected errorpublic void disconnectForcibly(long disconnectTimeout) throws MqttException
IMqttAsyncClient
Because the client is able to establish the TCP/IP connection to a none MQTT server and it will certainly fail to send the disconnect packet. It will wait for a maximum of 30 seconds for work to quiesce before disconnecting.
disconnectForcibly
in interface IMqttAsyncClient
disconnectTimeout
- the amount of time in milliseconds to allow send disconnect packet to server.MqttException
- if any unexpected errorpublic void disconnectForcibly(long quiesceTimeout, long disconnectTimeout) throws MqttException
IMqttAsyncClient
Because the client is able to establish the TCP/IP connection to a none MQTT server and it will certainly fail to send the disconnect packet.
disconnectForcibly
in interface IMqttAsyncClient
quiesceTimeout
- the amount of time in milliseconds to allow for existing work to finish before disconnecting. A value
of zero or less means the client will not quiesce.disconnectTimeout
- the amount of time in milliseconds to allow send disconnect packet to server.MqttException
- if any unexpected errorpublic boolean isConnected()
IMqttAsyncClient
isConnected
in interface IMqttAsyncClient
true
if connected, false
otherwise.public java.lang.String getClientId()
IMqttAsyncClient
All clients connected to the same server or server farm must have a unique ID.
getClientId
in interface IMqttAsyncClient
public java.lang.String getServerURI()
IMqttAsyncClient
The format of the returned String is the same as that used on the constructor.
getServerURI
in interface IMqttAsyncClient
MqttAsyncClient(String, String)
protected MqttTopic getTopic(java.lang.String topic)
There are two alternative methods that should be used in preference to this one when publishing a message:
publish(java.lang.String, byte[], int, boolean)
to publish a message in a
non-blocking manner or
MqttClient.publish(java.lang.String, org.eclipse.paho.client.mqttv3.MqttMessage)
to publish a message
in a blocking manner
When you build an application, the design of the topic tree should take into account the following principles of topic name syntax and semantics:
The following principles apply to the construction and content of a topic tree:
topic
- the topic to use, for example "finance/stock/ibm".java.lang.IllegalArgumentException
- if the topic contains a '+' or '#' wildcard character.public IMqttToken checkPing(java.lang.Object userContext, IMqttActionListener callback) throws MqttException
MqttException
public IMqttToken subscribe(java.lang.String topicFilter, int qos, @Nullable java.lang.Object userContext, IMqttActionListener callback) throws MqttException
IMqttAsyncClient
subscribe
in interface IMqttAsyncClient
topicFilter
- the topic to subscribe to, which can include wildcards.qos
- the maximum quality of service at which to subscribe. Messages published at a lower quality of service
will be received at the published QoS. Messages published at a higher quality of service will be
received using the QoS specified on the subscribe.userContext
- optional object used to pass context to the callback. Use null if not required.callback
- optional listener that will be notified when subscribe has completedMqttException
- if there was an error registering the subscription.IMqttAsyncClient.subscribe(String[], int[], Object, IMqttActionListener)
public IMqttToken subscribe(java.lang.String topicFilter, int qos) throws MqttException
IMqttAsyncClient
subscribe
in interface IMqttAsyncClient
topicFilter
- the topic to subscribe to, which can include wildcards.qos
- the maximum quality of service at which to subscribe. Messages published at a lower quality of service
will be received at the published QoS. Messages published at a higher quality of service will be
received using the QoS specified on the subscribe.MqttException
- if there was an error registering the subscription.IMqttAsyncClient.subscribe(String[], int[], Object, IMqttActionListener)
public IMqttToken subscribe(java.lang.String[] topicFilters, int[] qos) throws MqttException
IMqttAsyncClient
Provides an optimized way to subscribe to multiple topics compared to subscribing to each one individually.
subscribe
in interface IMqttAsyncClient
topicFilters
- one or more topics to subscribe to, which can include wildcardsqos
- the maximum quality of service at which to subscribe. Messages published at a lower quality of service
will be received at the published QoS. Messages published at a higher quality of service will be
received using the QoS specified on the subscribe.MqttException
- if there was an error registering the subscription.IMqttAsyncClient.subscribe(String[], int[], Object, IMqttActionListener)
public IMqttToken subscribe(java.lang.String[] topicFilters, int[] qos, @Nullable java.lang.Object userContext, @Nullable IMqttActionListener callback) throws MqttException
IMqttAsyncClient
Provides an optimized way to subscribe to multiple topics compared to subscribing to each one individually.
The IMqttAsyncClient.setCallback(MqttCallback)
method should be called before this method, otherwise any received
messages will be discarded.
If (@link MqttConnectOptions#setCleanSession(boolean)} was set to true when when connecting to the server then the subscription remains in place until either:
The "topic filter" string used when subscribing may contain special characters, which allow you to subscribe to multiple topics at once.
