host: handle a second client connecting later

We don't have a way to unregister from events, so, check if _isConnected

src/host.js

@@ -56,6 +56,10 @@ Host.prototype.connect = function connect() {
 	var me = this;
 	return new Promise(function(resolve/*, reject*/) {
 		me.onEvent('ready', function() {
+			if (me._isConnected) {
+				return;
+			}
+
 			resolve(Port.prototype.connect.call(me));
 		});
 		me.open();