# 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.)  It is intented to be
used with the Apple II client program `VEDRIVE.SYSTEM` which is included as
part of the [ADTPro](https://github.com/ADTPro/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.

## 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.

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

There are only a few options:

 - `-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. 

## 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.