3.2.5.1 Sending Outgoing Messages

Messages are constructed according to Remote Desktop Protocol: File System Virtual Channel Extension as a device I/O control message on the redirected device dwDeviceId. The call packet MUST follow the format specified in IOCTL Processing Rules. The structure MUST be encoded as specified in [MS-RPCE] section 2. The output buffer length SHOULD be set to 2,048 bytes.

The message is sent to the protocol server by using a transport as specified in [MS-RDPEFS] section 2.1.