Michael J. Mahon (pre)announced on comp.sys.apple2 that he’s finishing up a server for his NadaNet project. It sounds exciting and we’re looking forward to seeing it’s release.

I’m finishing up a file server for NadaNet that is written in Applesoft BASIC running under ProDOS, in less than 300 lines, with Applesoft client-side code of about 15 lines.  ?

It handles all the BASIC.SYSTEM commands that make sense from a remote machine (BSAVE, BLOAD, BRUN, SAVE, RUN, CREATE, DELETE, LOCK, UNLOCK, RENAME, and VERIFY), with all the legal parameters. After each command is completed by the server, it posts to the client the result code (with error code, if any), the AUX TYPE, and the EOF of the file if data was transferred.

This allows any machine on a NadaNet to use the filesystem on the server using an invoking interface like:

RQ$ = “bload myprog,a$2000”:gosub 10000
Of course, the request string can be formed by concatenating any variable parameter values, etc., as desired.

Errors can be handled in-line by setting EH=1 prior to the GOSUB and then examining the value of RC after the GOSUB.  (If EH=0, then any error results in an error message and a STOP.)

The current implementation is geared to a network of more than two machines, and uses a message server to queue the requests.  The server and client code are easily modified for a two-machine network that forgoes queueing (since one client can’t have more than one request in the queue at a time anyway) and so doesn’t need the message server.

The client machine queues a request (prefixed with its machine ID) by doing a &PUTMSG to the predetermined file server queue number, then idles in a &SERVE() loop polling the result code after each network transaction handled by the client.  When it finds a result, it returns from the GOSUB and continues execution.

The file server idles polling its input queue with a &GETMSG, and, when it finds a request, it parses it, sets up any required parameters that were not supplied, and executes the command on the local file system.

If a data transfer is required, it is &PEEKed and BSAVEd or BLOADed and &POKEd in chunks up to some maximum (like 4KB, to keep network latency reasonable).  When the command is complete, the result code, and any address and EOF information, is &POKEd to the requester, and the server goes on to the next request in its queue.

Performance seems to be quite good, limited primarily by device latency and/or network bandwidth (>10KB/sec).

After I get a little further down the road (and get back from a short trip) I’ll complete testing and do some performance characterization.

When that’s satisfactory, I’ll be writing it up and posting it on my web site for people to play with, or just take a look at.  I think there is some value in publishing code that implements modest network functionality concisely.

 

-michael

NadaNet networking for Apple II computers! Home page:  http://members.aol.com/MJMahon/