fix for #3380, socket.io timeout closure (#3862)

socket.io times out and closes the client side socket without any
callback
sendSocntNotification() from the server side data is lost as the socket
is closed. but the client doesn't know

increase the timeout 

fixes #3380

js/server.js

@@ -42,7 +42,9 @@ function Server (config) {
 					origin: /.*$/,
 					credentials: true
 				},
-				allowEIO3: true
+				allowEIO3: true,
+				pingInterval: 120000, // server → client ping every 2 mins
+				pingTimeout: 120000 // wait up to 2 mins for client pong
 			});
 
 			server.on("connection", (socket) => {

js/socketclient.js

@@ -13,7 +13,9 @@ const MMSocket = function (moduleName) {
 		base = config.basePath;
 	}
 	this.socket = io(`/${this.moduleName}`, {
-		path: `${base}socket.io`
+		path: `${base}socket.io`,
+		pingInterval: 120000, // send pings every 2 mins
+		pingTimeout: 120000 // wait up to 2 mins for a pong
 	});
 
 	let notificationCallback = function () {};