The topic level separator is used to introduce structure into the topic, and can therefore be specified within the topic for that purpose. The multi-level wildcard and single-level wildcard can be used for subscriptions, but they cannot be used within a topic by the publisher of a message.
The number sign (#) is a wildcard character that matches any number of levels within a topic. For example, if you
subscribe to finance/stock/ibm/#, you receive messages on these
topics:
finance / stock / ibm
finance / stock / ibm / closingprice
finance / stock / ibm / currentprice
The multi-level wildcard can represent zero or more levels. Therefore, finance/# can also match the singular finance, where # represents zero levels. The topic level separator is meaningless in this context, because there are no levels to separate.
The multi-level wildcard can be specified only on its own or next to the topic level separator character. Therefore, # and finance/# are both valid, but finance# is not valid. The multi-level wildcard must be the last character used within the topic tree. For example, finance/# is valid but finance/#/closingprice is not valid.
The plus sign (+) is a wildcard character that matches only one topic level. For example, finance/stock/+ matches finance/stock/ibm and finance/stock/xyz, but not finance/stock/ibm/closingprice. Also, because the single-level wildcard matches only a single level, finance/+ does not match finance.
Use the single-level wildcard at any level in the topic tree, and in conjunction with the multilevel wildcard. Specify the single-level wildcard next to the topic level separator, except when it is specified on its own. Therefore, + and finance/+ are both valid, but finance+ is not valid. The single-level wildcard can be used at the end of the topic tree or within the topic tree. For example, finance/+ and finance/+/ibm are both valid.
The method returns control before the subscribe completes. Completion can be tracked by:
MqttToken.waitForCompletion()
orIMqttActionListener
to this methodsubscribe
in interface IMqttAsyncClient
topicFilters
- one or more topics to subscribe to, which can include wildcardsqos
- the maximum quality of service to subscribe each topic at.Messages published at a lower quality of
service will be received at the published QoS. Messages published at a higher quality of service will
be received using the QoS specified on the subscribe.userContext
- optional object used to pass context to the callback. Use null if not required.callback
- optional listener that will be notified when subscribe has completedMqttException
- if there was an error registering the subscription.public IMqttToken unsubscribe(java.lang.String topicFilter, @Nullable java.lang.Object userContext, IMqttActionListener callback) throws MqttException
IMqttAsyncClient
unsubscribe
in interface IMqttAsyncClient
topicFilter
- the topic to unsubscribe from. It must match a topicFilter specified on an earlier subscribe.userContext
- optional object used to pass context to the callback. Use null if not required.callback
- optional listener that will be notified when unsubscribe has completedMqttException
- if there was an error unregistering the subscription.IMqttAsyncClient.unsubscribe(String[], Object, IMqttActionListener)
public IMqttToken unsubscribe(java.lang.String topicFilter) throws MqttException
IMqttAsyncClient
unsubscribe
in interface IMqttAsyncClient
topicFilter
- the topic to unsubscribe from. It must match a topicFilter specified on an earlier subscribe.MqttException
- if there was an error unregistering the subscription.IMqttAsyncClient.unsubscribe(String[], Object, IMqttActionListener)
public IMqttToken unsubscribe(java.lang.String[] topicFilters) throws MqttException
IMqttAsyncClient
unsubscribe
in interface IMqttAsyncClient
topicFilters
- one or more topics to unsubscribe from. Each topicFilter must match one specified on an earlier
subscribe. *MqttException
- if there was an error unregistering the subscription.IMqttAsyncClient.unsubscribe(String[], Object, IMqttActionListener)
public IMqttToken unsubscribe(java.lang.String[] topicFilters, @Nullable java.lang.Object userContext, @Nullable IMqttActionListener callback) throws MqttException
IMqttAsyncClient
Unsubcribing is the opposite of subscribing. When the server receives the unsubscribe request it looks to see if it can find a matching subscription for the client and then removes it. After this point the server will send no more messages to the client for this subscription.
The topic(s) specified on the unsubscribe must match the topic(s) specified in the original subscribe request for the unsubscribe to succeed
The method returns control before the unsubscribe completes. Completion can be tracked by:
MqttToken.waitForCompletion()
orIMqttActionListener
to this methodunsubscribe
in interface IMqttAsyncClient
topicFilters
- one or more topics to unsubscribe from. Each topicFilter must match one specified on an earlier
subscribe.userContext
- optional object used to pass context to the callback. Use null if not required.callback
- optional listener that will be notified when unsubscribe has completedMqttException
- if there was an error unregistering the subscription.public void setCallback(MqttCallback callback)
IMqttAsyncClient
There are a number of events that the listener will be notified about. These include:
Other events that track the progress of an individual operation such as connect and subscribe can be tracked
using the MqttToken
returned from each non-blocking method or using setting a IMqttActionListener
on the non-blocking method.
setCallback
in interface IMqttAsyncClient
callback
- which will be invoked for certain asynchronous eventsMqttCallback
public static java.lang.String generateClientId()
When cleanSession is set to false, an application must ensure it uses the same client identifier when it reconnects to the server to resume state and maintain assured message delivery.
