You can change the setting.

  1. Shut down the server. Make sure all clients have disconnected
  2. Go to the folder containing the server executable (e.g. C:\Program Files (x86)\QSAR Toolbox\QSAR Toolbox 4.5\Toolbox Server\Bin) 
  3. Open ToolboxServerApp.dll.config file using Notepad. 
  4. Search for "SingleUser" and you will find the line "<add key="SingleUser" value="false"></add>". 
  5. Change the value from false to true. It should look like this: <add key="SingleUser" value="true"></add>
  6. Make sure none of the remote clients will attempt to connect to the server, start the server and connect to it with the local client.