signalk-server

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aria-current="page">Integration Guide for WASM Plugins</a></li></ul></div><div class="tsd-panel tsd-typography"><h1 id="integration-guide-for-wasm-plugins" class="tsd-anchor-link">Integration Guide for WASM Plugins<a href="#integration-guide-for-wasm-plugins" 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> <h2 id="static-file-serving" class="tsd-anchor-link">Static File Serving<a href="#static-file-serving" 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> Plugins can serve HTML, CSS, JavaScript and other static files: Structure: <pre><code>@signalk/my-plugin/ ├── public/ # Automatically served at /plugins/my-plugin/ │ ├── index.html │ ├── style.css │ └── app.js ├── plugin.wasm └── package.json </code><button>Copy</button></pre> Access: <code>http://localhost:3000/plugins/my-plugin/</code> serves <code>public/index.html</code> <h2 id="resource-providers" class="tsd-anchor-link">Resource Providers<a href="#resource-providers" 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> WASM plugins can act as resource providers for Signal K resources like weather data, routes, waypoints, or custom resource types. <h3 id="enabling-resource-provider-capability" class="tsd-anchor-link">Enabling Resource Provider Capability<a href="#enabling-resource-provider-capability" 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> Add <code>resourceProvider: true</code> to your package.json: <pre><code class="json">{ "wasmCapabilities": { "network": true, "dataRead": true, "dataWrite": true, "resourceProvider": true } } </code><button type="button">Copy</button></pre> <h3 id="registering-as-a-resource-provider" class="tsd-anchor-link">Registering as a Resource Provider<a href="#registering-as-a-resource-provider" 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> <h4 id="assemblyscript" class="tsd-anchor-link">AssemblyScript<a href="#assemblyscript" 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></h4> <pre><code class="typescript">import { registerResourceProvider } from '@signalk/assemblyscript-plugin-sdk/assembly/resources' // In plugin start(): if (!registerResourceProvider('weather-forecasts')) { setError('Failed to register as resource provider') return 1 } </code><button type="button">Copy</button></pre> <h4 id="rust" class="tsd-anchor-link">Rust<a href="#rust" 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></h4> <pre><code class="rust">#[link(wasm_import_module = "env")] extern "C" { fn sk_register_resource_provider(type_ptr: *const u8, type_len: usize) -> i32; } pub fn register_resource_provider(resource_type: &str) -> bool { let bytes = resource_type.as_bytes(); unsafe { sk_register_resource_provider(bytes.as_ptr(), bytes.len()) == 1 } } // In plugin_start(): if !register_resource_provider("weather-forecasts") { // Registration failed return 1; } </code><button type="button">Copy</button></pre> <h3 id="implementing-resource-handlers" class="tsd-anchor-link">Implementing Resource Handlers<a href="#implementing-resource-handlers" 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> After registering, your plugin must export these handler functions: <h4 id="-list-resources-matching-a-query" class="tsd-anchor-link"><code>resources_list_resources</code> - List resources matching a query<a href="#-list-resources-matching-a-query" 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></h4> AssemblyScript: <pre><code class="typescript">export function resources_list_resources(queryJson: string): string { // queryJson: {"bbox": [...], "distance": 1000, ...} // Return JSON object: {"resource-id-1": {...}, "resource-id-2": {...}} return '{"forecast-1": {"name": "Current Weather", "type": "weather"}}' } </code><button type="button">Copy</button></pre> Rust: <pre><code class="rust">#[no_mangle] pub extern "C" fn resources_list_resources( request_ptr: *const u8, request_len: usize, response_ptr: *mut u8, response_max_len: usize, ) -> i32 { // Parse query, build response let response = r#"{"forecast-1": {"name": "Current Weather"}}"#; write_string(response, response_ptr, response_max_len) } </code><button type="button">Copy</button></pre> <h4 id="-get-a-single-resource" class="tsd-anchor-link"><code>resources_get_resource</code> - Get a single resource<a href="#-get-a-single-resource" 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></h4> AssemblyScript: <pre><code class="typescript">export function resources_get_resource(requestJson: string): string { // requestJson: {"id": "forecast-1", "property": null} return '{"name": "Current Weather", "temperature": 20.5, "humidity": 0.65}' } </code><button type="button">Copy</button></pre> <h4 id="-create-or-update-a-resource" class="tsd-anchor-link"><code>resources_set_resource</code> - Create or update a resource<a href="#-create-or-update-a-resource" 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></h4> AssemblyScript: <pre><code class="typescript">export function resources_set_resource(requestJson: string): string { // requestJson: {"id": "forecast-1", "value": {...