org.eclipse.paho.mqttv5.client.IMqttClient Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2009, 2019 IBM Corp.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v2.0
* and Eclipse Distribution License v1.0 which accompany this distribution.
*
* The Eclipse Public License is available at
* https://www.eclipse.org/legal/epl-2.0
* and the Eclipse Distribution License is available at
* https://www.eclipse.org/org/documents/edl-v10.php
*
* Contributors:
* James Sutton - MQTT V5 support
*/
package org.eclipse.paho.mqttv5.client;
import org.eclipse.paho.mqttv5.common.MqttException;
import org.eclipse.paho.mqttv5.common.MqttMessage;
import org.eclipse.paho.mqttv5.common.MqttPersistenceException;
import org.eclipse.paho.mqttv5.common.MqttSecurityException;
import org.eclipse.paho.mqttv5.common.MqttSubscription;
/**
* Enables an application to communicate with an MQTT server using blocking methods.
*
* This interface allows applications to utilize all features of the MQTT version 3.1
* specification including:
*
* - connect
*
- publish
*
- subscribe
*
- unsubscribe
*
- disconnect
*
*
* There are two styles of MQTT client, this one and {@link IMqttAsyncClient}.
*
* - IMqttClient provides a set of methods that block and return control to the application
* program once the MQTT action has completed.
* - IMqttAsyncClient provides a set of non-blocking methods that return control to the
* invoking application after initial validation of parameters and state. The main processing is
* performed in the background so as not to block the application programs thread. This non
* blocking approach is handy when the application wants to carry on processing while the
* MQTT action takes place. For instance connecting to an MQTT server can take time, using
* the non-blocking connect method allows an application to display a busy indicator while the
* connect action is occurring. Non-blocking methods are particularly useful in event-oriented
* programs and graphical programs where issuing methods that take time to complete on the the
* main or GUI thread can cause problems.
*
*
* The non-blocking client can also be used in a blocking form by turning a non-blocking
* method into a blocking invocation using the following pattern:
*
* IMqttToken token;
* token = asyncClient.method(parms).waitForCompletion();
*
*
* Using the non-blocking client allows an application to use a mixture of blocking and
* non-blocking styles. Using the blocking client only allows an application to use one
* style. The blocking client provides compatibility with earlier versions
* of the MQTT client.
*/
public interface IMqttClient { //extends IMqttAsyncClient {
/**
* Connects to an MQTT server using the default options.
* The default options are specified in {@link MqttConnectionOptions} class.
*
*
* @throws MqttSecurityException when the server rejects the connect for security
* reasons
* @throws MqttException for non security related problems
* @see #connect(MqttConnectionOptions)
*/
public void connect() throws MqttSecurityException, MqttException;
/**
* Connects to an MQTT server using the specified options.
* The server to connect to is specified on the constructor.
* It is recommended to call {@link #setCallback(MqttCallback)} prior to
* connecting in order that messages destined for the client can be accepted
* as soon as the client is connected.
*
* This is a blocking method that returns once connect completes
*
* @param options a set of connection parameters that override the defaults.
* @throws MqttSecurityException when the server rejects the connect for security
* reasons
* @throws MqttException for non security related problems including communication errors
*/
public void connect(MqttConnectionOptions options) throws MqttSecurityException, MqttException;
/**
* Connects to an MQTT server using the specified options.
* The server to connect to is specified on the constructor.
* It is recommended to call {@link #setCallback(MqttCallback)} prior to
* connecting in order that messages destined for the client can be accepted
* as soon as the client is connected.
*
* This is a blocking method that returns once connect completes
*
* @param options a set of connection parameters that override the defaults.
* @return the MqttToken used for the call. Can be used to obtain the session present flag
* @throws MqttSecurityException when the server rejects the connect for security
* reasons
* @throws MqttException for non security related problems including communication errors
*/
public IMqttToken connectWithResult(MqttConnectionOptions options) throws MqttSecurityException, MqttException;
/**
* Disconnects from the server.
* 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 {@link MqttCallback} methods.
*
*
* This is a blocking method that returns once disconnect completes
*
* @throws MqttException if a problem is encountered while disconnecting
*/
public void disconnect() throws MqttException;
/**
* Disconnects from the server.
*
* The client will wait for all {@link 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 example, it will
* wait for the QoS 2 flows from earlier publications to complete. When work has
* completed or after the quiesce timeout, the client will disconnect from
* the server. If the cleanStart 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 is a blocking method that returns once disconnect completes
*
* @param 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.
