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| --><h1 id="mqtt-protocol" tabindex="-1"><a class="header-anchor" href="#mqtt-protocol" aria-hidden="true">#</a> MQTT Protocol</h1><p><a href="http://mqtt.org/" target="_blank" rel="noopener noreferrer">MQTT<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a> is a machine-to-machine (M2M)/"Internet of Things" connectivity protocol.<br> It was designed as an extremely lightweight publish/subscribe messaging transport.<br> It is useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium.</p><p>IoTDB supports the MQTT v3.1(an OASIS Standard) protocol.<br> IoTDB server includes a built-in MQTT service that allows remote devices send messages into IoTDB server directly.</p><img style="width:100%;max-width:800px;max-height:600px;margin-left:auto;margin-right:auto;display:block;" src="https://alioss.timecho.com/docs/img/github/78357432-0c71cf80-75e4-11ea-98aa-c43a54d469ce.png"><h2 id="built-in-mqtt-service" tabindex="-1"><a class="header-anchor" href="#built-in-mqtt-service" aria-hidden="true">#</a> Built-in MQTT Service</h2><p>The Built-in MQTT Service provide the ability of direct connection to IoTDB through MQTT. It listen the publish messages from MQTT clients<br> and then write the data into storage immediately.<br> The MQTT topic corresponds to IoTDB timeseries.<br> The messages payload can be format to events by <code>PayloadFormatter</code> which loaded by java SPI, and the default implementation is <code>JSONPayloadFormatter</code>.<br> The default <code>json</code> formatter support two json format and its json array. The following is an MQTT message payload example:</p><div class="language-json line-numbers-mode" data-ext="json"><pre class="language-json"><code> <span class="token punctuation">{</span> |
| <span class="token property">"device"</span><span class="token operator">:</span><span class="token string">"root.sg.d1"</span><span class="token punctuation">,</span> |
| <span class="token property">"timestamp"</span><span class="token operator">:</span><span class="token number">1586076045524</span><span class="token punctuation">,</span> |
| <span class="token property">"measurements"</span><span class="token operator">:</span><span class="token punctuation">[</span><span class="token string">"s1"</span><span class="token punctuation">,</span><span class="token string">"s2"</span><span class="token punctuation">]</span><span class="token punctuation">,</span> |
| <span class="token property">"values"</span><span class="token operator">:</span><span class="token punctuation">[</span><span class="token number">0.530635</span><span class="token punctuation">,</span><span class="token number">0.530635</span><span class="token punctuation">]</span> |
| <span class="token punctuation">}</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>or</p><div class="language-json line-numbers-mode" data-ext="json"><pre class="language-json"><code> <span class="token punctuation">{</span> |
| <span class="token property">"device"</span><span class="token operator">:</span><span class="token string">"root.sg.d1"</span><span class="token punctuation">,</span> |
| <span class="token property">"timestamps"</span><span class="token operator">:</span><span class="token punctuation">[</span><span class="token number">1586076045524</span><span class="token punctuation">,</span><span class="token number">1586076065526</span><span class="token punctuation">]</span><span class="token punctuation">,</span> |
| <span class="token property">"measurements"</span><span class="token operator">:</span><span class="token punctuation">[</span><span class="token string">"s1"</span><span class="token punctuation">,</span><span class="token string">"s2"</span><span class="token punctuation">]</span><span class="token punctuation">,</span> |
| <span class="token property">"values"</span><span class="token operator">:</span><span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token number">0.530635</span><span class="token punctuation">,</span><span class="token number">0.530635</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token number">0.530655</span><span class="token punctuation">,</span><span class="token number">0.530695</span><span class="token punctuation">]</span><span class="token punctuation">]</span> |
| <span class="token punctuation">}</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>or json array of the above two.</p><img style="width:100%;max-width:800px;max-height:600px;margin-left:auto;margin-right:auto;display:block;" src="https://alioss.timecho.com/docs/img/github/78357469-1bf11880-75e4-11ea-978f-a53996667a0d.png"><h2 id="mqtt-configurations" tabindex="-1"><a class="header-anchor" href="#mqtt-configurations" aria-hidden="true">#</a> MQTT Configurations</h2><p>The IoTDB MQTT service load configurations from <code>${IOTDB_HOME}/${IOTDB_CONF}/iotdb-common.properties</code> by default.</p><p>Configurations are as follows:</p><table><thead><tr><th>NAME</th><th style="text-align:center;">DESCRIPTION</th><th style="text-align:center;">DEFAULT</th></tr></thead><tbody><tr><td>enable_mqtt_service</td><td style="text-align:center;">whether to enable the mqtt service</td><td style="text-align:center;">false</td></tr><tr><td>mqtt_host</td><td style="text-align:center;">the mqtt service binding host</td><td style="text-align:center;">127.0.0.1</td></tr><tr><td>mqtt_port</td><td style="text-align:center;">the mqtt service binding port</td><td style="text-align:center;">1883</td></tr><tr><td>mqtt_handler_pool_size</td><td style="text-align:center;">the handler pool size for handing the mqtt messages</td><td style="text-align:center;">1</td></tr><tr><td>mqtt_payload_formatter</td><td style="text-align:center;">the mqtt message payload formatter</td><td style="text-align:center;">json</td></tr><tr><td>mqtt_max_message_size</td><td style="text-align:center;">the max mqtt message size in byte</td><td style="text-align:center;">1048576</td></tr></tbody></table><h2 id="coding-examples" tabindex="-1"><a class="header-anchor" href="#coding-examples" aria-hidden="true">#</a> Coding Examples</h2><p>The following is an example which a mqtt client send messages to IoTDB server.</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">MQTT</span> mqtt <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">MQTT</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| mqtt<span class="token punctuation">.</span><span class="token function">setHost</span><span class="token punctuation">(</span><span class="token string">"127.0.0.1"</span><span class="token punctuation">,</span> <span class="token number">1883</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| mqtt<span class="token punctuation">.</span><span class="token function">setUserName</span><span class="token punctuation">(</span><span class="token string">"root"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| mqtt<span class="token punctuation">.</span><span class="token function">setPassword</span><span class="token punctuation">(</span><span class="token string">"root"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| |
