package org.eclipse.paho.client.mqttv3;
/**
* Enables an application to communicate with an MQTT server using using blocking methods.
* <p>
* This interface allows applications to utilize all features of the MQTT version 3.1
* specification including:
* <ul>
* <li>connect
* <li>publish
* <li>subscribe
* <li>unsubscribe
* <li>disconnect
* </ul>
* </p>
* <p>
* There are two styles of MQTT client, this one and {@link IMqttAsyncClient}.
* <ul>
* <li>IMqttClient provides a set of methods that block and return control to the application
* program once the MQTT action has completed.</li>
* <li>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.</li>
* </ul>
* </p>
* <p>
* 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:
* <code><pre>
* IMqttToken token;
* token = asyncClient.method(parms).waitForCompletion();
* </pre></code>
* 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.</p>
*/
public interface IMqttClient { //extends IMqttAsyncClient {
/**
* Connects to an MQTT server using the default options.
* <p>The default options are specified in {@link MqttConnectOptions} class.
* </p>
*
* @throws MqttSecurityException when the server rejects the connect for security
* reasons
* @throws MqttException for non security related problems
* @see #connect(MqttConnectOptions)
*/
public void connect() throws MqttSecurityException, MqttException;
/**
* Connects to an MQTT server using the specified options.
* <p>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.
* </p>
* <p>This is a blocking method that returns once connect completes</p>
*
* @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(MqttConnectOptions options) throws MqttSecurityException, MqttException;
/**
* Disconnects from the server.
* <p>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.
* </p>
*
* @see #disconnect(long)
*/
public void disconnect() throws MqttException;
/**
* Disconnects from the server.
* <p>
* 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 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.</p>
*
* <p>This is a blocking method that returns once disconnect completes</p>
*
* @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;
/**
* Subscribe to a topic, which may include wildcards using a QoS of 1.
*
* @see #subscribe(String[], int[])
*
* @param topicFilter the topic to subscribe to, which can include wildcards.
* @throws MqttException if there was an error registering the subscription.
*/
public void subscribe(String topicFilter) throws MqttException, MqttSecurityException;
/**
* Subscribes to a one or more topics, which may include wildcards using a QoS of 1.
*
* @see #subscribe(String[], int[])
*
* @param topicFilters the topic to subscribe to, which can include wildcards.
* @throws MqttException if there was an error registering the subscription.
*/
public void subscribe(String[] topicFilters) 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.
* @throws MqttException if there was an error registering the subscription.
*/
public void subscribe(String topicFilter, int qos) throws MqttException;
/**
* Subscribes to multiple topics, each of which may include wildcards.
* <p>The {@link #setCallback(MqttCallback)} method
* should be called before this method, otherwise any received messages
* will be discarded.
* </p>
* <p>
* If (@link MqttConnectOptions#setCleanSession(boolean)} was set to true
* when when connecting to the server then the subscription remains in place
* until either:
* <ul>
* <li>The client disconnects</li>
* <li>An unsubscribe method is called to un-subscribe the topic</li>
* </li>
* </p>
* <p>
* If (@link MqttConnectOptions#setCleanSession(boolean)} was set to false
* when when connecting to the server then the subscription remains in place
* until either:
* <ul>
* <li>An unsubscribe method is called to unsubscribe the topic</li>
* <li>The client connects with cleanSession set to true</ul>
* </li>
* With cleanSession 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 <bold>same client ID</bold> the server will
* deliver the stored messages to the client.
* </p>
*
* <p>The "topic filter" string used when subscribing
* may contain special characters, which allow you to subscribe to multiple topics
* at once.</p>
* <p>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.
* <dl>
* <dt>Topic level separator</dt>
* <dd>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.</dd>
*
* <dt>Multi-level wildcard</dt>
* <dd><p>The number sign (#) is a wildcard character that matches
* any number of levels within a topic. For example, if you subscribe to
* <span><span class="filepath">finance/stock/ibm/#</span></span>, you receive
* messages on these topics:
* <pre> finance/stock/ibm<br /> finance/stock/ibm/closingprice<br /> finance/stock/ibm/currentprice</pre>
* </p>
* <p>The multi-level wildcard
* can represent zero or more levels. Therefore, <em>finance/#</em> can also match
* the singular <em>finance</em>, where <em>#</em> represents zero levels. The topic
* level separator is meaningless in this context, because there are no levels
* to separate.</p>
*
* <p>The <span>multi-level</span> wildcard can
* be specified only on its own or next to the topic level separator character.
* Therefore, <em>#</em> and <em>finance/#</em> are both valid, but <em>finance#</em> is
* not valid. <span>The multi-level wildcard must be the last character
* used within the topic tree. For example, <em>finance/#</em> is valid but
* <em>finance/#/closingprice</em> is not valid.</span></p></dd>
*
* <dt>Single-level wildcard</dt>
* <dd><p>The plus sign (+) is a wildcard character that matches only one topic
* level. For example, <em>finance/stock/+</em> matches
* <em>finance/stock/ibm</em> and <em>finance/stock/xyz</em>,
* but not <em>finance/stock/ibm/closingprice</em>. Also, because the single-level
* wildcard matches only a single level, <em>finance/+</em> does not match <em>finance</em>.</p>
*
* <p>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,
* <em>+</em> and <em>finance/+</em> are both valid, but <em>finance+</em> is
* not valid. <span>The single-level wildcard can be used at the end of the
* topic tree or within the topic tree.
