fix: check socket state

application/source/data/datasource/websocket.mjs

@@ -231,14 +231,15 @@ class WebSocketDatasource extends Datasource {
 
     /**
      * @return {Promise}
-     * @throws {Error} the options does not contain a valid json definition
-     * @throws {Error} the data cannot be read
-     * @throws {TypeError} value is not an object
      */
     read() {
         const self = this;
         let response;
 
+        if (self[connectionSymbol].socket||self[connectionSymbol].socket.readyState!==1) {
+            return Promise.reject('The connection is not established.');
+        }        
+
         return new Promise((resolve, reject) => {
             if (self[receiveQueueSymbol].isEmpty()) {
                 resolve();
@@ -291,6 +292,10 @@ class WebSocketDatasource extends Datasource {
     write() {
         const self = this;
         
+        if (self[connectionSymbol].socket||self[connectionSymbol].socket.readyState!==1) {
+            return Promise.reject('The connection is not established.');
+        }
+
         let obj = self.get();
         let transformation = self.getOption('write.mapping.transformer');
         if (transformation !== undefined) {