--- a/Toolbox/SingleApplication.py	Wed Jun 28 20:05:15 2017 +0200
+++ b/Toolbox/SingleApplication.py	Thu Jun 29 18:51:03 2017 +0200
@@ -9,6 +9,7 @@
 
 from __future__ import unicode_literals
 
+from PyQt5.QtCore import QByteArray
 from PyQt5.QtNetwork import QLocalServer, QLocalSocket
 
 
@@ -162,7 +163,7 @@
         @param cmd command to be sent (string)
         """
         if self.connected:
-            self.sock.write(cmd)
+            self.sock.write(QByteArray(cmd.encode()))
             self.sock.flush()
         
     def errstr(self):