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ProDOS-Utils/README-veserver.md

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VEServer - Virtual Ethernet Drive Server for Apple II

Purpose

VEServer is a very simple virtual disk server for an Apple II equipped with a compatible ethernet card (such as the Uthernet II.) VEServer can run on Linux, Mac or Windows, provided Python v3 is installed. It is intended to be used with the Apple II client program VEDRIVE.SYSTEM which is included as part of the ADTPro disk imaging program.

ADTPro's VEDRIVE.SYSTEM program is designed to communicate with the ADTPro server, which is a multi-platform Java program. VEServer can be used in place of the ADTPro server for this purpose. VEServer is a much smaller and simpler program, so it is easier to modify and better suited to being run as a system service.

VEServer can also support RS232 serial connections, in which case ADTPro's VSDRIVE.SYSTEM should be used on the Apple II rather than VEDRIVE.SYSTEM. The default mode of operation is to use ethernet. See the Command Line Options section below for information on how to switch to serial mode.

Principle of Operation

VEServer uses IPv6 and listens on UDP port 6502 for incoming datagrams from VEDRIVE.SYSTEM. There are two types of supported request:

  • Read disk block and obtain updated system date and time
  • Write disk block

Two simulated drives are supported, backed up by disk files in .po "ProDOS Order". These may be 143K or 800K floppy disk images or any volume up to the ProDOS limit of 32MB. .2mg container files are also supported, provided the volume within the .2mg file is in ProDOS order.

VEServer can provide system date and time in a similar manner to an Apple II clock such as Thunderclock or No Slot Clock. Because the legacy ProDOS date and time format will run out in a few years time, ProDOS 2.5 introduces a new date and time format. VEServer uses the legacy format by default. If using ProDOS 2.5 please specify the --prodos25 flag to use the new format.

Command Line Options

VEServer accepts the following command line options; each option has a short form and a verbose form:

  • -h, --help - Display brief usage information.
  • -p, --prodos25 - Use new ProDOS 2.5 date/time format (see above.)
  • -1 FNAME, --disk1=FNAME - Specify filename for disk 1 image.
  • -2 FNAME, --disk2=FNAME - Specify filename for disk 1 image.
  • -s, --serial - Use RS232 serial rather than Ethernet.
  • -b nnnnn, --baud=nnnnn - Specify baud rate when using serial connection.

If the --disk1=FNAME or --disk2=FNAME options are not specified, VEServer will fall back to using the default values hard coded at the top of the Python script.

Running in a Shell

You can just run veserver.py directly, for example ./veserver.py --prodos25 -1 /home/woz/hd32_1.po -2 /home/woz/hd32_2.po.

When run in a shell, each block number read or written is logged, and vt100 escape codes are used to colourize the output. Reads are shown in green and writes in red. If a block number is prefixed by a + symbol this indicates that VEServer believes this is a duplicate request, which is usually caused by UDP packet loss. If a block number is shown prefixed by X, this indicates a checksum failure (not seen in normal operation.)

Running as a System Service using Systemd

A sample Systemd unit file veserver.service is provided. This has been tested on Raspbian (Raspberry Pi) but may need modifications for other distributions of Linux. On most systems you just need to edit the veserver.service file to reflect the path where veserver.py is installed and copy it to /lib/systemd/system.

Once the service file has been installed, you can control the veserver service as follows:

  • systemctl start veserver
  • systemctl status veserver

The reads and writes are logged to the system log and may be seen using the following command:

  • systemctl stop veserver

Rather than using colour to indicate reads and writes the letter 'R' or 'W' is shown before the block number in the log.

Working with Multiple Apple II Clients (Advanced)

If you use VEDRIVE.SYSTEM on more than one Apple II machine, it is sometimes convenient to be able to use different disk images on each machine. VEServer offers a way to do this.

Suppose the disk1 filename is set to virtual-1.po and the disk2 filename is set to virtual-2.po (either using the --disk1=FNAME / --disk2=FNAME command line parameters, or using the hard-coded default.) Further, suppose the IP address of the Apple II client is 192.168.0.100. In this case, when accessing drive 1, VEServer will first look for the file:

  • virtual-1-192.168.0.100.po

If this is found that file will be served. If not found, VEServer will fall back to:

  • virtual-1.po

Similarly for drive 2, virtual-2-192.168.0.100.po will be used if it exists, or virtual-2.po otherwise.

This mechanism allows you to serve different disk images for each client, allowing read/write access with no risk of data corruption due to simultaneous access.