diff --git a/mainwindow.cpp b/mainwindow.cpp
index dac8972..53bd11c 100644
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -9,9 +9,17 @@ namespace yremote {
 
 MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow)
 {
+    QString DEFAULT_ADDRESS = "10.0.0.227";
+
     ui->setupUi(this);
-    manager = new QNetworkAccessManager(this);
     setFixedSize(size());
+    ui->txt_address->setText(DEFAULT_ADDRESS);
+    mAddress = ui->txt_address->text();
+
+    // load initial data
+    sendCommand("<YAMAHA_AV cmd=\"GET\"><System>"
+                 "<Power_Control><Power>GetParam</Power></Power_Control>"
+                 "</System></YAMAHA_AV>");
 }
 
 MainWindow::~MainWindow()
@@ -19,39 +27,71 @@ MainWindow::~MainWindow()
     delete ui;
 }
 
-void MainWindow::func()
-{
-    QNetworkAccessManager *manager = new QNetworkAccessManager(this);
-    connect(manager, SIGNAL(finished(QNetworkReply*)),
-            this, SLOT(replyFinished(QNetworkReply*)));
-
-    manager->get(QNetworkRequest(QUrl("http://qt-project.org")));
-}
-
-
 void MainWindow::on_btn_onoff_clicked()
 {
-    qDebug() << "void MainWindow::on_btn_onoff_clicked()";
-    sendCommand("<YAMAHA_AV cmd=\"GET\"><Main_Zone><Input><Input_Sel>GetParam</Input_Sel></Input></Main_Zone></YAMAHA_AV>");
+    if (mPowered){
+        sendCommand("<YAMAHA_AV cmd=\"PUT\"><Main_Zone>"
+                    "<Power_Control><Power>Standby</Power></Power_Control>"
+                    "</Main_Zone></YAMAHA_AV>");
+
+    } else {
+        sendCommand("<YAMAHA_AV cmd=\"PUT\"><Main_Zone>"
+                    "<Power_Control><Power>On</Power></Power_Control>"
+                    "</Main_Zone></YAMAHA_AV>");
+    }
+    mPowered = !mPowered;
+    updateUi();
 }
 
-QString MainWindow::sendCommand(QString cmd)
+void MainWindow::sendCommand(QString cmd)
 {
-    QString res;
-
     QNetworkRequest request;
     request.setUrl("http://" + mAddress + ":80/YamahaRemoteControl/ctrl");
     request.setRawHeader("Content-Type", "text/xml; charset=UTF-8");
     request.setRawHeader("Content-Length", QByteArray::number(cmd.size()));
 
-    QNetworkReply *reply = manager->post(request, cmd.toUtf8());
+    QNetworkAccessManager *networkManager = new QNetworkAccessManager(this);
+    mReply = networkManager->post(request, cmd.toUtf8());
+    connect(networkManager, &QNetworkAccessManager::finished, this, &MainWindow::replyFinished);
+}
 
-    QEventLoop loop;
-    connect(reply, SIGNAL(finished()), &loop, SLOT(quit()));
-    loop.exec();
+void MainWindow::replyFinished()
+{
+    QString ans;
+    mReply->deleteLater();
 
-    qDebug() << reply->readAll();
-    return res;
+    if(mReply->error() == QNetworkReply::NoError) {
+        QByteArray data = mReply->readAll();
+        ans = QString(data);
+    } else {
+        qDebug() << mReply->url();
+        qDebug() << mReply->errorString();
+        return;
+    }
+
+    // check power state
+    qDebug() << ans;
+    QRegularExpression regex("<Power_Control><Power>(.*)</Power></Power_Control>");
+    QRegularExpressionMatch match = regex.match(ans);
+
+    if (match.hasMatch()) {
+        if (match.captured(1) == "On") mPowered = true;
+        else if (match.captured(1) == "Off") mPowered = false;
+    }
+
+    updateUi();
+}
+
+void MainWindow::updateUi() {
+    ui->btn_onoff->setText(mPowered ? "On" : "Off");
+    ui->dial->setEnabled(mPowered);
+    ui->lbl_volume->setEnabled(mPowered);
+    ui->btn_hdmi1->setEnabled(mPowered);
+    ui->btn_hdmi2->setEnabled(mPowered);
+    ui->btn_hdmi3->setEnabled(mPowered);
+    ui->btn_spotify->setEnabled(mPowered);
+    ui->btn_airplay->setEnabled(mPowered);
+    ui->btn_audioin->setEnabled(mPowered);
 }
 
 void MainWindow::on_txt_address_textEdited(const QString &arg1)
diff --git a/mainwindow.h b/mainwindow.h
index 22d4a64..e246284 100644
--- a/mainwindow.h
+++ b/mainwindow.h
@@ -23,15 +23,19 @@ protected:
 
 private slots:
     void on_btn_onoff_clicked();
-
+    void replyFinished();
     void on_txt_address_textEdited(const QString &arg1);
 
 private:
     Ui::MainWindow *ui;
-    QString sendCommand(QString cmd);
 
     QString mAddress;
-    QNetworkAccessManager *manager;
+    QNetworkReply *mReply;
+
+    bool mPowered = false;
+
+    void sendCommand(QString cmd);
+    void updateUi();
 };
 
 }
diff --git a/mainwindow.ui b/mainwindow.ui
index 62d0386..0a45761 100644
--- a/mainwindow.ui
+++ b/mainwindow.ui
@@ -35,7 +35,7 @@
     <item row="0" column="2">
      <widget class="QLineEdit" name="txt_address">
       <property name="text">
-       <string>10.0.0.5</string>
+       <string>10.0.0.227</string>
       </property>
       <property name="alignment">
        <set>Qt::AlignCenter</set>