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Local Doors — 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.

No emulator on the server? See Native v86 Emulation — ENiGMA½ includes a built-in x86 emulator. Raw FreeDOS .img images are compatible between QEMU and v86, so you can set up your image with QEMU and run it with v86 in production.

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.

Multiple concurrent sessions of the same QEMU image are not safe. Each node needs its own image copy, or use Native v86 Emulation which isolates each session automatically.

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.