TRIVIAL NETWORK DISK PROTOCOL

* "CAPABILITIES REQUEST" is the only message type that should be broadcast. Everything else should be unicast

All fields are in network byte order (hi/lo)

FOR ALL MESSAGES
Offset	meaning


$00..$03	signature 'TNDP' (ASCII, high byte clear)
$04		1 byte version ID - current version = 1
$05..$06	2 byte xid (echoed back in response)

FOR ALL RQS
			
$07		1 byte opcode
		$00 = CAPABILITIES REQUEST
		$01 = VOLUME CATALOG REQUEST
		$02 = READ T/S REQUEST
		$03 = WRITE T/S REQUEST
		$04 = INIT VOLUME REQUEST

FOR CAPABILITIES REQUEST
No further data

FOR VOLUME CATALOG REQUEST
$08..		requested client system architecture 
		$00 = all architectures (regardless of architecture)
		$64 = C64
		$A2 = Apple 2

$09..		requested file system

		$00 = Any
		$01 = RAW / other
		$02 = Apple DOS 3.3
		$03 = PRODOS 8
		$04 = Apple CPM
		$05 = CBM DOS

$0A..$0B	Catalogue Offset 

For READ/WRITE:
	
$08..$09	2 byte track #
$0A..$0B	2 byte sector #
$0C..$0D	2 byte sector length (in bytes) 
$0E..$4B	volume name (null padded 55 bytes)
$4C		null byte (i.e. filename can be 55 bytes long, MUST be at least 1 null at the 56th byte)
FOR WRITE
$4d..		sector data

FOR INIT VOLUME
$00..$3c	volume name (up to 56 chars, null padded)
$37		null byte
$38		system architecture ID
$39		file system ID
$3A..$3B	number of tracks
$3C..$3D	sector length (in bytes) 
$3E..$3F	??


FOR ALL RESPONSES
		
$07		1 byte opcode
		$80 = CAPABILITIES REQUEST RESPONSE
		$81 = VOLUME CATALOG REQUEST RESPONSE
		$82 = READ T/S REQUEST RESPONSE
		$83 = WRITE T/S REQUEST RESPONSE
		$FF = ERROR RESPONSE

FOR CAPABILITIES RESPONSE
$07		Maximum supported protocol version
$08..$1b	19 byte application name
$1c		Null byte (so application name is null padded)
$1d		number of entries in  supported architectures/file systems list (must be >=1, since list should
		always contain at least a "any architecture, any file system" entry, even if the count is 0).

$1e.. 		list of supported architectures/file systems:
supported architecture/file systems lists:
	$00	system architecture ID
	$01..$02 number of volumes available for this combination of architecture/file system
	
list should be sorted by architecture ID (in descending order) and file system id (in descending order).
Each architecture list should end with a file system Id of $00 (any) which is the count of all volumes available for 
this architecture.

The list of supported architectures should end with an entry for architecture ID $00 (any) which should have a single 
file system ID $00 (any) which should have a count of all volumes available for all architectures on this server.

FOR VOLUME CATALOG
$08..$09	Total Catalogue Entries
$0A..$0B	Catalogue Offset (i.e. how many entries are there in the catalogue before the first entry in this response)
$0C		Number of Entries in this response (maximum of 10)

$0D.. 		the volume catalog entries.
for each entry

$00..$3c	volume name (up to 56 chars, null padded)
$37		null byte
$38		system architecture ID
$39		file system ID
$3A..$3B	number of tracks
$3C..$3D	sector length (in bytes) 
$3E..$3F	??




For READ/WRITE:
	
$04..$05	2 byte track #
$06..$07	2 byte sector #
$06..$07	2 byte sector length (in bytes) 
$0A..$49	volume name (null padded 64 bytes)

FOR READ
$4A..		sector data

FOR INIT VOLUME
$00..$3c	volume name (up to 56 chars, null padded)
$37		null byte
$38		system architecture ID
$39		file system ID
$3A..$3B	number of tracks
$3C..$3D	sector length (in bytes) 


	
FOR ERROR
	
$04..$05	Error Code
		$00 = OK
		$01 = BROADCAST NOT ALLOWED
			Capabilities Request (opcode=00) are the only message types that can be broadcast.
		$02 = UNKNOWN OPCODE
			The client sent a message with an opcode the server does not understand
		$03 = VERSION NOT SUPPORTED
			The client sent a message with an protocol version that the server does not support
		$04 = ARCHITECTURE NOT SUPPORTED
		$05 = FILE SYSTEM NOT SUPPORTED
		$06 = INVALID VOLUME NAME
		$07 = INVALID TRACK NUMBER
		$08 = INVALID SECTOR NUMBER
		$09 = INVALID SECTOR LENGTH

		$FF = INTERNAL SERVER ERROR
			The server suffered an internal error while processing the request

$06..$0b	bytes $04..$09 from original request
$0c..$4c	error message (null padded 63 bytes)
$4d 		null byte