1.3.6 Basic Server Output

In a similar style to input-related PDUs (as specified in section 1.3.5), server output-related PDUs come in two types: slow-path and fast-path. Slow-path output is similar to T.128 output and is not optimized in any way. Fast-path output uses reduced or removed headers to save bandwidth and reduce encoding and decoding latency by reducing the required CPU cycles.

The most fundamental output that a server can send to a connected client is bitmap images of the user's session using Bitmap Updates. This allows the client to render the working space and enables a user to interact with the session running on the server. The global palette information for a session is sent to the client using Palette Updates.

The client can choose to render the mouse cursor locally (if it is not included in the graphics updates sent by the server). In this case, the server sends updates of the current cursor image to ensure that it can be drawn with the correct shape (the Pointer Update PDUs are used to accomplish this task). Furthermore, if the mouse is programmatically moved in the user's session, the server informs the client of the new position using the Pointer Position PDU.

Other basic output which a server sends to a connected client includes the Play Sound PDU, which instructs a client to play rudimentary sounds (by specifying a frequency and its duration) and Connection Management PDUs, as specified in section 2.2.10.