Determine real-time HTTP connected status (#3335)

* Determine real-time HTTP connected status

* Update failing tests, no polluting polling

js/src/api/transport/http/http.js

@@ -19,11 +19,14 @@ import JsonRpcBase from '../jsonRpcBase';
 
 /* global fetch */
 export default class Http extends JsonRpcBase {
-  constructor (url) {
+  constructor (url, connectTimeout = 1000) {
     super();
 
     this._connected = true;
     this._url = url;
+    this._connectTimeout = connectTimeout;
+
+    this._pollConnection();
   }
 
   _encodeOptions (method, params) {
@@ -77,4 +80,17 @@ export default class Http extends JsonRpcBase {
         return response.result;
       });
   }
+
+  _pollConnection = () => {
+    if (this._connectTimeout <= 0) {
+      return;
+    }
+
+    const nextTimeout = () => setTimeout(this._pollConnection, this._connectTimeout);
+
+    this
+      .execute('net_listening')
+      .then(nextTimeout)
+      .catch(nextTimeout);
+  }
 }