}} // Return empty string on success, or error message return '' } </code><button type="button">Copy</button></pre> <h4 id="-delete-a-resource" class="tsd-anchor-link"><code>resources_delete_resource</code> - Delete a resource<a href="#-delete-a-resource" 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></h4> AssemblyScript: <pre><code class="typescript">export function resources_delete_resource(requestJson: string): string { // requestJson: {"id": "forecast-1"} return '' } </code><button type="button">Copy</button></pre> <h3 id="accessing-resources-via-http" class="tsd-anchor-link">Accessing Resources via HTTP<a href="#accessing-resources-via-http" 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> Once registered, resources are available at: <pre><code>GET /signalk/v2/api/resources/{type} # List all GET /signalk/v2/api/resources/{type}/{id} # Get one POST /signalk/v2/api/resources/{type}/{id} # Create/update DELETE /signalk/v2/api/resources/{type}/{id} # Delete </code><button>Copy</button></pre> <h3 id="standard-vs-custom-resource-types" class="tsd-anchor-link">Standard vs Custom Resource Types<a href="#standard-vs-custom-resource-types" 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> Signal K defines standard resource types with validation: <ul> <li><code>routes</code> - Navigation routes</li> <li><code>waypoints</code> - Navigation waypoints</li> <li><code>notes</code> - Freeform notes</li> <li><code>regions</code> - Geographic regions</li> <li><code>charts</code> - Chart metadata</li> </ul> Custom types (like <code>weather-forecasts</code>) have no schema validation and can contain any JSON structure. <h2 id="weather-providers" class="tsd-anchor-link">Weather Providers<a href="#weather-providers" 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> WASM plugins can act as weather providers for Signal K's specialized Weather API. <h3 id="weather-provider-vs-resource-provider" class="tsd-anchor-link">Weather Provider vs Resource Provider<a href="#weather-provider-vs-resource-provider" 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> <table> <thead> <tr> <th>Feature</th> <th>Weather Provider</th> <th>Resource Provider</th> </tr> </thead> <tbody> <tr> <td>API Path</td> <td><code>/signalk/v2/api/weather/*</code></td> <td><code>/signalk/v2/api/resources/{type}</code></td> </tr> <tr> <td>Methods</td> <td>getObservations, getForecasts, getWarnings</td> <td>list, get, set, delete</td> </tr> <tr> <td>Use Case</td> <td>Standardized weather data</td> <td>Generic data storage</td> </tr> <tr> <td>Capability</td> <td><code>weatherProvider: true</code></td> <td><code>resourceProvider: true</code></td> </tr> <tr> <td>FFI</td> <td><code>sk_register_weather_provider</code></td> <td><code>sk_register_resource_provider</code></td> </tr> </tbody> </table> <h3 id="enabling-weather-provider-capability" class="tsd-anchor-link">Enabling Weather Provider Capability<a href="#enabling-weather-provider-capability" 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> <pre><code class="json">{ "wasmCapabilities": { "network": true, "dataWrite": true, "weatherProvider": true } } </code><button type="button">Copy</button></pre> <h3 id="implementing-weather-handler-exports" class="tsd-anchor-link">Implementing Weather Handler Exports<a href="#implementing-weather-handler-exports" 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> Your plugin must export these handler functions: <h4 id="-get-current-weather-observations" class="tsd-anchor-link"><code>weather_get_observations</code> - Get current weather observations<a href="#-get-current-weather-observations" 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></h4> <pre><code class="typescript">export function weather_get_observations(requestJson: string): string { // requestJson: {"position": {"latitude": 60.17, "longitude": 24.94}, "options": {...}} return ( '[{"date":"2025-01-01T00:00:00Z","type":"observation","description":"Clear sky",' + '"outside":{"temperature":280.15,"relativeHumidity":0.65,"pressure":101300,"cloudCover":0.1},' + '"wind":{"speedTrue":5.0,"directionTrue":1.57}}]' ) } </code><button type="button">Copy</button></pre> <h4 id="-get-weather-forecasts" class="tsd-anchor-link"><code>weather_get_forecasts</code> - Get weather forecasts<a href="#-get-weather-forecasts" 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></h4> <pre><code class="typescript">export function weather_get_forecasts(requestJson: string): string { // requestJson: {"position": {...}, "type": "daily"|"point", "options": {"maxCount": 7}} return '[{"date":"...","type":"daily","outside":{...},"wind":{...}}]' } </code><button type="button">Copy</button></pre> <h4 id="-get-weather-warningsalerts" class="tsd-anchor-link"><code>weather_get_warnings</code> - Get weather warnings/alerts<a href="#-get-weather-warningsalerts" 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></h4> <pre><code class="typescript">export function weather_get_warnings(requestJson: string): string { // requestJson: {"position": {...