The main window is the application window of Modbus Client.
If you select Menu>New (Ctrl+N) or Menu>Open (Ctrl+O) you create a new or open an existing connection window. You can drag-n-drop a *.mbc file onto the main window if you want. All settings of the active connection window can be saved by Menu>Save (Ctrl+S).
At any time you can have multiple connections to one or more devices. It is also possible to open the same connection more than once.
See also : Connection window (analog) and Connection window (discrete)