18.104.22.168.5.3 Sending System Command PDU
The System Command PDU is sent by the client when a RAIL window receives a system command by a means other than clicking it (for example, by pressing the Windows logo key+M to minimize the window, by clicking the Show Desktop button in the taskbar, or by selecting the system menu by pressing ALT+SPACE).
Note Mouse clicks in the RAIL window are forwarded to the server via the RDP core protocol. The PDU is initialized as specified in section 22.214.171.124.3.
The WindowId field SHOULD be initialized to the ID of an existing window on the server that is associated with the local RAIL window. The RAIL client SHOULD create this association during processing of the Window Information Order for new windows, as specified in section 126.96.36.199.1.2.1.