| <span class="token class-name">BlockingConnection</span> connection <span class="token operator">=</span> mqtt<span class="token punctuation">.</span><span class="token function">blockingConnection</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| connection<span class="token punctuation">.</span><span class="token function">connect</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| |
| <span class="token class-name">Random</span> random <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Random</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> <span class="token number">10</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token class-name">String</span> payload <span class="token operator">=</span> <span class="token class-name">String</span><span class="token punctuation">.</span><span class="token function">format</span><span class="token punctuation">(</span><span class="token string">"{\n"</span> <span class="token operator">+</span> |
| <span class="token string">"\"device\":\"root.sg.d1\",\n"</span> <span class="token operator">+</span> |
| <span class="token string">"\"timestamp\":%d,\n"</span> <span class="token operator">+</span> |
| <span class="token string">"\"measurements\":[\"s1\"],\n"</span> <span class="token operator">+</span> |
| <span class="token string">"\"values\":[%f]\n"</span> <span class="token operator">+</span> |
| <span class="token string">"}"</span><span class="token punctuation">,</span> <span class="token class-name">System</span><span class="token punctuation">.</span><span class="token function">currentTimeMillis</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> random<span class="token punctuation">.</span><span class="token function">nextDouble</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| |
| connection<span class="token punctuation">.</span><span class="token function">publish</span><span class="token punctuation">(</span><span class="token string">"root.sg.d1.s1"</span><span class="token punctuation">,</span> payload<span class="token punctuation">.</span><span class="token function">getBytes</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token class-name">QoS</span><span class="token punctuation">.</span><span class="token constant">AT_LEAST_ONCE</span><span class="token punctuation">,</span> <span class="token boolean">false</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| |
| connection<span class="token punctuation">.</span><span class="token function">disconnect</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="customize-your-mqtt-message-format" tabindex="-1"><a class="header-anchor" href="#customize-your-mqtt-message-format" aria-hidden="true">#</a> Customize your MQTT Message Format</h2><p>If you do not like the above Json format, you can customize your MQTT Message format by just writing several lines<br> of codes. An example can be found in <code>example/mqtt-customize</code> project.</p><p>Steps:</p><ul><li>Create a java project, and add dependency:</li></ul><div class="language-xml line-numbers-mode" data-ext="xml"><pre class="language-xml"><code> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>dependency</span><span class="token punctuation">></span></span> |
| <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>groupId</span><span class="token punctuation">></span></span>org.apache.iotdb<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>groupId</span><span class="token punctuation">></span></span> |
| <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>artifactId</span><span class="token punctuation">></span></span>iotdb-server<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>artifactId</span><span class="token punctuation">></span></span> |
| <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>version</span><span class="token punctuation">></span></span>1.1.0-SNAPSHOT<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>version</span><span class="token punctuation">></span></span> |
| <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>dependency</span><span class="token punctuation">></span></span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><ul><li>Define your implementation which implements <code>org.apache.iotdb.db.protocol.mqtt.PayloadFormatter</code><br> e.g.,</li></ul><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">package</span> <span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>mqtt<span class="token punctuation">.</span>server</span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">io<span class="token punctuation">.</span>netty<span class="token punctuation">.</span>buffer<span class="token punctuation">.</span></span><span class="token class-name">ByteBuf</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>db<span class="token punctuation">.</span>protocol<span class="token punctuation">.</span>mqtt<span class="token punctuation">.</span></span><span class="token class-name">Message</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>db<span class="token punctuation">.</span>protocol<span class="token punctuation">.</span>mqtt<span class="token punctuation">.</span></span><span class="token class-name">PayloadFormatter</span></span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">java<span class="token punctuation">.</span>nio<span class="token punctuation">.</span>charset<span class="token punctuation">.</span></span><span class="token class-name">StandardCharsets</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">java<span class="token punctuation">.</span>util<span class="token punctuation">.</span></span><span class="token class-name">ArrayList</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">java<span class="token punctuation">.</span>util<span class="token punctuation">.</span></span><span class="token class-name">Arrays</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">java<span class="token punctuation">.</span>util<span class="token punctuation">.</span></span><span class="token class-name">List</span></span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">CustomizedJsonPayloadFormatter</span> <span class="token keyword">implements</span> <span class="token class-name">PayloadFormatter</span> <span class="token punctuation">{</span> |
