server: add websocket ping mechanism

fixes FoundKeyGang/FoundKey#336

Changelog: Fixed

packages/backend/src/server/api/streaming.ts

@@ -2,7 +2,7 @@ import { EventEmitter } from 'events';
 import * as http from 'node:http';
 import { WebSocketServer } from 'ws';
 
-import { MINUTE } from '@/const.js';
+import { SECOND, MINUTE } from '@/const.js';
 import { subscriber as redisClient } from '@/db/redis.js';
 import { Users } from '@/models/index.js';
 import { Connection } from './stream/index.js';
@@ -43,6 +43,20 @@ export const initializeStreamingServer = (server: http.Server): void => {
 
 			const main = new Connection(socket, ev, user, app);
 
+			// ping/pong mechanism
+			let pingTimeout = null;
+			function startHeartbeat() {
+				if (pingTimeout) clearTimeout(pingTimeout);
+
+				socket.ping();
+				pingTimeout = setTimeout(() => {
+					socket.terminate();
+				}, 30 * SECOND);
+			}
+			startHeartbeat();
+			socket.on('ping', () => { startHeartbeat(); });
+			socket.on('pong', () => { startHeartbeat(); });
+
 			// keep user "online" while a stream is connected
 			const intervalId = user ? setInterval(() => {
 				Users.update(user.id, {
@@ -54,11 +68,13 @@ export const initializeStreamingServer = (server: http.Server): void => {
 					lastActiveDate: new Date(),
 				});
 			}
+
 			socket.once('close', () => {
 				ev.removeAllListeners();
 				main.dispose();
 				redisClient.off('message', onRedisMessage);
 				if (intervalId) clearInterval(intervalId);
+				if (pingTimeout) clearTimeout(pingTimeout);
 			});
 
 			// ping/pong mechanism