signalk-server

Version:

An implementation of a [Signal K](http://signalk.org) server for boats.

71 lines (62 loc) • 22.1 kB

HTML

<!DOCTYPE html><html class="default" lang="en" data-base="../../"><head><meta charset="utf-8"/><meta http-equiv="x-ua-compatible" content="IE=edge"/><title>Processing Data | Signal K</title><meta name="description" content="Documentation for Signal K"/><meta name="viewport" content="width=device-width, initial-scale=1"/><link rel="stylesheet" href="../../assets/style.css?cache=1767726585343"/><link rel="stylesheet" href="../../assets/highlight.css?cache=1767726585343"/><script defer src="../../assets/main.js?cache=1767726585343"></script><script async src="../../assets/icons.js?cache=1767726585343" id="tsd-icons-script"></script><script async src="../../assets/search.js?cache=1767726585343" id="tsd-search-script"></script><script async src="../../assets/navigation.js?cache=1767726585343" id="tsd-nav-script"></script><script async src="../../assets/hierarchy.js?cache=1767726585343" id="tsd-hierarchy-script"></script><link rel="stylesheet" href="../../assets/theme.css"/></head><body><script>document.documentElement.dataset.theme = localStorage.getItem("tsd-theme") || "os";document.body.style.display="none";setTimeout(() => window.app?app.showPage():document.body.style.removeProperty("display"),500)</script><header class="tsd-page-toolbar"><div class="tsd-toolbar-contents container"><a href="../../index.html" class="title"><img src="../../assets/logo.svg" alt="Signal K"/></a><button id="tsd-search-trigger" class="tsd-widget" aria-label="Search"><svg width="16" height="16" viewBox="0 0 16 16" fill="none" aria-hidden="true"><use href="../../assets/icons.svg#icon-search"></use></svg>Search</button><dialog id="tsd-search" aria-label="Search"><input role="combobox" id="tsd-search-input" aria-controls="tsd-search-results" aria-autocomplete="list" aria-expanded="true" autocapitalize="off" autocomplete="off" placeholder="Search the docs" maxLength="100"/><ul role="listbox" id="tsd-search-results"></ul><div id="tsd-search-status" aria-live="polite" aria-atomic="true"><div>Preparing search index...</div></div></dialog><div id="tsd-toolbar-links"><a href="https://discord.gg/uuZrwz4dCS" target="_blank" rel="noopener" class="toolbar-icon visible@s" aria-label="Discord"><svg width="24" height="24" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 640 512"><path d="M524.5 69.8a1.5 1.5 0 0 0 -.8-.7A485.1 485.1 0 0 0 404.1 32a1.8 1.8 0 0 0 -1.9 .9 337.5 337.5 0 0 0 -14.9 30.6 447.8 447.8 0 0 0 -134.4 0 309.5 309.5 0 0 0 -15.1-30.6 1.9 1.9 0 0 0 -1.9-.9A483.7 483.7 0 0 0 116.1 69.1a1.7 1.7 0 0 0 -.8 .7C39.1 183.7 18.2 294.7 28.4 404.4a2 2 0 0 0 .8 1.4A487.7 487.7 0 0 0 176 479.9a1.9 1.9 0 0 0 2.1-.7A348.2 348.2 0 0 0 208.1 430.4a1.9 1.9 0 0 0 -1-2.6 321.2 321.2 0 0 1 -45.9-21.9 1.9 1.9 0 0 1 -.2-3.1c3.1-2.3 6.2-4.7 9.1-7.1a1.8 1.8 0 0 1 1.9-.3c96.2 43.9 200.4 43.9 295.5 0a1.8 1.8 0 0 1 1.9 .2c2.9 2.4 6 4.9 9.1 7.2a1.9 1.9 0 0 1 -.2 3.1 301.4 301.4 0 0 1 -45.9 21.8 1.9 1.9 0 0 0 -1 2.6 391.1 391.1 0 0 0 30 48.8 1.9 1.9 0 0 0 2.1 .7A486 486 0 0 0 610.7 405.7a1.9 1.9 0 0 0 .8-1.4C623.7 277.6 590.9 167.5 524.5 69.8zM222.5 337.6c-29 0-52.8-26.6-52.8-59.2S193.1 219.1 222.5 219.1c29.7 0 53.3 26.8 52.8 59.2C275.3 311 251.9 337.6 222.5 337.6zm195.4 0c-29 0-52.8-26.6-52.8-59.2S388.4 219.1 417.9 219.1c29.7 0 53.3 26.8 52.8 59.2C470.7 311 447.5 337.6 417.9 337.6z"></path></svg></a><a href="https://github.com/SignalK/signalk-server" target="_blank" rel="noopener" class="toolbar-icon visible@s" aria-label="Discord"><svg width="24" height="24" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 496 512"><path d="M165.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3 .3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6zm-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5 .3-6.2 2.3zm44.2-1.7c-2.9 .7-4.9 2.6-4.6 4.9 .3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9zM244.8 8C106.1 8 0 113.3 0 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C428.2 457.8 496 362.9 496 252 496 113.3 383.5 8 244.8 8zM97.2 352.9c-1.3 1-1 3.3 .7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1zm-10.8-8.1c-.7 1.3 .3 2.9 2.3 3.9 1.6 1 3.6 .7 4.3-.7 .7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3 .7zm32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3 .7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1zm-11.4-14.7c-1.6 1-1.6 3.6 0 5.9 1.6 2.3 4.3 3.3 5.6 2.3 