* For example, <em>finance/+</em> and <em>finance/+/ibm</em> are both valid.</span></p>
* </dd>
* </dl>
* </p>
*
* <p>This is a blocking method that returns once subscribe completes</p>
*
* @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.
* @throws MqttException if there was an error registering the subscription.
* @throws IllegalArgumentException if the two supplied arrays are not the same size.
*/
public void subscribe(String[] topicFilters, int[] qos) 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.
* <p>
* 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.
* </p>
* <p>The topic(s) specified on the unsubscribe must match the topic(s)
* specified in the original subscribe request for the subscribe to succeed
* </p>
*
* <p>This is a blocking method that returns once unsubscribe completes</p>
*
* @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.
* <p>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.
* </p>
*
* @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.
* <p>
* 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:
* <ul>
* <li>The connection is re-established with the same clientID
* <li>The original connection was made with (@link MqttConnectOptions#setCleanSession(boolean)}
* set to false
* <li>The connection is re-established with (@link MqttConnectOptions#setCleanSession(boolean)}
* set to false
* </ul>
* </p>
* <p>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:
* <ul>
* <li>Register a {@link #setCallback(MqttCallback)} callback on the client and the delivery complete
* callback will be notified once a delivery of a message completes
* <li>or call {@link #getPendingDeliveryTokens()} which will return a token for each message that
* is in-flight. The token can be used to wait for delivery to complete.
* </ul>
* </p>
*
* <p>When building an application,
* the design of the topic tree should take into account the following principles
* of topic name syntax and semantics:</p>
*
* <ul>
* <li>A topic must be at least one character long.</li>
* <li>Topic names are case sensitive. For example, <em>ACCOUNTS</em> and <em>Accounts</em> are
* two different topics.</li>
* <li>Topic names can include the space character. For example, <em>Accounts
* payable</em> is a valid topic.</li>
* <li>A leading "/" creates a distinct topic. For example, <em>/finance</em> is
* different from <em>finance</em>. <em>/finance</em> matches "+/+" and "/+", but
* not "+".</li>
* <li>Do not include the null character (Unicode<samp class="codeph"> \x0000</samp>) in
* any topic.</li>
* </ul>
*
* <p>The following principles apply to the construction and content of a topic
* tree:</p>
*
* <ul>
* <li>The length is limited to 64k but within that there are no limits to the
* number of levels in a topic tree.</li>
* <li>There can be any number of root nodes; that is, there can be any number
* of topic trees.</li>
* </ul>
* </p>
*
* <p>This is a blocking method that returns once publish completes</p> *
*
* @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 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.
*/
public void publish(String topic, MqttMessage message) throws MqttException, MqttPersistenceException;
/**
* Sets the callback listener to use for events that happen asynchronously.
* <p>There are a number of events that listener will be notified about. These include
* <ul>
* <li>A new message has arrived and is ready to be processed</li>
* <li>The connection to the server has been lost</li>
* <li>Delivery of a message to the server has completed.</li>
* </ul>
* </p>
* <p>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<p>
* @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.
* <p>An alternative method that should be used in preference to this one when publishing a message is:
* <ul>
* <li>{@link MqttClient#publish(String, MqttMessage)} to publish a message in a blocking manner
* <li>or use publish methods on the non-blocking client like {@link IMqttAsyncClient#publish(String, MqttMessage, Object, IMqttActionListener)}
* </ul>
* </p>
* <p>When building an application,
* the design of the topic tree should take into account the following principles
* of topic name syntax and semantics:</p>
*
* <ul>
* <li>A topic must be at least one character long.</li>
* <li>Topic names are case sensitive. For example, <em>ACCOUNTS</em> and <em>Accounts</em> are
* two different topics.</li>
* <li>Topic names can include the space character. For example, <em>Accounts
* payable</em> is a valid topic.</li>
* <li>A leading "/" creates a distinct topic. For example, <em>/finance</em> is
* different from <em>finance</em>. <em>/finance</em> matches "+/+" and "/+", but
* not "+".</li>
* <li>Do not include the null character (Unicode<samp class="codeph"> \x0000</samp>) in
* any topic.</li>
* </ul>
*
* <p>The following principles apply to the construction and content of a topic
* tree:</p>
*
* <ul>
* <li>The length is limited to 64k but within that there are no limits to the
* number of levels in a topic tree.</li>
* <li>There can be any number of root nodes; that is, there can be any number
* of topic trees.</li>
* </ul>
* </p>
*
* @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 <code>true</code> if connected, <code>false</code> otherwise.
*/
public boolean isConnected();
/**
* Returns the client ID used by this client.
* <p>All clients connected to the
* same server or server farm must have a unique ID.
* </p>
*
* @return the client ID used by this client.
*/
public String getClientId();
/**
* Returns the address of the server used by this client, as a URI.
* <p>The format is the same as specified on the constructor.
* </p>
*
* @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.
* <p>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(IMqttDeliveryToken)}
* callback can be used to track the delivery of outstanding messages.
* </p>
* <p>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</P>
* @return zero or more delivery tokens
*/
public IMqttDeliveryToken[] getPendingDeliveryTokens();
/**
* 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;
}