External DOS Emulators

DOS Doors via External Emulators

This page covers running classic DOS door games using external emulators — DOSEMU and QEMU — via the abracadabra module. ENiGMA½ launches the emulator as a child process and bridges I/O over stdio or a socket.

DOSEMU

DOSEMU provides a DOS environment on Linux via stdio. Configure COM1 as a virtual serial port to connect it to ENiGMA½’s stdio bridge.

Step 1: Create dosemu.conf

$_cpu = "80486"
$_cpu_emu = "vm86"
$_external_char_set = "utf8"
$_internal_char_set = "cp437"
$_term_updfreq = (8)
$_layout = "us"
$_rawkeyboard = (0)
$_com1 = "virtual"

$_com1 = "virtual" maps COM1 to stdio — ENiGMA½ speaks directly to the door over stdin/stdout.

Step 2: Create the Door Drive

Create a virtual drive for your door, e.g. /home/enigma/DOS/X/PW, and map it in your DOSEMU AUTOEXEC.BAT:

@echo off
path d:\bin;d:\gnu;d:\dosemu
set TEMP=c:\tmp
prompt $P$G
C:\BNU\BNU.COM /L0:57600,8N1 /F
lredir.com x: linux\fs\home\enigma\DOS\X
unix -e

BNU is a FOSSIL driver installed here at C:\BNU\. A FOSSIL driver is required by most classic DOS doors.

doorPimpWars: {
    desc: Playing PimpWars
    module: abracadabra
    config: {
        name: PimpWars
        dropFileType: DORINFO
        cmd: /usr/bin/dosemu
        args: [
            "-quiet",
            "-f",
            "/path/to/dosemu.conf",
            "X:\\PW\\START.BAT {dropFile} {node}"
        ]
        nodeMax: 1
        tooManyArt: DOORMANY
        io: stdio
    }
}

QEMU

QEMU provides a robust, cross-platform solution for DOS doors. The general approach is a bootstrap shell script that prepares a node-specific GO.BAT, then launches QEMU with the FreeDOS image.

Step 1: Create a FreeDOS Image

Follow the QEMU/FreeDOS guide to create a freedos_c.img. Install FreeDOS, then install your door game at C:\DOORS\LORD\ (or similar).

Transfer files from host to the image using QEMU’s vfat drive:

qemu-system-i386 -localtime /home/enigma/dos/images/freedos_c.img \
    -hdb fat:/path/to/files/to/copy

Files appear on D: inside FreeDOS. Add to the image’s AUTOEXEC.BAT:

CALL E:\GO.BAT

Step 2: Create a Bootstrap Script

This script writes a per-node GO.BAT before launching QEMU:

#!/bin/bash
NODE=$1
DROPFILE=D:\\$2
SRVPORT=$3

mkdir -p /home/enigma/dos/go/node$NODE

cat > /home/enigma/dos/go/node$NODE/GO.BAT <<EOF
C:
CD \FOSSIL\BNU
BNU.COM
CD \DOORS\LORD
COPY /Y $DROPFILE
CALL START.BAT $NODE
FDAPM POWEROFF
EOF

unix2dos /home/enigma/dos/go/node$NODE/GO.BAT

qemu-system-i386 -localtime /home/enigma/dos/images/freedos_c.img \
    -chardev socket,port=$SRVPORT,nowait,host=localhost,id=s0 \
    -device isa-serial,chardev=s0 \
    -hdb fat:/home/enigma/drop/node$NODE \
    -hdc fat:/home/enigma/dos/go/node$NODE \
    -nographic

-chardev socket,... connects COM1 to ENiGMA½’s socket server on $SRVPORT
-hdb fat:... exposes the drop file directory as D:
-hdc fat:... exposes the GO.BAT directory as E:
-nographic runs headless

doorLORD: {
    desc: Playing L.O.R.D.
    module: abracadabra
    config: {
        name: LORD
        dropFileType: DOOR
        cmd: /home/enigma/dos/scripts/lord.sh
        args: [
            "{node}",
            "{dropFile}",
            "{srvPort}",
        ]
        nodeMax: 1
        tooManyArt: DOORMANY
        io: socket
    }
}

DOSBox-X

DOSBox-X is a graphical DOS environment available on Windows, macOS, and Linux. It is primarily useful for preparing disk images — raw .img images created in DOSBox-X are compatible with QEMU and with ENiGMA½’s built-in v86_door.

Using DOSBox-X as a production door server (launching it per user session) is possible but uncommon. The imgmount command can mount raw disk images inside DOSBox-X. See the DOSBox-X documentation for details.