signalk-server

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

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aria-current="page">HTTP Endpoints</a></li></ul></div><div class="tsd-panel tsd-typography"><h1 id="http-endpoints" class="tsd-anchor-link">HTTP Endpoints<a href="#http-endpoints" 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> WASM plugins can register custom HTTP endpoints to provide REST APIs or serve dynamic content. This is useful for: <ul> <li>Providing plugin-specific APIs</li> <li>Implementing webhook receivers</li> <li>Creating custom data queries</li> <li>Building interactive dashboards</li> </ul> <h2 id="registering-http-endpoints" class="tsd-anchor-link">Registering HTTP Endpoints<a href="#registering-http-endpoints" 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> Export an <code>http_endpoints()</code> function that returns a JSON array of endpoint definitions: <pre><code class="typescript">// assembly/index.ts export function http_endpoints(): string { return `[ { "method": "GET", "path": "/api/data", "handler": "handle_get_data" }, { "method": "POST", "path": "/api/update", "handler": "handle_post_update" } ]` } </code><button type="button">Copy</button></pre> <h2 id="implementing-http-handlers" class="tsd-anchor-link">Implementing HTTP Handlers<a href="#implementing-http-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></h2> Handler functions receive a request context and return an HTTP response: <pre><code class="typescript">export function handle_get_data(requestPtr: usize, requestLen: usize): string { // 1. Decode request from WASM memory const requestBytes = new Uint8Array(i32(requestLen)) for (let i: i32 = 0; i < i32(requestLen); i++) { requestBytes[i] = load<u8>(requestPtr + <usize>i) } const requestJson = String.UTF8.decode(requestBytes.buffer) // 2. Parse request (contains method, path, query, params, body, headers) // Simple example: extract query parameter let filter = '' const filterIndex = requestJson.indexOf('"filter"') if (filterIndex >= 0) { // Extract the filter value from JSON // (In production, use proper JSON parsing) } // 3. Process request and build response data const data = { items: [ { id: 1, value: 'Item 1' }, { id: 2, value: 'Item 2' } ], count: 2 } const bodyJson = JSON.stringify(data) // 4. Escape JSON for embedding in response string const escapedBody = bodyJson .replaceAll('"', '\\"') .replaceAll('\n', '\\n') .replaceAll('\r', '\\r') // 5. Return HTTP response (status, headers, body) return `{ "statusCode": 200, "headers": {"Content-Type": "application/json"}, "body": "${escapedBody}" }` } export function handle_post_update( requestPtr: usize, requestLen: usize ): string { const requestBytes = new Uint8Array(i32(requestLen)) for (let i: i32 = 0; i < i32(requestLen); i++) { requestBytes[i] = load<u8>(requestPtr + <usize>i) } const requestJson = String.UTF8.decode(requestBytes.buffer) // Process POST body and update state // ... return `{ "statusCode": 200, "headers": {"Content-Type": "application/json"}, "body": "{\\"success\\":true}" }` } </code><button type="button">Copy</button></pre> <h2 id="request-context-format" class="tsd-anchor-link">Request Context Format<a href="#request-context-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></h2> The request context is a JSON object with: <pre><code class="json">{ "method": "GET", "path": "/api/logs", "query": { "lines": "100", "filter": "error" }, "params": {}, "body": null, "headers": { "user-agent": "Mozilla/5.0...", "accept": "application/json" } } </code><button type="button">Copy</button></pre> <h2 id="response-format" class="tsd-anchor-link">Response Format<a href="#response-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></h2> Handler functions must return a JSON string with: <pre><code class="json">{ "statusCode": 200, "headers": { "Content-Type": "application/json", "Cache-Control": "no-cache" }, "body": "{\"data\": \"value\"}" } </code><button type="button">Copy</button></pre> Important Notes: <ul> <li>The <code>body</code> field must be a JSON-escaped string</li> <li>Use double escaping for quotes: <code>\\"</code> not <code>"</code></li> <li>Endpoints are mounted at <code>/plugins/your-plugin-id/api/...</code></li> <li>From browser, fetch from absolute path: <code>/plugins/your-plugin-id/api/logs</code></li> </ul> <h2 id="string-memory-management" class="tsd-anchor-link">String Memory Management<a href="#string-memory-management" 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 uses the AssemblyScript loader for automatic string handling: For plugin metadata (id, name, schema, http_endpoints): <ul> <li>Return AssemblyScript strings directly</li> <li>Server automatically decodes with <code>__getString()</code></li> </ul> For HTTP handlers: <ul> <li>Receive: <code>(requestPtr: usize, requestLen: usize)</code> - raw memory pointer</li> <li>Manually decode UTF-8 bytes from WASM memory</li> <li>Return: AssemblyScript string with escaped JSON</li> <li>Server automatically decodes with <code>__getString()</code></li> </ul> Why manual decoding for handlers? The request is passed as raw UTF-8 bytes for efficiency, but the response is returned as an AssemblyScript string (UTF-16LE) which the loader decodes automatically. <h2 id="testing-your-endpoints" class="tsd-anchor-link">Testing Your Endpoints<a href="#testing-your-endpoints" 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> <pre><code class="bash"># Test GET endpoint curl http://localhost:3000/plugins/my-plugin/api/data?filter=test # Test POST endpoint curl -X POST http://localhost:3000/plugins/my-plugin/api/update \ -H "Content-Type: application/json" \ -d '{"value": 123}' </code><button type="button">Copy</button></pre> <h2 id="security-considerations" class="tsd-anchor-link">Security Considerations<a href="#security-considerations" 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> <ul> <li>Endpoints are sandboxed - no direct file system access</li> <li>Memory is isolated - cannot access other plugins</li> <li>Validate all input from requests</li> <li>Implement authentication if handling sensitive data</li> <li>Set appropriate CORS headers if needed</li> </ul> </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="#registering-http-endpoints">Registering HTTP Endpoints</a><a href="#implementing-http-handlers">Implementing HTTP Handlers</a><a href="#request-context-format">Request Context Format</a><a href="#response-format">Response Format</a><a href="#string-memory-management">String Memory Management</a><a href="#testing-your-endpoints">Testing Your Endpoints</a><a href="#security-considerations">Security Considerations</a></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>