| |
| <span class="token annotation punctuation">@Override</span> |
| <span class="token keyword">public</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">Message</span><span class="token punctuation">></span></span> <span class="token function">format</span><span class="token punctuation">(</span><span class="token class-name">ByteBuf</span> payload<span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token comment">// Suppose the payload is a json format</span> |
| <span class="token keyword">if</span> <span class="token punctuation">(</span>payload <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token keyword">return</span> <span class="token keyword">null</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| |
| <span class="token class-name">String</span> json <span class="token operator">=</span> payload<span class="token punctuation">.</span><span class="token function">toString</span><span class="token punctuation">(</span><span class="token class-name">StandardCharsets</span><span class="token punctuation">.</span><span class="token constant">UTF_8</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token comment">// parse data from the json and generate Messages and put them into List<Meesage> ret</span> |
| <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">Message</span><span class="token punctuation">></span></span> ret <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ArrayList</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token comment">// this is just an example, so we just generate some Messages directly</span> |
| <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> <span class="token number">2</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token keyword">long</span> ts <span class="token operator">=</span> i<span class="token punctuation">;</span> |
| <span class="token class-name">Message</span> message <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Message</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| message<span class="token punctuation">.</span><span class="token function">setDevice</span><span class="token punctuation">(</span><span class="token string">"d"</span> <span class="token operator">+</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span> |
| message<span class="token punctuation">.</span><span class="token function">setTimestamp</span><span class="token punctuation">(</span>ts<span class="token punctuation">)</span><span class="token punctuation">;</span> |
| message<span class="token punctuation">.</span><span class="token function">setMeasurements</span><span class="token punctuation">(</span><span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">asList</span><span class="token punctuation">(</span><span class="token string">"s1"</span><span class="token punctuation">,</span> <span class="token string">"s2"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| message<span class="token punctuation">.</span><span class="token function">setValues</span><span class="token punctuation">(</span><span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">asList</span><span class="token punctuation">(</span><span class="token string">"4.0"</span> <span class="token operator">+</span> i<span class="token punctuation">,</span> <span class="token string">"5.0"</span> <span class="token operator">+</span> i<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| ret<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>message<span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| <span class="token keyword">return</span> ret<span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| |
| <span class="token annotation punctuation">@Override</span> |
| <span class="token keyword">public</span> <span class="token class-name">String</span> <span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token comment">// set the value of mqtt_payload_formatter in iotdb-datanode.properties as the following string:</span> |
| <span class="token keyword">return</span> <span class="token string">"CustomizedJson"</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| <span class="token punctuation">}</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><ul><li>modify the file in <code>src/main/resources/META-INF/services/org.apache.iotdb.db.protocol.mqtt.PayloadFormatter</code>:<br> clean the file and put your implementation class name into the file.<br> In this example, the content is: <code>org.apache.iotdb.mqtt.server.CustomizedJsonPayloadFormatter</code></li><li>compile your implementation as a jar file: <code>mvn package -DskipTests</code></li></ul><p>Then, in your server:</p><ul><li>Create ${IOTDB_HOME}/ext/mqtt/ folder, and put the jar into this folder.</li><li>Update configuration to enable MQTT service. (<code>enable_mqtt_service=true</code> in <code>conf/iotdb-datanode.properties</code>)</li><li>Set the value of <code>mqtt_payload_formatter</code> in <code>conf/iotdb-datanode.properties</code> as the value of getName() in your implementation<br> , in this example, the value is <code>CustomizedJson</code></li><li>Launch the IoTDB server.</li><li>Now IoTDB will use your implementation to parse the MQTT message.</li></ul><p>More: the message format can be anything you want. For example, if it is a binary format,<br> just use <code>payload.forEachByte()</code> or <code>payload.array</code> to get bytes content.</p></div><!--[--><!----><!--]--><footer class="page-meta"><div class="meta-item edit-link"><a href="https://github.com/apache/iotdb-docs/edit/main/src/UserGuide/V1.2.x/API/Programming-MQTT.md" rel="noopener noreferrer" target="_blank" aria-label="Found Error? 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