Resolve dns according the selected ip version before connecting to ho…

…st (see HorizenOfficial#25)

Otherwise the ipv4 address is resolved.

Removed "{ multiplex: false }" option since it's the same as "{ forceNew : true }" according docs (https://socket.io/docs/client-api/#new-manager-url-options)
"[...] unless the multiplex option is passed with false. Passing this option is the equivalent of passing 'force new connection': true or forceNew: true."

app.js

@@ -1,6 +1,7 @@
 const SecNode = require('./SecNodeTracker').auto();
 const LocalStorage = require('node-localstorage').LocalStorage;
 const local = new LocalStorage('./config');
+const dns = require('dns');
 const io = require('socket.io-client')
 const os = require('os');
 const pkg = require('./package.json');
@@ -15,12 +16,14 @@ if (local.length == 0) {
 // host names without domain
 const servers = local.getItem('servers').split(',');
 const home = local.getItem('home');
+const ipv = local.getItem('ipv');
 if (!home) return console.log("ERROR SETTING THE HOME SERVER. Please try running setup again or report the issue.")
 let curIdx = servers.indexOf(home);
 let curServer = home;
 const protocol = `${init.protocol}://`;
 let domain = `.${init.domain}`;
-let socket = io(protocol + curServer + domain, { multiplex: false });
+
+let socket;
 let failoverTimer;
 
 //get cpu config
@@ -55,6 +58,15 @@ ident.con = { home: home, cur: curServer }
 let initTimer;
 let returningHome = false;
 
+function openSocket(afterCreation) {
+	dns.lookup(curServer + domain, {family: ipv}, (err, address, family) => {
+		console.log("Using " + address + " for tracker communication");
+		socket = io(protocol + address, { forceNew : true })
+		setSocketEvents();
+		afterCreation();
+	});
+}
+
 const initialize = () => {
 	// check connectivity by getting the t_address.
 	// pass identity to server on success
@@ -106,7 +118,7 @@ const initialize = () => {
 				SecNode.getNetworks(null, (err, nets) => {
 					ident.nets = nets;
 					socket.emit('initnode', ident, () => {
-						//only pass email and nets on init.  
+						//only pass email and nets on init.
 						delete ident.email;
 						delete ident.nets;
 					});
@@ -140,11 +152,11 @@ const setSocketEvents = () => {
 		returningHome = true;
 		console.log(logtime(), `Returning to home server ${curServer}.`);
 		socket.close();
-		socket = io(protocol + curServer + domain, { forceNew: true });
-		setSocketEvents();
-		SecNode.socket = socket;
-		ident.con.cur = curServer;
-		returningHome = false;
+		openSocket(() => {
+			SecNode.socket = socket;
+			ident.con.cur = curServer;
+			returningHome = false;
+		});
 	})
 
 	socket.on('msg', (msg) => {
@@ -182,14 +194,13 @@ const setSocketEvents = () => {
 			case 'networks':
 				SecNode.getNets(data);
 				break;
-				
+
 			case 'changeServer':
 				switchServer(data.server);
 				break;
 		}
 	})
 }
-setSocketEvents();
 
 const logtime = () => {
 	return (new Date()).toISOString().replace(/T/, ' ').replace(/\..+/, '') + " GMT" + " --";
@@ -206,10 +217,10 @@ const switchServer = (server) => {
 	curIdx = nextIdx;
 	console.log(logtime(), "Trying server: " + curServer);
 	socket.close();
-	socket = io.connect(protocol + curServer + domain);
-	setSocketEvents();
-	SecNode.socket = socket;
-	ident.con.cur = curServer;
+	openSocket(() => {
+		SecNode.socket = socket;
+		ident.con.cur = curServer;
+	});
 }
 
 
@@ -227,7 +238,8 @@ const conCheck = () => {
 	)
 }
 
-SecNode.socket = socket;
-SecNode.initialize();
-conCheck();
-
+openSocket(() => {
+	SecNode.socket = socket;
+	SecNode.initialize();
+	conCheck();
+});