diff --git a/common/util.cpp b/common/util.cpp
index 3d73cc3..707dfe7 100644
--- a/common/util.cpp
+++ b/common/util.cpp
@@ -23,11 +23,14 @@ void Util::processOutput(QString output)
 void Util::execCMD(QString cmd)
 {
     qDebug() << cmd;
-    emit write(cmd + "\r\n");
+    if(isRunning)
+        emit write(cmd + "\r\n");
 }
 
 QString Util::execCMDWithOutput(QString cmd, unsigned long waitTime)
 {
+    if(!isRunning)
+        return "";
     QTime currTime = QTime::currentTime();
     QTime targetTime = QTime::currentTime().addMSecs(waitTime);
     isRequiringOutput = true;
@@ -61,3 +64,8 @@ void Util::setClientType(Util::ClientType clientType)
 {
     this->clientType = clientType;
 }
+
+void Util::setRunningState(bool st)
+{
+    this->isRunning = st;
+}
diff --git a/common/util.h b/common/util.h
index adc9291..b2ca006 100644
--- a/common/util.h
+++ b/common/util.h
@@ -31,9 +31,11 @@ public:
 public slots:
     void processOutput(QString output);
     void setClientType(Util::ClientType clientType);
+    void setRunningState(bool st);
 
 private:
     bool isRequiringOutput;
+    bool isRunning;
     QString* requiredOutput;
     QTime timeStamp;
     ClientType clientType;
diff --git a/ui/mainwindow.cpp b/ui/mainwindow.cpp
index 2b30c0f..8fbbd8a 100644
--- a/ui/mainwindow.cpp
+++ b/ui/mainwindow.cpp
@@ -875,6 +875,7 @@ void MainWindow::signalInit()
 
     connect(this, &MainWindow::connectPM3, pm3, &PM3Process::connectPM3);
     connect(pm3, &PM3Process::PM3StatedChanged, this, &MainWindow::onPM3StateChanged);
+    connect(pm3, &PM3Process::PM3StatedChanged, util, &Util::setRunningState);
     connect(this, &MainWindow::killPM3, pm3, &PM3Process::kill);
 
     connect(util, &Util::write, pm3, &PM3Process::write);