Last week we discussed RDM, a networking protocol for management and monitoring of different devices connected over a DMX network. This week we’re talking about Art-Net, a competitor to sACN, which both carry DMX data. The biggest advantage to Art-Net over SACN is its capability to carry RDM data. While its theoretically possible to use RDM over sACN E1.31, it is not supported. Art-Net uses many nodes and one server to communicate. Allowing different nodes to subscribe to publisher nodes which send the data.

Art-Net uses two different groups of packets, discovery and streaming. All packets are sent over UDP meaning a faster protocol but less reliability that the packet will get to its source. Discovery consists of two main packet types, ArtPoll and ArtPollReply. ArtPoll broadcasts that a node is interested in finding who else is connected to that network and all devices, including the sender, respond with an ArtPollReply containing info about the device like its IP, manufacturer info, and human readable reports on its status. The main streaming packet is ArtDmx which is sent to a specific port address for nodes to process DMX data. These packets only contain changes in data and are not intended to be sent every frame. While this is true, a node should expect a ‘Keep-Alive’ packet every 4 seconds affirming the current state. In streaming there are also packet types to keep a show synchronous or non-synchronous. There are also packet types to set the real time clocks in devices and to send macro triggers to the network. Along with these there are file transfer packets to update the firmware on lights.

The website art-net.org.uk contains some useful C++ code snippets describing how to program the protocol.

Sources:

https://art-net.org.uk/