}} return '[]' } </code><button type="button">Copy</button></pre> <h3 id="weather-data-format" class="tsd-anchor-link">Weather Data Format<a href="#weather-data-format" 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> <h4 id="observationforecast-object" class="tsd-anchor-link">Observation/Forecast Object<a href="#observationforecast-object" 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></h4> <pre><code class="json">{ "date": "2025-12-05T10:00:00.000Z", "type": "observation", "description": "light rain", "outside": { "temperature": 275.15, "minTemperature": 273.0, "maxTemperature": 278.0, "feelsLikeTemperature": 272.0, "relativeHumidity": 0.85, "pressure": 101300, "cloudCover": 0.75 }, "wind": { "speedTrue": 5.2, "directionTrue": 3.14, "gust": 8.0 } } </code><button type="button">Copy</button></pre> Units: <ul> <li>Temperature: Kelvin</li> <li>Humidity: Ratio (0-1)</li> <li>Pressure: Pascals</li> <li>Wind speed: m/s</li> <li>Wind direction: Radians</li> </ul> <h4 id="warning-object" class="tsd-anchor-link">Warning Object<a href="#warning-object" 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></h4> <pre><code class="json">{ "startTime": "2025-12-05T10:00:00.000Z", "endTime": "2025-12-05T18:00:00.000Z", "details": "Strong wind warning", "source": "Weather Service", "type": "Warning" } </code><button type="button">Copy</button></pre> <h3 id="accessing-weather-data-via-http" class="tsd-anchor-link">Accessing Weather Data via HTTP<a href="#accessing-weather-data-via-http" 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> <pre><code class="bash"># List providers curl http://localhost:3000/signalk/v2/api/weather/_providers # Get observations for a location curl "http://localhost:3000/signalk/v2/api/weather/observations?lat=60.17&lon=24.94" # Get daily forecasts curl "http://localhost:3000/signalk/v2/api/weather/forecasts/daily?lat=60.17&lon=24.94" # Get point-in-time forecasts curl "http://localhost:3000/signalk/v2/api/weather/forecasts/point?lat=60.17&lon=24.94" # Get weather warnings curl "http://localhost:3000/signalk/v2/api/weather/warnings?lat=60.17&lon=24.94" </code><button type="button">Copy</button></pre> <h2 id="radar-providers" class="tsd-anchor-link">Radar Providers<a href="#radar-providers" 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> WASM plugins can act as radar providers for Signal K's Radar API at <code>/signalk/v2/api/vessels/self/radars</code>. <h3 id="enabling-radar-provider-capability" class="tsd-anchor-link">Enabling Radar Provider Capability<a href="#enabling-radar-provider-capability" 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> <pre><code class="json">{ "signalk": { "wasmCapabilities": { "radarProvider": true, "network": true } } } </code><button type="button">Copy</button></pre> <h3 id="registering-as-a-radar-provider" class="tsd-anchor-link">Registering as a Radar Provider<a href="#registering-as-a-radar-provider" 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> <pre><code class="typescript">// Declare the host function @external("env", "sk_register_radar_provider") declare function sk_register_radar_provider(namePtr: usize, nameLen: i32): i32; export function start(configJson: string): i32 { const name = "My Radar Plugin"; const nameBytes = String.UTF8.encode(name); const result = sk_register_radar_provider( changetype<usize>(nameBytes), nameBytes.byteLength ); if (result === 0) { sk_set_plugin_error("Failed to register as radar provider", 38); return 1; } return 0; } </code><button type="button">Copy</button></pre> <h3 id="required-handler-exports" class="tsd-anchor-link">Required Handler Exports<a href="#required-handler-exports" 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> <pre><code class="typescript">// Return JSON array of radar IDs this provider manages export function radar_get_radars(): string { return JSON.stringify(['radar-0', 'radar-1']) } // Return RadarInfo JSON for a specific radar export function radar_get_radar_info(requestJson: string): string { const info = { id: 'radar-0', name: 'Furuno DRS4D-NXT', brand: 'Furuno', status: 'transmit', spokesPerRevolution: 2048, maxSpokeLen: 1024, range: 2000, controls: { gain: { auto: false, value: 50 }, sea: { auto: true, value: 30 } } } return JSON.stringify(info) } </code><button type="button">Copy</button></pre> <h3 id="radarinfo-interface" class="tsd-anchor-link">RadarInfo Interface<a href="#radarinfo-interface" 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> <pre><code class="typescript">interface RadarInfo { id: string // Unique radar ID name: string // Display name brand?: string // Manufacturer status: 'off' | 'standby' | 'transmit' | 'warming' spokesPerRevolution: number // Spokes per rotation maxSpokeLen: number // Max spoke samples range: number // Current range (meters) controls: RadarControls // Current control values legend?: LegendEntry[] // Color legend for display streamUrl?: string // Optional external WebSocket URL } </code><button type="button">Copy</button></pre> <h3 id="streaming-radar-spokes" class="tsd-anchor-link">Streaming Radar Spokes<a href="#streaming-radar-spokes" 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> Radar spoke data arrives at ~60Hz (2048 spokes/rotation × 30-60 RPM). Plugins stream binary protobuf data directly to clients: <pre><code class="typescript">import { sk_radar_emit_spokes } from './signalk-