[Config] Make the listen address configurable via BIND_ADDRESS

README.md

@@ -19,6 +19,7 @@ Live web UI for `events.log` and `openhab.log` built with Node.js, Express, and
 | Variable | Default | Description |
 | --- | --- | --- |
 | `PORT` | `9001` | HTTP port used by the application |
+| `BIND_ADDRESS` | `0.0.0.0` | Network interface address the server listens on. Set to `127.0.0.1` to restrict access to the local host, e.g. when a reverse proxy runs on the same machine. An unbindable address (typo, address not present on this host) makes startup fail loudly instead of binding somewhere unexpected. |
 | `OPENHAB_LOG_DIR` | `/var/log/openhab` | Fallback directory for log files |
 | `EVENTS_LOG_PATH` | `/var/log/openhab/events.log` | Full path to `events.log` |
 | `OPENHAB_LOG_PATH` | `/var/log/openhab/openhab.log` | Full path to `openhab.log` |

deploy/systemd/openhab-log-viewer.service

@@ -20,6 +20,8 @@ Environment=CLIENT_MAX_RENDERED_LINES=500
 # Uncomment to reject requests whose Host header is not on the allowlist
 # (DNS-rebinding mitigation). Comma-separated, no port; use bracketed IPv6:
 # Environment=ALLOWED_HOSTS=openhab-pi,192.168.1.10
+# Uncomment to restrict the listener, e.g. when a reverse proxy runs on this host:
+# Environment=BIND_ADDRESS=127.0.0.1
 EnvironmentFile=-/etc/default/openhab-log-viewer
 ExecStart=/usr/bin/node dist/server/index.cjs
 Restart=always

src/server/config.test.ts

@@ -7,6 +7,7 @@ import { loadConfig } from './config.js';
 
 const CONFIG_ENV_KEYS = [
   'PORT',
+  'BIND_ADDRESS',
   'INITIAL_LINES_PER_FILE',
   'MAX_BUFFERED_LINES',
   'CLIENT_MAX_RENDERED_LINES',
@@ -45,6 +46,7 @@ describe('loadConfig defaults', () => {
   it('uses documented defaults when no env vars are set', () => {
     const config = loadConfig();
     assert.equal(config.port, 9001);
+    assert.equal(config.bindAddress, '0.0.0.0');
     assert.equal(config.initialLinesPerFile, 500);
     assert.equal(config.maxBufferedLines, 2000);
     assert.equal(config.clientMaxRenderedLines, 500);
@@ -143,6 +145,22 @@ describe('loadConfig health details parsing', () => {
   });
 });
 
+describe('loadConfig bind address parsing', () => {
+  it('defaults to 0.0.0.0 when unset', () => {
+    assert.equal(loadConfig().bindAddress, '0.0.0.0');
+  });
+
+  it('uses the configured address', () => {
+    process.env.BIND_ADDRESS = '127.0.0.1';
+    assert.equal(loadConfig().bindAddress, '127.0.0.1');
+  });
+
+  it('treats a whitespace-only value as unset', () => {
+    process.env.BIND_ADDRESS = '   ';
+    assert.equal(loadConfig().bindAddress, '0.0.0.0');
+  });
+});
+
 describe('loadConfig allowed hosts parsing', () => {
   it('defaults to an empty list', () => {
     assert.deepEqual(loadConfig().allowedHosts, []);

src/server/config.ts

@@ -117,6 +117,10 @@ export function loadConfig(): AppConfig {
 
   return {
     port: clampInteger('PORT', 9001, 1, 65_535),
+    // Default '0.0.0.0' preserves current behavior (bind all interfaces). No
+    // further validation: an unbindable address fails loudly at listen() time
+    // (see the server's 'error' handler), so any string is passed through.
+    bindAddress: process.env.BIND_ADDRESS?.trim() || '0.0.0.0',
     initialLinesPerFile: clampInteger('INITIAL_LINES_PER_FILE', 500, 1, 100_000),
     maxBufferedLines: clampInteger('MAX_BUFFERED_LINES', 2_000, 100, 1_000_000),
     // The browser hard-caps rendering at CLIENT_MAX_RENDERED_LINES_CAP (500) for

src/server/index.ts

@@ -79,8 +79,13 @@ async function main(): Promise<void> {
   app.use(htmlLimiter);
   app.use(createSpaFallback(clientDistDir));
 
-  const server = app.listen(config.port, () => {
-    console.log(`OpenHab Log Viewer listening on port ${config.port}`);
+  const server = app.listen(config.port, config.bindAddress, () => {
+    console.log(`OpenHab Log Viewer listening on ${config.bindAddress}:${config.port}`);
+  });
+
+  server.on('error', (error) => {
+    console.error('[startup] Failed to bind server:', error);
+    process.exit(1);
   });
 
   const shutdown = createShutdown({ tailers, sseHub, server });

src/server/routes.test.ts

@@ -13,6 +13,7 @@ const NO_HEARTBEAT = 1_000_000_000;
 function baseConfig(overrides: Partial<AppConfig> = {}): AppConfig {
   return {
     port: 9001,
+    bindAddress: '0.0.0.0',
     initialLinesPerFile: 500,
     maxBufferedLines: 2000,
     clientMaxRenderedLines: 500,

src/server/types.ts

@@ -12,6 +12,7 @@ export interface SourceConfig {
 
 export interface AppConfig {
   port: number;
+  bindAddress: string;
   initialLinesPerFile: number;
   maxBufferedLines: number;
   clientMaxRenderedLines: number;