MqttConnectOptions.setCleanSession(boolean)
public IMqttDeliveryToken[] getPendingDeliveryTokens()
IMqttAsyncClient
If a client has been restarted and there are messages that were in the process of being delivered when the client
stopped this method returns a token for each in-flight message enabling the delivery to be tracked Alternately
the MqttCallback.deliveryComplete(IMqttDeliveryToken)
callback can be used to track the delivery of
outstanding messages.
If a client connects with cleanSession true then there will be no delivery tokens as the cleanSession option deletes all earlier state. For state to be remembered the client must connect with cleanSession set to false
getPendingDeliveryTokens
in interface IMqttAsyncClient
public IMqttDeliveryToken publish(java.lang.String topic, byte[] payload, int qos, boolean retained, @Nullable java.lang.Object userContext, @Nullable IMqttActionListener callback) throws MqttException, MqttPersistenceException
IMqttAsyncClient
A convenience method, which will create a new MqttMessage
object with a byte array payload and the
specified QoS, and then publish it.
publish
in interface IMqttAsyncClient
topic
- to deliver the message to, for example "finance/stock/ibm".payload
- the byte array to use as the payloadqos
- the Quality of Service to deliver the message at. Valid values are 0, 1 or 2.retained
- whether or not this message should be retained by the server.userContext
- optional object used to pass context to the callback. Use null if not required.callback
- optional listener that will be notified when message delivery hsa completed to the requested quality
of serviceMqttPersistenceException
- when a problem occurs storing the messageMqttException
- for other errors encountered while publishing the message. For instance client not connected.IMqttAsyncClient.publish(String, MqttMessage, Object, IMqttActionListener)
,
MqttMessage.setQos(int)
,
MqttMessage.setRetained(boolean)
public IMqttDeliveryToken publish(java.lang.String topic, byte[] payload, int qos, boolean retained) throws MqttException, MqttPersistenceException
IMqttAsyncClient
A convenience method, which will create a new MqttMessage
object with a byte array payload and the
specified QoS, and then publish it.
publish
in interface IMqttAsyncClient
topic
- to deliver the message to, for example "finance/stock/ibm".payload
- the byte array to use as the payloadqos
- the Quality of Service to deliver the message at. Valid values are 0, 1 or 2.retained
- whether or not this message should be retained by the server.MqttPersistenceException
- when a problem occurs storing the messageMqttException
- for other errors encountered while publishing the message. For instance if too many messages are
being processed.IMqttAsyncClient.publish(String, MqttMessage, Object, IMqttActionListener)
,
MqttMessage.setQos(int)
,
MqttMessage.setRetained(boolean)
public IMqttDeliveryToken publish(java.lang.String topic, MqttMessage message) throws MqttException, MqttPersistenceException
IMqttAsyncClient
MqttMessage
message and delivers it to the server
at the requested quality of service.publish
in interface IMqttAsyncClient
topic
- to deliver the message to, for example "finance/stock/ibm".message
- to deliver to the serverMqttPersistenceException
- when a problem occurs storing the messageMqttException
- for other errors encountered while publishing the message. For instance client not connected.IMqttAsyncClient.publish(String, MqttMessage, Object, IMqttActionListener)
public IMqttDeliveryToken publish(java.lang.String topic, MqttMessage message, @Nullable java.lang.Object userContext, @Nullable IMqttActionListener callback) throws MqttException, MqttPersistenceException
IMqttAsyncClient
Once this method has returned cleanly, the message has been accepted for publication by the client and will be delivered on a background thread. In the event the connection fails or the client stops. Messages will be delivered to the requested quality of service once the connection is re-established to the server on condition that:
When building an application, the design of the topic tree should take into account the following principles of topic name syntax and semantics:
The following principles apply to the construction and content of a topic tree:
The method returns control before the publish completes. Completion can be tracked by:
IMqttAsyncClient.setCallback(MqttCallback)
where the
MqttCallback.deliveryComplete(IMqttDeliveryToken)
method will be called.MqttToken.waitForCompletion()
orIMqttActionListener
to this methodpublish
in interface IMqttAsyncClient
topic
- to deliver the message to, for example "finance/stock/ibm".message
- to deliver to the serveruserContext
- optional object used to pass context to the callback. Use null if not required.callback
- optional listener that will be notified when message delivery has completed to the requested quality
of serviceMqttPersistenceException
- when a problem occurs storing the messageMqttException
- for other errors encountered while publishing the message. For instance client not connected.MqttMessage
public void close() throws MqttException
IMqttAsyncClient
close
in interface IMqttAsyncClient
MqttException
- if the client is not disconnected.public Debug getDebug()