* @throws MqttException if a problem is encountered while disconnecting
*/
public void disconnect(long quiesceTimeout) throws MqttException;
/**
* Disconnects from the server forcibly to reset all the states. Could be useful when disconnect attempt failed.
*
* 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.
*
* @throws MqttException if any unexpected error
* @since 0.4.1
*/
public void disconnectForcibly() throws MqttException;
/**
* Disconnects from the server forcibly to reset all the states. Could be useful when disconnect attempt failed.
*
* 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.
*
* @param disconnectTimeout the amount of time in milliseconds to allow send disconnect packet to server.
* @throws MqttException if any unexpected error
* @since 0.4.1
*/
public void disconnectForcibly(long disconnectTimeout) throws MqttException;
/**
* Disconnects from the server forcibly to reset all the states. Could be useful when disconnect attempt failed.
*
* 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.
*
* @param 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.
* @param disconnectTimeout the amount of time in milliseconds to allow send disconnect packet to server.
* @throws MqttException if any unexpected error
* @since 0.4.1
*/
public void disconnectForcibly(long quiesceTimeout, long disconnectTimeout) throws MqttException;
/**
* Subscribe to a topic, which may include wildcards.
*
* @see #subscribe(String[], int[])
*
* @param topicFilter the topic to subscribe to, which can include wildcards.
* @param 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.
* @return a token
* @throws MqttException if there was an error registering the subscription.
*/
public IMqttToken subscribe(String topicFilter, int qos) throws MqttException;
/**
* Subscribes to multiple topics, each of which may include wildcards.
*
The {@link #setCallback(MqttCallback)} method
* should be called before this method, otherwise any received messages
* will be discarded.
*
*
* If (@link MqttConnectOptions#setCleanStart(boolean)} was set to true
* when when connecting to the server then the subscription remains in place
* until either:
*
*
* - The client disconnects
* - An unsubscribe method is called to un-subscribe the topic
*
*
* If (@link MqttConnectOptions#setCleanStart(boolean)} was set to false
* when when connecting to the server then the subscription remains in place
* until either:
*
* - An unsubscribe method is called to unsubscribe the topic
* - The client connects with cleanStart set to true
*
*
* With cleanStart set to false the MQTT server will store messages on
* behalf of the client when the client is not connected. The next time the
* client connects with the same client ID the server will
* deliver the stored messages to the client.
*
*
* 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.
*
* - Topic level separator
* - The forward slash (/) is used to separate each level within
* a topic tree and provide a hierarchical structure to the topic space. The
* use of the topic level separator is significant when the two wildcard characters
* are encountered in topics specified by subscribers.
*
* - Multi-level wildcard
* 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.
- Single-level wildcard
* 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.
*
*
* This is a blocking method that returns once subscribe completes
*
* @param topicFilters one or more topics to subscribe to, which can include wildcards.
* @param qos 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.
* @return a token
* @throws MqttException if there was an error registering the subscription.
* @throws IllegalArgumentException if the two supplied arrays are not the same size.
*/
public IMqttToken subscribe(String[] topicFilters, int[] qos) throws MqttException;
/**
* Subscribes to a one or more topics, which may include wildcards using a QoS of 1.
*
* @see #subscribe(String[], int[])
*
* @param topicFilter the topic to subscribe to, which can include wildcards.
* @param qos QoS
* @param messageListener one callbacks to handle incoming messages
* @return a token
* @throws MqttException if there was an error registering the subscription.
*/
public IMqttToken subscribe(String topicFilter, int qos, IMqttMessageListener messageListener) throws MqttException;
/**
* Subscribes to multiple topics, each of which may include wildcards.
* The {@link #setCallback(MqttCallback)} method
* should be called before this method, otherwise any received messages
* will be discarded.
*
*
* If (@link MqttConnectOptions#setCleanStart(boolean)} was set to true
* when when connecting to the server then the subscription remains in place
* until either:
*
* - The client disconnects
* - An unsubscribe method is called to un-subscribe the topic
*
*
* If (@link MqttConnectOptions#setCleanStart(boolean)} was set to false
* when when connecting to the server then the subscription remains in place
* until either:
*
* - An unsubscribe method is called to unsubscribe the topic
* - The client connects with cleanStart set to true
*
*
* With cleanStart set to false the MQTT server will store messages on
* behalf of the client when the client is not connected. The next time the
* client connects with the same client ID the server will
* deliver the stored messages to the client.
*
*
* 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.
