Art-Net vs sACN

Once you’ve patched a fixture and know what a universe is, the next question is how that universe actually gets to your lights over a network. Art-Net and sACN (E1.31) are the two protocols that do this, and they don’t work the same way underneath. This page covers what each one is, how it reaches the network, how the two number universes differently, and when to use which — there’s nothing to click in your own project, just a look at where the settings live.

Two protocols, one job: getting DMX onto the network

Art-Net and sACN both carry DMX512 universes over an ordinary Ethernet/IP network instead of a dedicated DMX cable, so one network connection can carry many universes at once. That’s where the similarity ends: they’re separate, independent industry standards, and they reach the network in different ways. A node, console or visualizer might speak one, the other, both, or neither — that’s why Relackout offers both as separate outputs.

Art-Net: broadcast over Ethernet

Art-Net’s classic, simplest mode is broadcast: a packet goes out to every device on the network, and each node decides for itself whether it cares about the universe inside. The protocol itself also allows unicast (straight to one node) and other delivery modes, but Relackout’s Art-Net output only broadcasts — there’s no unicast option. It sends on UDP port 6454 to the network’s broadcast address (something like 192.168.1.255).

sACN (E1.31): multicast with priority

sACN sends each universe to its own multicast group, meant only for the devices that have joined that group — unlike Art-Net’s broadcast, on a network whose switches handle IGMP properly, uninterested devices never see the traffic at all. Relackout sends every active sACN universe under the source name “Relackout”. sACN also carries a priority value with every packet, which Art-Net doesn’t have — more on that below.

Universe numbering: 0-based on the wire, U1 in Relackout

Art-Net numbers universes starting from 0 on the wire. Relackout’s interface, to stay consistent with how you patch fixtures, always shows universes starting from 1 (U1, U2, U3, U4). The Universe base setting bridges the two: set it to 0 (standard, 0-based) and U1 goes out on the wire as universe 0 — the default, and what most nodes and media servers expect; set it to 1 (1-based) and U1 goes out as universe 1 instead, matching the few nodes or viewers that count that way themselves.

sACN doesn’t need an equivalent setting. The E1.31 standard itself treats universe 0 as invalid — valid universe numbers start at 1 — so Relackout’s U1–U4 already line up one-to-one with the universe numbers sACN puts on the wire, with no base to choose.

Priority in sACN

Every sACN source tags its packets with a priority from 0 to 200 (100 by default). If more than one source sends to the same universe — a backup console sitting ready behind your main one, say — the receiving device uses the data from whichever source has the higher priority; what happens between sources at the same priority isn’t set by the standard — many receivers merge them channel by channel, taking the highest value per channel (HTP). Art-Net has no priority field at all — nothing marks one source as the main one and another as the backup; an Art-Net node that gets the same universe from two sources simply merges them (HTP by default). In Relackout, Priority is a single number (0–200, default 100) that applies to every sACN universe this workspace sends.

When to use which

Start from what your node, console or visualizer actually speaks. Art-Net is older and very widely supported — most budget Ethernet-DMX nodes default to it, and it’s simple enough for a small, single-subnet setup like one bar or one stage. Because Relackout’s Art-Net is broadcast-only, though, leaving unused universes switched on wastes bandwidth on busy or wireless networks — see Fixing lag on Wi-Fi for what that costs you. sACN’s multicast delivery avoids that waste on larger, managed networks where the switches handle IGMP properly, and its priority field is the only one of the two that supports a clean backup-source setup; on a small, unmanaged network, that multicast advantage can disappear and packets end up reaching everyone anyway. Relackout doesn’t make you choose: both outputs share the same universe limit from your plan, and you can leave both switched on if your gear is happy with either.

Where you see it in Relackout

1. 1

   Open Settings from the home screen.

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2. 2

   Scroll down to the DMX Outputs heading; see the Art-Net card’s Broadcast universes row (only U1 selected) and the Universe base select below it.

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3. 3

   Scroll further down, past the USB DMX card, to the sACN (E1.31) card: the sACN output switch (off), the Priority field (100) and the Universes buttons (U1–U4 all selected).

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What’s next

Art-Net broadcasts to everyone and numbers universes from 0 on the wire; sACN multicasts only to subscribers, numbers universes from 1, and adds a priority value Art-Net doesn’t have. For the full walkthrough of setting up either output — along with USB DMX — see DMX output: Art-Net, sACN and USB DMX; for the network address settings behind the Art-Net card, see Connection settings; and if Art-Net’s broadcast traffic is causing lag on a Wi-Fi node, see Fixing lag on Wi-Fi.