Re: Keyboard scan codes

[Guy Harris <guy () alum mit edu>]

On Apr 16, 2012, at 10:52 AM, Kaul wrote:

> I was wondering if there is somewhere in Wireshark code definition for keyboard scan codes. I was hoping to re-use if 
> such exists. I'm looking for 101/102 AT keyboard scan codes, specifically (was hoping RDP or VNC would have them, but 
> did not find it,

For VNC, this is not surprising - as the VNC spec:

        http://www.realvnc.com/docs/rfbproto.pdf

says, VNC sends X11 keysyms, not raw keyboard scan codes, over the wire.

At least as I read the RDP spec - section 2.2.8.1.1.3.1.1.1 "Keyboard Event (TS_KEYBOARD_EVENT)" of "[MS-RDPBCGR]: 
Remote Desktop Protocol: Basic Connectivity and Graphics Remoting Specification" - those *do* contain scan codes:

        The TS_KEYBOARD_EVENT structure is a standard T.128 Keyboard Event (see [T128] section 8.18.2). RDP keyboard 
input is restricted to keyboard scancodes, unlike the code-point or virtual codes supported in T.128 (a scancode is an 
8-bit value specifying a key location on the keyboard). The server accepts a scancode value and translates it into the 
correct character depending on the language locale and keyboard layout used in the session.

but the RDP dissector doesn't appear to parse input events, so it has no table for PC keyboard scan codes.

> neither did Telnet).

Again, not surprising - as the TELNET specification, RFC 854:

        http://tools.ietf.org/html/rfc854

says:

        The NVT printer has an unspecified carriage width and page length and can produce representations of all 95 
USASCII graphics (codes 32 through 126).

so it uses ASCII, not raw scan codes (not surprising, given that TELNET's predecessors:

        http://tools.ietf.org/html/rfc15

long antedate the IBM Personal Computer).

> I don't think what X11 uses would suite me.

No, X11's "keycodes" are not guaranteed to be PC keyboard scan codes (as X11 servers are not guaranteed to be PCs), and 
are only interpretable with a keycode-to-keysym table from the server, and the keysyms are keyboard-independent and are 
ASCII-based.
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