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OpenProLink

Open-source Pioneer DJ / AlphaTheta Pro DJ Link hardware simulator (CDJ-3000 / XDJ) and full-protocol capture suite (CDJ / XDJ / DJM mixers).

OpenProLink has two tools:

• prolink-probe records what real Pioneer players and mixers send: every packet kind with its send rate, raw hex samples, a decoded view and a map of the bytes that changed while you worked the controls. One run on your gear gives developers what they otherwise need the hardware on their desk for.
• cdj3000-sim is a software player for Pro DJ Link test benches. It joins the link as a virtual CDJ-3000 and serves a rekordbox USB stick to the device under test. You watch and control it from a web page: what the deck sends, what the other side understands, and every packet in between.

It was built for EngineX OS, the custom system for Denon DJ / Numark / Rane standalone units, which talks Pro DJ Link to Pioneer players.

Status: early. The simulator's packet layouts follow Deep Symmetry's protocol analysis (dysentery, beat-link, crate-digger). A passing run proves that the device under test and this simulator agree; only real hardware proves compatibility. That is why captures from real players and mixers matter: please send one.

Capture your hardware with prolink-probe

Wanted: CDJ-3000, CDJ-2000NXS2, XDJ-AZ, XDJ-XZ, DJM-A9, DJM-V10, DJM-900NXS2, and any other Pro DJ Link player or mixer.

Method 1: Download a prebuilt package

No Go installation is needed. Download Windows 64-bit, macOS Apple Silicon, macOS Intel, Linux x86-64, or Linux ARM64.

1. Connect the computer and CDJ / XDJ / DJM devices by Ethernet, or to the same switch or router. Quit other Pro DJ Link software.
2. Extract the archive. On Windows, double-click run-capture.bat; on macOS, double-click run-capture.command. On macOS or Linux you can also run ./prolink-probe -duration 45s -out prolink-report.md -json prolink-samples.json in a terminal.
3. During the 45 seconds, load a USB track and use PLAY, CUE, MASTER, BEAT SYNC and the pitch fader. On a DJM, move each channel fader and the crossfader, change Beat FX, adjust FX Time and Level, and toggle ON/OFF. Perform actions one at a time and note their approximate times.
4. Review prolink-report.md and prolink-samples.json in the extracted folder, then attach both to a Hardware Capture Issue with your models, firmware and action times. Known IP and MAC fields are replaced, but other private data can remain; see Privacy below.

Method 2: Run from source

1. Connect your computer to the same switch or router as the devices (or to the LAN port of an XDJ-XZ / XDJ-AZ). Quit rekordbox and any other Pro DJ Link software, which hold the same ports.

2. Install Go 1.26 or newer, then run from a checkout of this repository:

   go run ./cmd/prolink-probe -duration 60s -out capture.json

   Allow incoming connections if macOS or Windows asks. Ctrl-C ends the capture early and still writes the report.

3. During the 60 seconds, do one action at a time, about 3 seconds apart, and write down roughly when you did each one (see the table below).

4. Review capture.json, then attach it to a hardware capture issue with your models, firmware versions, how they are connected and your list of actions.

Device	Actions that reveal the most
CDJ-3000 / CDJ-2000NXS2	Load a track from USB, Play / Pause, move the tempo fader, change the tempo range, Master Tempo on/off, Quantize on/off, MASTER on this deck then on another, SYNC on/off, a loop, a hot cue, eject
XDJ-AZ / XDJ-XZ	The player actions above on each deck, plus the mixer section: each channel fader up and down, crossfader, Beat FX on/off, change the effect, turn the beat / TIME knob and the level/depth knob, Quantize
DJM-A9 / DJM-V10 / DJM-900NXS2	Each channel fader up and down one at a time (the players' on-air ring follows), crossfader, Beat FX on/off, change the effect and its channel, beat buttons (1/2, 1, 2 …), TIME knob, level/depth, the mixer's Quantize, tap or auto BPM

What the probe does

By default it listens for 1.5 s, then joins the link as a virtual player on the first free number from 7 to 15 (players use 1–6, rekordbox 0x11 and up, mixers 0x21 and up) and announces itself every second. Players and mixers unicast most of their traffic only to devices they have seen announce, so without this step a computer hears little more than keepalives and beats. It then:

• sends each player a media query (0x05) for USB and SD and records the media response (0x06);
• opens each player's dbserver (TCP 12523 port query, greeting, setup, root menu and render) and keeps every message as raw hex plus decoded arguments. Players refuse dbserver clients numbered above 4, so it asks as the target player's own number, as beat-link does;
• records everything received on UDP 50000, 50001 and 50002: keepalives, CDJ status 0x0a, mixer status 0x29, beats 0x28, the CDJ-3000's 30 ms precise position 0x0b, channels on air 0x03, master handoff 0x26/0x27, sync control 0x2a, and any kind nobody has documented yet.

