Implement requestMsg() for client-server-communication to receive data from the server

Change-Id: I6399679449199a3f5e75ca47348b4fd875f08142
diff --git a/dev/js/src/plugin/service.js b/dev/js/src/plugin/service.js
index a02e945..c8b42dd 100644
--- a/dev/js/src/plugin/service.js
+++ b/dev/js/src/plugin/service.js
@@ -1,5 +1,6 @@
 define(function () {
   "use strict";
+
   return {
     create : function (name, src, id) {
       return Object.create(this)._init(name, src, id);
@@ -43,6 +44,17 @@
       return e;
     },
 
+    /**
+     * Send a message to the embedded service.
+     */
+    sendMsg : function (d) {
+      let iframe = this.load();
+      iframe.contentWindow.postMessage(
+        d,
+        '*'
+      ); // TODO: Fix origin
+    },
+
     // onClose : function () {},
 
     /**