diff --git a/ui/services/sensing.service.js b/ui/services/sensing.service.js
index 0992483b..2d5635e4 100644
--- a/ui/services/sensing.service.js
+++ b/ui/services/sensing.service.js
@@ -9,11 +9,25 @@
  * emit simulated frames so the UI can clearly distinguish live vs. fallback data.
  */
 
-// Derive WebSocket URL from the page origin so it works on any port.
-// The /ws/sensing endpoint is available on the same HTTP port (3000).
-const _wsProto = (typeof window !== 'undefined' && window.location.protocol === 'https:') ? 'wss:' : 'ws:';
-const _wsHost  = (typeof window !== 'undefined' && window.location.host) ? window.location.host : 'localhost:3000';
-const SENSING_WS_URL = `${_wsProto}//${_wsHost}/ws/sensing`;
+const SENSING_WS_PORT_BY_HTTP_PORT = {
+  // Docker image: HTTP UI/API on 3000, sensing stream on 3001.
+  '3000': '3001',
+  // Python sensing stack: UI on 8080, sensing stream on 8765.
+  '8080': '8765',
+};
+
+export function buildSensingWsUrl(locationLike = (typeof window !== 'undefined' ? window.location : null)) {
+  const protocol = locationLike && locationLike.protocol === 'https:' ? 'wss:' : 'ws:';
+  const host = locationLike && locationLike.host ? locationLike.host : 'localhost:3001';
+  const hostname = locationLike && locationLike.hostname ? locationLike.hostname : host.split(':')[0];
+  const port = locationLike && locationLike.port ? locationLike.port : '';
+  const wsPort = SENSING_WS_PORT_BY_HTTP_PORT[port];
+  const wsHost = wsPort ? `${hostname}:${wsPort}` : host;
+
+  return `${protocol}//${wsHost}/ws/sensing`;
+}
+
+const SENSING_WS_URL = buildSensingWsUrl();
 const RECONNECT_DELAYS = [1000, 2000, 4000, 8000, 16000];
 const MAX_RECONNECT_ATTEMPTS = 20;
 // Number of failed attempts that must occur before simulation starts.
diff --git a/ui/services/websocket.service.js b/ui/services/websocket.service.js
index 26f4a231..c27cea4f 100644
--- a/ui/services/websocket.service.js
+++ b/ui/services/websocket.service.js
@@ -136,9 +136,22 @@ export class WebSocketService {
 
   // Set up WebSocket event handlers
   setupEventHandlers(url, ws, handlers) {
-    const connection = this.connections.get(url);
+    const getConnection = (eventName) => {
+      const connection = this.connections.get(url);
+      if (!connection) {
+        this.logger.warn(`Ignoring WebSocket ${eventName} for unregistered connection`, {
+          url,
+          readyState: ws.readyState
+        });
+        return null;
+      }
+      return connection;
+    };
 
     ws.onopen = (event) => {
+      const connection = getConnection('open');
+      if (!connection) return;
+
       const connectionTime = Date.now() - connection.connectionStartTime;
       this.logger.info(`WebSocket connected successfully`, { url, connectionTime });
       
@@ -158,6 +171,9 @@ export class WebSocketService {
     };
 
     ws.onmessage = (event) => {
+      const connection = getConnection('message');
+      if (!connection) return;
+
       connection.lastActivity = Date.now();
       connection.messageCount++;
       
@@ -188,6 +204,9 @@ export class WebSocketService {
     };
 
     ws.onerror = (event) => {
+      const connection = getConnection('error');
+      if (!connection) return;
+
       connection.errorCount++;
       this.logger.error(`WebSocket error occurred`, { 
         url, 
@@ -208,6 +227,9 @@ export class WebSocketService {
     };
 
     ws.onclose = (event) => {
+      const connection = getConnection('close');
+      if (!connection) return;
+
       const { code, reason, wasClean } = event;
       this.logger.info(`WebSocket closed`, { url, code, reason, wasClean });
       
@@ -607,4 +629,4 @@ export class WebSocketService {
 }
 
 // Create singleton instance
-export const wsService = new WebSocketService();
\ No newline at end of file
+export const wsService = new WebSocketService();
diff --git a/ui/tests/test-runner.js b/ui/tests/test-runner.js
index 7d35977a..5e22111a 100644
--- a/ui/tests/test-runner.js
+++ b/ui/tests/test-runner.js
@@ -3,6 +3,7 @@
 import { API_CONFIG, buildApiUrl, buildWsUrl } from '../config/api.config.js';
 import { apiService } from '../services/api.service.js';
 import { wsService } from '../services/websocket.service.js';
+import { buildSensingWsUrl } from '../services/sensing.service.js';
 import { poseService } from '../services/pose.service.js';
 import { healthService } from '../services/health.service.js';
 import { TabManager } from '../components/TabManager.js';
@@ -232,6 +233,17 @@ testRunner.test('buildWsUrl constructs WebSocket URLs', 'apiConfig', () => {
   testRunner.assert(url.includes('token=test-token'), 'URL should contain token parameter');
 });
 
+testRunner.test('buildSensingWsUrl maps Docker UI port to sensing WebSocket port', 'apiConfig', () => {
+  const url = buildSensingWsUrl({
+    protocol: 'http:',
+    host: '192.168.28.147:3000',
+    hostname: '192.168.28.147',
+    port: '3000',
+  });
+
+  testRunner.assertEqual(url, 'ws://192.168.28.147:3001/ws/sensing');
+});
+
 // API Service Tests
 testRunner.test('apiService has required methods', 'apiService', () => {
   testRunner.assert(typeof apiService.get === 'function', 'get method should exist');
@@ -473,4 +485,4 @@ document.addEventListener('DOMContentLoaded', () => {
   testRunner.updateSummary();
 });
 
-export { testRunner };
\ No newline at end of file
+export { testRunner };