graceful handling of disconnects and page reloads

src/client.js

@@ -1,6 +1,106 @@
 const vid = document.querySelector('video');
 const wsProto = window.location.protocol === 'https:' ? 'wss' : 'ws';
-const socket = new WebSocket(`${wsProto}://${window.location.hostname}:${window.location.port}`);
+let socket = null; // Initialize socket as null
+let retryInterval = 1000; // Initial retry interval in milliseconds
+const maxRetryInterval = 30000; // Maximum retry interval
+
+function createWebSocket() {
+	socket = new WebSocket(`${wsProto}://${window.location.hostname}:${window.location.port}`);
+
+	// Connection opened
+	socket.addEventListener('open', function (event) {
+		console.log('Connected to WS Server');
+		retryInterval = 1000; // Reset retry interval on successful connection
+	});
+
+	// Got message from the server
+	socket.addEventListener("message", (event) => {
+
+		// Reload the page if the server sends a reload request
+		if (event.data.startsWith("reload_request")) {
+			console.log("Reloading the page as requested by the server");
+			setTimeout(() => window.location.reload(), 1000);
+			return;
+		}
+
+		// Time syncing backward server-response
+		if (event.data.startsWith("time_sync_response_backward")) {
+			let time_at_server = Number(event.data.slice("time_sync_response_backward".length + 1));
+			let under_estimate_latest = time_at_server - get_global_time(0);
+
+			under_estimates.push(under_estimate_latest);
+			under_estimate = median(under_estimates);
+			correction = (under_estimate + over_estimate) / 2;
+
+			console.log(`%c Updated val for under_estimate is ${under_estimate}`, "color:green");
+			console.log(`%c New correction time is ${correction} miliseconds`, 'color:red; font-size:12px');
+		}
+		
+		// Time syncing forward server-response
+		if (event.data.startsWith("time_sync_response_forward")) {
+			let calculated_diff = Number(event.data.slice("time_sync_response_forward".length + 1));
+			over_estimates.push(calculated_diff);
+			over_estimate = median(over_estimates);
+			correction = (under_estimate + over_estimate) / 2;
+
+			console.log(`%c Updated val for over_estimate is ${over_estimate}`, "color:green");
+			console.log(`%c New correction time is ${correction} miliseconds`, 'color:red; font-size:12px');
+		}
+
+		// Video state update from server
+		if (event.data.startsWith("state_update_from_server")) {
+			let state = JSON.parse(event.data.slice("state_update_from_server".length + 1));
+
+			// Whenever the client connects or reconnects
+			if (client_uid == null) {
+				client_uid = state.client_uid;
+			}
+
+			// calculating the new timestamp for both cases - when the video is playing and when it is paused
+			let proposed_time = (state.playing) ? ((get_global_time(correction) - state.global_timestamp) / 1000 + state.video_timestamp) : (state.video_timestamp);
+			let gap = Math.abs(proposed_time - vid.currentTime);
+
+			console.log(`%cGap was ${proposed_time - vid.currentTime}`, 'font-size:12px; color:purple');
+			if (state.playing) {
+				// tolerance while the video is playing
+				if (gap > PLAYING_THRESH) {
+					vid.currentTime = proposed_time;
+				}
+				vid.play()
+			} else {
+				vid.pause()
+				// condition to prevent an unnecessary seek
+				if (gap > PAUSED_THRESH) {
+					vid.currentTime = proposed_time;
+				}
+			}
+		}
+	});
+
+	// Connection closed
+	socket.addEventListener('close', function (event) {
+		console.log('Disconnected from the WS Server');
+		client_uid = null;
+		retryWebSocketConnection(); // Attempt to reconnect
+	});
+
+	// Connection error
+	socket.addEventListener('error', function (event) {
+		console.error('WebSocket error:', event);
+		socket.close(); // Ensure the socket is closed on error
+	});
+}
+
+function retryWebSocketConnection() {
+	console.log(`Attempting to reconnect in ${retryInterval / 1000} seconds...`);
+	setTimeout(() => {
+		retryInterval = Math.min(retryInterval * 2, maxRetryInterval); // Exponential backoff
+		createWebSocket(); // Recreate the WebSocket connection
+	}, retryInterval);
+}
+
+// Initial WebSocket connection
+createWebSocket();
 