*
* - Topic level separator
* - The forward slash (/) is used to separate each level within
* a topic tree and provide a hierarchical structure to the topic space. The
* use of the topic level separator is significant when the two wildcard characters
* are encountered in topics specified by subscribers.
*
* - Multi-level wildcard
* 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.
- Single-level wildcard
* 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.
*
*
* This is a blocking method that returns once subscribe completes
*
* @param topicFilters one or more topics to subscribe to, which can include wildcards.
* @param qos 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.
* @param messageListeners one or more callbacks to handle incoming messages
* @return a token
* @throws MqttException if there was an error registering the subscription.
* @throws IllegalArgumentException if the two supplied arrays are not the same size.
*/
public IMqttToken subscribe(String[] topicFilters, int[] qos, IMqttMessageListener[] messageListeners) throws MqttException;
/**
* Requests the server unsubscribe the client from a topic.
*
* @see #unsubscribe(String[])
* @param topicFilter the topic to unsubscribe from. It must match a topicFilter
* specified on the subscribe.
* @throws MqttException if there was an error unregistering the subscription.
*/
public void unsubscribe(String topicFilter) throws MqttException;
/**
* Requests the server unsubscribe the client from one or more topics.
*
* Unsubcribing is the opposite of subscribing. When the server receives the
* unsubscribe request it looks to see if it can find a 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 subscribe to succeed
*
*
* This is a blocking method that returns once unsubscribe completes
*
* @param topicFilters one or more topics to unsubscribe from. Each topicFilter
* must match one specified on a subscribe
* @throws MqttException if there was an error unregistering the subscription.
*/
public void unsubscribe(String[] topicFilters) throws MqttException;
/**
* Publishes a message to a topic on the server and return once it is delivered.
* This is a convenience method, which will
* create a new {@link MqttMessage} object with a byte array payload and the
* specified QoS, and then publish it. All other values in the
* message will be set to the defaults.
*
*
* @param topic to deliver the message to, for example "finance/stock/ibm".
* @param payload the byte array to use as the payload
* @param qos the Quality of Service to deliver the message at. Valid values are 0, 1 or 2.
* @param retained whether or not this message should be retained by the server.
* @throws MqttPersistenceException when a problem with storing the message
* @throws IllegalArgumentException if value of QoS is not 0, 1 or 2.
* @throws MqttException for other errors encountered while publishing the message.
* For instance client not connected.
* @see #publish(String, MqttMessage)
* @see MqttMessage#setQos(int)
* @see MqttMessage#setRetained(boolean)
*/
public void publish(String topic, byte[] payload, int qos, boolean retained) throws MqttException, MqttPersistenceException;
/**
* Publishes a message to a topic on the server.
*
* Delivers a message to the server at the requested quality of service and returns control
* once the message has been delivered. In the event the connection fails or the client
* stops, any messages that are in the process of being delivered will be delivered once
* a connection is re-established to the server on condition that:
*
* - The connection is re-established with the same clientID
* - The original connection was made with (@link MqttConnectOptions#setCleanStart(boolean)}
* set to false
* - The connection is re-established with (@link MqttConnectOptions#setCleanStart(boolean)}
* set to false
*
* In the event that the connection breaks or the client stops it is still possible to determine
* when the delivery of the message completes. Prior to re-establishing the connection to the server:
*
* - Register a {@link #setCallback(MqttCallback)} callback on the client and the delivery complete
* callback will be notified once a delivery of a message completes
*
- or call {@link #getPendingTokens()} which will return a token for each message that
* is in-flight. The token can be used to wait for delivery to complete.
*
*
* When building an application,
* the design of the topic tree should take into account the following principles
* of topic name syntax and semantics:
*
*
* - A topic must be at least one character long.
* - Topic names are case sensitive. For example, ACCOUNTS and Accounts are
* two different topics.
* - Topic names can include the space character. For example, Accounts
* payable is a valid topic.
* - A leading "/" creates a distinct topic. For example, /finance is
* different from finance. /finance matches "+/+" and "/+", but
* not "+".
* - Do not include the null character (Unicode
\x0000
) in
* any topic.
*
*
* The following principles apply to the construction and content of a topic
* tree:
*
*
* - The length is limited to 64k but within that there are no limits to the
* number of levels in a topic tree.
* - There can be any number of root nodes; that is, there can be any number
* of topic trees.
*
*
*
* This is a blocking method that returns once publish completes
*
*
* @param topic to deliver the message to, for example "finance/stock/ibm".
* @param message to delivery to the server
* @throws MqttPersistenceException when a problem with storing the message
* @throws MqttException for other errors encountered while publishing the message.
