116 lines
4.9 KiB
Markdown
116 lines
4.9 KiB
Markdown
# VEServer - Virtual Ethernet Drive Server for Apple II
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## Purpose
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VEServer is a very simple virtual disk server for an Apple II equipped with
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a compatible ethernet card (such as the Uthernet II.) VEServer can run on
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Linux, Mac or Windows, provided Python v3 is installed. It is intended to be
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used with the Apple II client program `VEDRIVE.SYSTEM` which is included as
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part of the [ADTPro](https://github.com/ADTPro/adtpro) disk imaging program.
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ADTPro's `VEDRIVE.SYSTEM` program is designed to communicate with the ADTPro
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server, which is a multi-platform Java program. VEServer can be used in
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place of the ADTPro server for this purpose. VEServer is a much smaller and
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simpler program, so it is easier to modify and better suited to being run as
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a system service.
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VEServer can also support RS232 serial connections, in which case ADTPro's
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`VSDRIVE.SYSTEM` should be used on the Apple II rather than `VEDRIVE.SYSTEM`.
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The default mode of operation is to use ethernet. See the Command Line
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Options section below for information on how to switch to serial mode.
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## Principle of Operation
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VEServer uses IPv6 and listens on UDP port 6502 for incoming datagrams from
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`VEDRIVE.SYSTEM`. There are two types of supported request:
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- Read disk block and obtain updated system date and time
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- Write disk block
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Two simulated drives are supported, backed up by disk files in `.po` "ProDOS
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Order". These may be 143K or 800K floppy disk images or any volume up to the
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ProDOS limit of 32MB. `.2mg` container files are also supported, provided
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the volume within the `.2mg` file is in ProDOS order.
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VEServer can provide system date and time in a similar manner to an Apple II
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clock such as Thunderclock or No Slot Clock. Because the legacy ProDOS date
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and time format will run out in a few years time, ProDOS 2.5 introduces a new
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date and time format. VEServer uses the legacy format by default. If using
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ProDOS 2.5 please specify the `--prodos25` flag to use the new format.
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## Command Line Options
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VEServer accepts the following command line options; each option has a short
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form and a verbose form:
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- `-h`, `--help` - Display brief usage information.
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- `-p`, `--prodos25` - Use new ProDOS 2.5 date/time format (see above.)
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- `-1 FNAME`, `--disk1=FNAME` - Specify filename for disk 1 image.
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- `-2 FNAME`, `--disk2=FNAME` - Specify filename for disk 1 image.
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- `-s`, `--serial` - Use RS232 serial rather than Ethernet.
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- `-b nnnnn`, `--baud=nnnnn` - Specify baud rate when using serial connection.
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If the `--disk1=FNAME` or `--disk2=FNAME` options are not specified, VEServer
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will fall back to using the default values hard coded at the top of the
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Python script.
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## Running in a Shell
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You can just run `veserver.py` directly, for example
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`./veserver.py --prodos25 -1 /home/woz/hd32_1.po -2 /home/woz/hd32_2.po`.
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When run in a shell, each block number read or written is logged, and vt100
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escape codes are used to colourize the output. Reads are shown in green and
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writes in red. If a block number is prefixed by a `+` symbol this indicates
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that VEServer believes this is a duplicate request, which is usually caused by
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UDP packet loss. If a block number is shown prefixed by `X`, this indicates
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a checksum failure (not seen in normal operation.)
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## Running as a System Service using Systemd
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A sample Systemd unit file `veserver.service` is provided. This has been
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tested on Raspbian (Raspberry Pi) but may need modifications for other
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distributions of Linux. On most systems you just need to edit the
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`veserver.service` file to reflect the path where `veserver.py` is installed
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and copy it to `/lib/systemd/system`.
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Once the service file has been installed, you can control the `veserver`
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service as follows:
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- `systemctl start veserver`
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- `systemctl status veserver`
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The reads and writes are logged to the system log and may be seen using the
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following command:
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- `systemctl stop veserver`
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Rather than using colour to indicate reads and writes the letter 'R' or 'W' is
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shown before the block number in the log.
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## Working with Multiple Apple II Clients (Advanced)
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If you use `VEDRIVE.SYSTEM` on more than one Apple II machine, it is sometimes
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convenient to be able to use different disk images on each machine. VEServer
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offers a way to do this.
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Suppose the disk1 filename is set to `virtual-1.po` and the disk2 filename is
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set to `virtual-2.po` (either using the `--disk1=FNAME` / `--disk2=FNAME`
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command line parameters, or using the hard-coded default.) Further, suppose
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the IP address of the Apple II client is 192.168.0.100. In this case, when
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accessing drive 1, VEServer will first look for the file:
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- `virtual-1-192.168.0.100.po`
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If this is found that file will be served. If not found, VEServer will fall
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back to:
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- `virtual-1.po`
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Similarly for drive 2, `virtual-2-192.168.0.100.po` will be used if it exists,
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or `virtual-2.po` otherwise.
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This mechanism allows you to serve different disk images for each client,
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allowing read/write access with no risk of data corruption due to simultaneous
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access.
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