1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2z"></path></svg></a><a href="#" class="tsd-widget menu" id="tsd-toolbar-menu-trigger" data-toggle="menu" aria-label="Menu"><svg width="16" height="16" viewBox="0 0 16 16" fill="none" aria-hidden="true"><use href="../../assets/icons.svg#icon-menu"></use></svg></a></div></div></header><div class="container container-main"><div class="col-content"><div class="tsd-page-title"><ul class="tsd-breadcrumb" aria-label="Breadcrumb"><li><a href="../../Developing.html">Developing</a></li><li><a href="../Plugins.html">Plugins</a></li><li><a href="" aria-current="page">Processing Data</a></li></ul></div><div class="tsd-panel tsd-typography"><h1 id="processing-data-from-the-server" class="tsd-anchor-link">Processing data from the server<a href="#processing-data-from-the-server" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../assets/icons.svg#icon-anchor"></use></svg></a></h1>A plugin will generally want to: <ol> <li>Subscribe to data published by the server (i.e. received from a NMEA 2000 bus, etc)</li> <li>Emit data.</li> </ol> In both cases the plugin will use deltas which the server uses to signal changes in the Signal K full data model. Delta messages contain the new value associated with a path (not the amount of change from the previous value.)_ See the <a href="http://signalk.org/specification/1.7.0/doc/data_model.html#delta-format">Signal K Delta Specification</a> for details. Using the server API, plugins can either: <ol> <li>Get the current value of a path in the full model or</li> <li>Subscribe to a path and access a stream of deltas that updates every time the value is updated.</li> </ol> By specifying a context e.g. 'vessels.self' you can limit the number of delta messages received to those of host vesseel. To receive all deltas you can specify <code>*</code> as the context. You can also limit the deltas received by the path you supply. If you supply a specific path e.g. navigation.position, only updates in the value will be received. Since paths are hierarchical, paths can contain wildcards e.g._navigation.* which will deliver deltas containing updates to all paths under <code>navigation</code>. The data received is formatted as per the following example: <pre><code class="javascript"> { path: 'navigation.position', value: { longitude: 24.7366117, latitude: 59.72493 }, context: 'vessel.self', source: { label: 'n2k-sample-data', type: 'NMEA2000', pgn: 129039, src: '43' }, $source: 'n2k-sample-data.43', timestamp: '2014-08-15T19:00:02.392Z' } </code><button type="button">Copy</button></pre> <h2 id="reading-the-current-path-value" class="tsd-anchor-link">Reading the current path value<a href="#reading-the-current-path-value" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../assets/icons.svg#icon-anchor"></use></svg></a></h2>The server API provides the following methods for retrieving values from the full data model. <ul> <li><code>getSelfPath(path)</code> returns the value of the supplied <code>path</code> in the <code>vessels.self</code> context.</li> </ul> <pre><code class="javascript">const value = app.getSelfPath('uuid') app.debug(value) // Should output something like urn:mrn:signalk:uuid:a9d2c3b1-611b-4b00-8628-0b89d014ed60 </code><button type="button">Copy</button></pre> <ul> <li><code>getPath(path)</code> returns the value of the path (including the context) starting from the root of the full data model.</li> </ul> <pre><code class="javascript">const baseStations = app.getPath('shore.basestations') </code><button type="button">Copy</button></pre> <h2 id="subscribing-to-deltas" class="tsd-anchor-link">Subscribing to Deltas<a href="#subscribing-to-deltas" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../assets/icons.svg#icon-anchor"></use></svg></a></h2>A can subscribe to a stream of updates (deltas) by creating the subscription. Subcriptions are generally manged in the plugin <code>start()</code> and <code>stop()</code> methods to ensure the subscribtions are unsubscribed prior to the plugin stopping to ensure all resources are freed. The following example illustrates the pattern using the <a href="../../_signalk/server-api/ServerAPI.html#subscriptionmanager" class="tsd-kind-property"><code>subscriptionmanager</code></a> API method. <pre><code class="javascript">let unsubscribes = [] plugin.start = (options, restartPlugin) => { app.debug('Plugin started') let localSubscription = { context: '*', // Get data for all contexts subscribe: [ { path: '*', // Get all paths period: 5000 // Every 5000ms } ] } app.subscriptionmanager.subscribe( localSubscription, unsubscribes, (subscriptionError) => { app.error('Error:' + subscriptionError) }, (delta) => { delta.updates.forEach((u) => { app.debug(u) }) } ) } plugin.stop = () => { unsubscribes.forEach((f) => f()) unsubscribes = [] } </code><button type="button">Copy</button></pre> In the <code>start()</code> method create a subscription definition <code>localSubscription</code> which is then passed to <code>app.subscriptionmanager.subscribe()</code> as the first argument, we also pass the <code>unsubscribes</code> array in the second argument. The third argument is a function that will be called when there's an error. The final argument is a function that will be called every time an update is received. In the <code>stop()</code> method each subcription in the <code>unsubscribes</code> array is unsubscribed and the resources released. <h2 id="sending-deltas" class="tsd-anchor-link">Sending Deltas<a href="#sending-deltas" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../assets/icons.svg#icon-anchor"></use></svg></a></h2>A SignalK plugin can not only read deltas, but can also send them. This is done using the <code>handleMessage()</code> API method and supplying: <ol> <li>The plugin id</li> <li>A formatted delta update message</li> <li>The Signal K version ['v1' or 'v2'] (if omitted the default is 'v1'). See <a href="../REST_APIs.html">REST APIs</a> for details.</li> </ol> Example: <pre><code class="javascript">app.handleMessage( plugin.id, { updates: [ { values: [ { path: 'environment.outside.temperature', value: -253 } ] } ] }, 'v1' ) </code><button type="button">Copy</button></pre> <h2 id="sending-nmea-2000-data-from-a-plugin" class="tsd-anchor-link">Sending NMEA 2000 data from a plugin<a href="#sending-nmea-2000-data-from-a-plugin" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../assets/icons.svg#icon-anchor"></use></svg></a></h2>A SignalK plugin can not only emit deltas, but can also send data such as NMEA 2000 data. This is done using the <code>emit()</code> API and specifying the provider as well as the formatted data to send. Example: Send NMEA using Actisense serial format: <pre><code class="javascript">app.emit( 'nmea2000out', '2017-04-15T14:57:58.468Z,0,262384,0,0,14,01,0e,00,88,b6,02,00,00,00,00,00,a2,08,00' ) </code><button type="button">Copy</button></pre> Example: Send NMEA using Canboat JSON format: <pre><code class="javascript">app.emit('nmea2000JsonOut', { pgn: 130306, 'Wind Speed': speed, 'Wind Angle': angle < 0 ? angle + Math.PI * 2 : angle, Reference: 'Apparent' }) </code><button type="button">Copy</button></pre> <h3 id="sending-a-message-on-nmea2000-startup" class="tsd-anchor-link">Sending a message on NMEA2000 startup<a href="#sending-a-message-on-nmea2000-startup" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../assets/icons.svg#icon-anchor"></use></svg></a></h3>If you need to send an NMEA2000 message out at startup, e.g get current state from a device you will need to wait until the provider is ready before sending your message. Example: Send NMEA after the provider is ready: <pre><code class="javascript">app.on('nmea2000OutAvailable', () => { app.emit( 'nmea2000out', '2017-04-15T14:57:58.468Z,2,6,126720,%s,%s,4,a3,99,01,00' ) }) </code><button type="button">Copy</button></pre> </div></div><div class="col-sidebar"><div class="page-menu"><details open class="tsd-accordion tsd-page-navigation"><summary class="tsd-accordion-summary"><svg width="20" height="20" viewBox="0 0 24 24" fill="none" aria-hidden="true"><use href="../../assets/icons.svg#icon-chevronDown"></use></svg><h3>On This Page</h3></summary><div class="tsd-accordion-details"><a href="#reading-the-current-path-value">Reading the current path value</a><a href="#subscribing-to-deltas">Subscribing to Deltas</a><a href="#sending-deltas">Sending Deltas</a><a href="#sending-nmea-2000-data-from-a-plugin">Sending NMEA 2000 data from a plugin</a><ul><li><a href="#sending-a-message-on-nmea2000-startup">Sending a message on NMEA2000 startup</a></li></ul></div></details></div><div class="site-menu"><nav class="tsd-navigation"><a href="../../modules.html">Signal K</a><ul class="tsd-small-nested-navigation" id="tsd-nav-container"><li>Loading...</li></ul></nav></div></div></div><footer>Generated using <a href="https://typedoc.org/" target="_blank">TypeDoc</a></footer><div class="overlay"></div></body></html>