 // if the new tms is within this margin of the current tms, then the change is ignored for smoother viewing
 const PLAYING_THRESH = 1;
@@ -19,78 +119,6 @@ let over_estimate = 0;
 let under_estimate = 0;
 let correction = 0;
 
-
-// Connection opened
-socket.addEventListener('open', function (event) {
-	console.log('Connected to WS Server');
-});
-
-// Got message from the server
-socket.addEventListener("message", (event) => {
-
-	// Time syncing backward server-response
-	if (event.data.startsWith("time_sync_response_backward")) {
-		let time_at_server = Number(event.data.slice("time_sync_response_backward".length + 1));
-		let under_estimate_latest = time_at_server - get_global_time(0);
-
-		under_estimates.push(under_estimate_latest);
-		under_estimate = median(under_estimates);
-		correction = (under_estimate + over_estimate) / 2;
-
-		console.log(`%c Updated val for under_estimate is ${under_estimate}`, "color:green");
-		console.log(`%c New correction time is ${correction} miliseconds`, 'color:red; font-size:12px');
-	}
-	
-	// Time syncing forward server-response
-	if (event.data.startsWith("time_sync_response_forward")) {
-		let calculated_diff = Number(event.data.slice("time_sync_response_forward".length + 1));
-		over_estimates.push(calculated_diff);
-		over_estimate = median(over_estimates);
-		correction = (under_estimate + over_estimate) / 2;
-
-		console.log(`%c Updated val for over_estimate is ${over_estimate}`, "color:green");
-		console.log(`%c New correction time is ${correction} miliseconds`, 'color:red; font-size:12px');
-	}
-
-	// Video state update from server
-	if (event.data.startsWith("state_update_from_server")) {
-		let state = JSON.parse(event.data.slice("state_update_from_server".length + 1));
-
-		// Whenever the client connects or reconnects
-		if (client_uid == null) {
-			client_uid = state.client_uid;
-		}
-
-		// calculating the new timestamp for both cases - when the video is playing and when it is paused
-		let proposed_time = (state.playing) ? ((get_global_time(correction) - state.global_timestamp) / 1000 + state.video_timestamp) : (state.video_timestamp);
-		let gap = Math.abs(proposed_time - vid.currentTime);
-
-		console.log(`%cGap was ${proposed_time - vid.currentTime}`, 'font-size:12px; color:purple');
-		if (state.playing) {
-			// tolerance while the video is playing
-			if (gap > PLAYING_THRESH) {
-				vid.currentTime = proposed_time;
-			}
-			vid.play()
-		} else {
-			vid.pause()
-			// condition to prevent an unnecessary seek
-			if (gap > PAUSED_THRESH) {
-				vid.currentTime = proposed_time;
-			}
-		}
-	}
-});
-
-
-// Connection closed
-socket.addEventListener('close', function (event) {
-	console.log('Disconnected from the WS Server');
-	client_uid = null;
-	setTimeout(() => window.location.reload(), 1000);
-});
-
-
 // Send video state update to the server
 // event: the video event (ex: seeking, pause play) 
 function state_change_handler(event) {
@@ -111,7 +139,9 @@ function state_change_handler(event) {
 		client_uid: client_uid
 	};
 
-	socket.send(`state_update_from_client ${JSON.stringify(state_image)}`);
+	if (socket.readyState === WebSocket.OPEN) {
+		socket.send(`state_update_from_client ${JSON.stringify(state_image)}`);
+	}
 }
 
 // assigning event handlers
@@ -213,3 +243,4 @@ document.addEventListener('DOMContentLoaded', function() {
 		style.textContent = `::cue { font-size: ${size} !important; }`;
 	});
 });
+

src/index.js

@@ -187,7 +187,10 @@ server.listen(settings.server_port, settings.server_ip,
 process.on('SIGINT', () => {
 	console.log("Shutting down server...");
 	// wss.close();
-	wss.clients.forEach(client => client.terminate());
+	wss.clients.forEach(client => {
+		client.send("reload_request");
+		client.terminate();
+	});
 	server.close(() => {
 		console.log("Server closed");
 		process.exit(0);