It never sends status, beat, master, sync, fader or load commands. If a device takes its number it moves to another one. -passive only listens and sends nothing.

Flag	Default	Meaning
-duration	15s	How long to capture; use 60 s or more while you work the controls
-out	capture.json	Report file
-passive	off	Listen only: no announcement, no queries (players then send far less)
-number	first free 7–15	Virtual player number to announce
-iface	the one on the devices' subnet	Network interface to announce on
-samples	16	Raw hex samples kept per packet kind, at most one per second

What is in the report

Key	Contents
devices	Every device heard: name, player number, device class, firmware (from its status), when it was first seen
streams	One entry per (device, port, type, subtype, length): packet count, interval in ms (avg/min/max), the last packet decoded, raw hex samples
streams[].changed_bytes	Every offset that changed during the capture, with its known meaning or none (an undocumented field), first/last/min/max value, number of changes, distinct values, and the times of the first and last change. Match those times to your list of actions to find the byte behind a knob
media_queries	Each 0x05 sent and whether the player answered
dbserver	Per player and slot: dbserver port, root menu items and the full message transcript
notes	The player number used, number changes, problems such as no traffic heard

Privacy. IP and MAC addresses inside packets are replaced with stand-ins (10.0.0.x, 02:00:00:00:00:xx). Every other byte is kept exactly as received, including the USB stick's name and the track IDs. A four-byte value that matches a real IP address outside the places the protocol keeps addresses is listed under unredacted_ip_like and left untouched; check those before posting.

Simulator

Panel	What you get
Virtual CDJ-3000	Player number 1–4, Play / Pause / Cue, tempo ±6 / ±10 / ±16 % / WIDE, beat counter, scrolling 3-band waveform and overview, USB track list, audio in the browser
Device under test	The EngineX OS Pro DJ Link receiver running in-process: the players, BPM, pitch, beat and play state it decodes, and the waveform it fetched over NFS
CDJ → Denon import	Copies the virtual USB over NFSv2 and runs EngineX's rb-bridge, then lists the Engine playlists it built
[LINK] Denon → CDJ	Browses the EngineX export with a dbserver client (TCP 12523), loads a track over NFSv2, shows its waveform and plays it; shows the export yielding its player number on a collision
Wire inspector	UDP 50000 keepalive, 50001 beat + 30 ms 0x0b playhead, 50002 status + 0x05/0x06 media query, dbserver requests and NFS reads, with the first bytes of each in hex

The default USB stick is generated: 32 bars of 120 BPM drums with a matching beatgrid, PWV5 colour and PWV7 3-band waveforms. Pass -usb to use a real rekordbox export.

Quick start

Build and run on a Linux host (it uses the loopback addresses 127.0.0.1 and 127.0.0.2, and UDP ports 50000–50002):

go build -trimpath -o bin/cdj3000-sim ./cmd/cdj3000-sim
./bin/cdj3000-sim -http 127.0.0.1:18300                # generated USB stick
./bin/cdj3000-sim -usb /path/to/USB -http 127.0.0.1:18300

The web page listens on loopback only. From your laptop:

ssh -L 18300:127.0.0.1:18300 <build host>
open http://127.0.0.1:18300

Flag	Default	Meaning
-http	127.0.0.1:18300	Web UI address. Keep it on loopback
-usb	generated	rekordbox USB root with PIONEER/rekordbox/export.pdb
-sim-ip	127.0.0.2	Address the virtual CDJ sends from and serves NFS on
-denon-ip	127.0.0.1	Address the device-under-test receiver listens on
-denon-empty	off	The Denon drive holds no rekordbox export of its own
-deck	none	IPv4 of real EngineX decks on the LAN to play to, separated by commas (set -sim-ip to this host's LAN address)
-ableton-link	off	Publish tempo and bar phase as an Ableton Link session

Repository layout

Path	Contents
cmd/prolink-probe/	The capture tool and its tests against simulated CDJ-3000 and DJM-V10 hardware
cmd/cdj3000-sim/	The simulator: playhead clock, generated USB stick, reverse link and web UI
pkg/cdj/	Independent CDJ-side packet builders/parsers (0x06, 0x0a, 0x28, 0x0b, 0x05/0x06), dbserver client, ANLZ parser and captured-wire tests
third_party/enginex/	Read-only copy of the EngineX OS packages under test. Refresh with scripts/sync-enginex.sh, never edit
docs/ARCHITECTURE.md	Components, data flow, test strategy and roadmap
docs/PROLINK-WIRE-SPEC.md	Every packet the simulator sends or parses, byte by byte

Trademarks

Pioneer DJ, CDJ, XDJ, DJM, rekordbox and Pro DJ Link are trademarks of AlphaTheta Corporation. Denon DJ and Engine DJ are trademarks of inMusic Brands. This project is not affiliated with or endorsed by either company. Model names describe the hardware it emulates or records.

License

MIT. third_party/enginex is EngineX OS code under its own MIT license.