* For instance client not connected.
*/
public void publish(String topic, MqttMessage message) throws MqttException, MqttPersistenceException;
/**
* Sets the callback listener to use for events that happen asynchronously.
* There are a number of events that listener will be notified about. These include:
*
* - A new message has arrived and is ready to be processed
* - The connection to the server has been lost
* - Delivery of a message to the server has completed.
*
* Other events that track the progress of an individual operation such
* as connect and subscribe can be tracked using the {@link MqttToken} passed to the
* operation
* @see MqttCallback
* @param callback the class to callback when for events related to the client
*/
public void setCallback(MqttCallback callback);
/**
* Get a topic object which can be used to publish messages.
*
An alternative method that should be used in preference to this one when publishing a message is:
*
* - {@link MqttClient#publish(String, MqttMessage)} to publish a message in a blocking manner
*
- or use publish methods on the non-blocking client like {@link IMqttAsyncClient#publish(String, MqttMessage, Object, MqttActionListener)}
*
* When building an application,
* the design of the topic tree should take into account the following principles
* of topic name syntax and semantics:
*
*
* - A topic must be at least one character long.
* - Topic names are case sensitive. For example, ACCOUNTS and Accounts are
* two different topics.
* - Topic names can include the space character. For example, Accounts
* payable is a valid topic.
* - A leading "/" creates a distinct topic. For example, /finance is
* different from finance. /finance matches "+/+" and "/+", but
* not "+".
* - Do not include the null character (Unicode
\x0000
) in
* any topic.
*
*
* The following principles apply to the construction and content of a topic
* tree:
*
*
* - The length is limited to 64k but within that there are no limits to the
* number of levels in a topic tree.
* - There can be any number of root nodes; that is, there can be any number
* of topic trees.
*
*
* @param topic the topic to use, for example "finance/stock/ibm".
* @return an MqttTopic object, which can be used to publish messages to
* the topic.
* @throws IllegalArgumentException if the topic contains a '+' or '#'
* wildcard character.
*/
public MqttTopic getTopic(String topic);
/**
* Determines if this client is currently connected to the server.
*
* @return true if connected, false otherwise.
*/
public boolean isConnected();
/**
* Returns the client ID used by this client.
* All clients connected to the
* same server or server farm must have a unique ID.
*
*
* @return the client ID used by this client.
*/
public String getClientId();
/**
* Returns the address of the server used by this client, as a URI.
* The format is the same as specified on the constructor.
*
*
* @return the server's address, as a URI String.
* @see MqttAsyncClient#MqttAsyncClient(String, String)
*/
public String getServerURI();
/**
* Returns the delivery tokens for any outstanding publish operations.
* If a client has been restarted and there are messages that were in the
* process of being delivered when the client stopped this method will
* return a token for each message enabling the delivery to be tracked
* Alternately the {@link MqttCallback#deliveryComplete(IMqttToken)}
* callback can be used to track the delivery of outstanding messages.
*
* If a client connects with cleanStart true then there will be no
* delivery tokens as the cleanStart option deletes all earlier state.
* For state to be remembered the client must connect with cleanStart
* set to false
* @return zero or more delivery tokens
*/
public IMqttToken[] getPendingTokens();
/**
* If manualAcks is set to true, then on completion of the messageArrived callback
* the MQTT acknowledgements are not sent. You must call messageArrivedComplete
* to send those acknowledgements. This allows finer control over when the acks are
* sent. The default behaviour, when manualAcks is false, is to send the MQTT
* acknowledgements automatically at the successful completion of the messageArrived
* callback method.
* @param manualAcks if set to true, MQTT acknowledgements are not sent.
*/
public void setManualAcks(boolean manualAcks);
/**
* Will attempt to reconnect to the server after the client has lost connection.
* @throws MqttException if an error occurs attempting to reconnect
*/
public void reconnect() throws MqttException;
/**
* Indicate that the application has completed processing the message with id messageId.
* This will cause the MQTT acknowledgement to be sent to the server.
* @param messageId the MQTT message id to be acknowledged
* @param qos the MQTT QoS of the message to be acknowledged
* @throws MqttException if there was a problem sending the acknowledgement
*/
public void messageArrivedComplete(int messageId, int qos) throws MqttException;
/**
* Close the client
* Releases all resource associated with the client. After the client has
* been closed it cannot be reused. For instance attempts to connect will fail.
* @throws MqttException if the client is not disconnected.
*/
public void close() throws MqttException;
}