What’s Missing?

Prior to Evan and Austin’s breakthroughs, here is all we knew:

By setting up a managed switch to mirror traffic sent directly between CDJs, we have been able to see how the Link Info operation is implemented: The players open a direct TCP connection between each other, and send queries to obtain the metadata about tracks with particular rekordbox ID values.

Using an Ethernet switch with port mirroring was, as we hoped, very helpful. As can be seen in the packet capture, which shows a CDJ with IP address 169.254.192.112 booting, the new CDJ opens two TCP connections to the other CDJ at 169.254.119.181.

The first session (given id 0 by Wireshark), which begins at packet 206, connecting to port 12523, determines the port to use for metadata queries.

The second TCP connection (Wireshark display filter tcp.stream eq 1), beginning at packet 212 and connecting to port 1051, shows the track information used by the Link Info display passing between the CDJs. You can see packets reflecting the initial display of a track that was already loaded, then new information as the linked CDJ loaded three other tracks.

There is another capture, with more Link Info streams to be studied (all of the odd numbered tcp.stream values in Wireshark are the relevant ones).

There are still many values with unknown meanings described above, and undoubtedly menu types that have yet to be explored; I have focused on the ones that will be immediately useful to Beat Link Trigger. Contributions of additional research and insight are eagerly welcomed—I would have not gotten nearly this far without help!

In order to offer metadata, timecode, waveforms, and so on, when there are four actual CDJs on the network, it is necessary get the data using a different mechanism. See the Crate Digger project for the solution we have found.

Before we discovered how to ask players for metadata about particular tracks, we did some research into the underlying rexordbox database. The database format is called DeviceSQL and there used to be a free quick start suite at http://java.sys-con.com/node/328557 for working with it, but that site no longer exists because the original (California) company Encirq was acquired by the Japanese Ubiquitous Corporation in 2008. It seems to still be available, but I’d be surprised if they wanted to help out an open source effort like this one.

Performing a packet capture while rekordbox is running reveals that the CDJs send unicast packets to the rekordbox address on port 50000, in addition to the packets they normally broadcast on that port. Figuring out how to pose as rekordbox might be useful in order to see what additional data these can offer, although that may be much more work than posing as a CDJ.

If you have access to Pioneer equipment and are willing to help us validate this analysis, and perhaps even figure out more details, you can find the tool that is being used to perform this research at: https://github.com/deep-symmetry/dysentery