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What is Art-Net?

Art-Net is a network protocol for transmitting DMX512 lighting control data over Ethernet and Wi-Fi networks. Developed by Artistic Licence, it enables lighting consoles, visualizers, and control software to communicate with lighting fixtures over standard IP networks.

Protocol

UDP-based protocol on port 6454 (default)

Transport

Standard Ethernet/Wi-Fi (IPv4)

Data Rate

Up to 44 Hz typical refresh rate

Capacity

32,768 universes × 512 channels = 16.7M channels

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DMX512 Basics

DMX512 (Digital Multiplex 512) is the foundation protocol that Art-Net encapsulates.

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Universe Structure

A DMX universe contains exactly 512 channels, numbered 1-512 in DMX terminology or 0-511 in zero-indexed programming. 
Universe 0: Channels 0-511   (DMX 1-512)
Universe 1: Channels 512-1023 (DMX 1-512)
Universe 2: Channels 1024-1535 (DMX 1-512)
...

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Channel Values

Each channel is an 8-bit value (0-255):
  • 0: Off / Minimum
  • 128: 50% intensity
  • 255: Full / Maximum
In HNode’s internal representation, channels are zero-indexed and stored in a contiguous List<byte>, making Universe 3, Channel 5 accessible at index (3 × 512) + 5 = 1541.

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Art-Net in HNode

HNode uses the ArtNetReceiver component to listen for Art-Net packets on the network.

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Network Configuration

1

Bind Address

Configure the IP address HNode listens on:
  • 0.0.0.0 (Default): Listen on all network interfaces
  • Specific IP: Listen only on that interface (e.g., 192.168.1.100)
ArtNetReceiver.cs:58-62
public void ChangeIPAddress(IPAddress address)
{
    ArtNetLogger.LogInfo("ArtNetReceiver", 
        $"Changing IP Address from {UdpReceiver.Address} to {address}");
    UdpReceiver.ChangeIPAddress(address);
}
2

Port Configuration

Art-Net uses UDP port 6454 by default, but HNode allows customization:
ArtNetReceiver.cs:48-53
public void ChangePort(int port)
{
    ArtNetLogger.LogInfo("ArtNetReceiver", 
        $"Changing port from {UdpReceiver.Port} to {port}");
    UdpReceiver.ChangePort(port);
}
3

Automatic Discovery

HNode responds to Art-Net Poll packets, allowing lighting consoles to automatically discover it on the network.

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Packet Reception

When an Art-Net packet arrives, HNode processes it through the following flow:
1

UDP Reception

The UdpReceiver receives raw bytes from the network socket.
2

Packet Parsing

The ArtNetPacket.Create() method parses the header and identifies the packet type (DMX, Poll, PollReply).
ArtNetReceiver.cs:74-94
private void OnReceivedPacket(byte[] receiveBuffer, int length, EndPoint remoteEp)
{
    var packet = ArtNetPacket.Create(receiveBuffer);
    if (packet == null) return;
    LastReceivedAt = DateTime.Now;
    
    switch (packet.OpCode)
    {
        case OpCode.Dmx:
            _onReceivedDmxEvent?.Invoke(ReceivedData<DmxPacket>(packet, remoteEp));
            break;
        case OpCode.Poll:
            _onReceivedPollEvent.Invoke(ReceivedData<PollPacket>(packet, remoteEp));
            break;
        // ...
    }
}
3

Universe Storage

The DmxManager stores the 512-byte DMX data in a dictionary keyed by universe number.
DmxManager.cs:64-75
public void ReceivedDmxPacket(ReceivedData<DmxPacket> receivedData)
{
    var packet = receivedData.Packet;
    var universe = packet.Universe;
    if (!DmxDictionary.ContainsKey(universe)) 
        DmxDictionary.Add(universe, packet.Dmx);
    Buffer.BlockCopy(packet.Dmx, 0, DmxDictionary[universe], 0, 512);
}
HNode only stores universes that have been received. Empty universes don’t consume memory until their first packet arrives.

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DMX Universe Management

The DmxManager provides a clean interface for accessing DMX data:

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Accessing Universe Data

// Get all active universes
ushort[] universes = dmxManager.Universes();

// Get DMX values for a specific universe
byte[] dmxValues = dmxManager.DmxValues(universe: 2);
// Returns 512-byte array (returns zeros if universe doesn't exist)

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Universe Merging

During rendering, HNode merges all universes into a single contiguous list:
TextureWriter.cs:80-95
var universeCount = dmxManager.Universes().Max() + 1;
mergedDmxValues.Capacity = universeCount * 512;

for (ushort u = 0; u < universeCount; u++)
{
    byte[] dmxValues = dmxManager.DmxValues(u);
    mergedDmxValues.AddRange(dmxValues);
}
This creates a flat channel array: 
[Universe 0: ch0-511][Universe 1: ch0-511][Universe 2: ch0-511]...

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Channel Addressing

HNode supports multiple channel addressing formats:

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Global Index

A single integer representing the absolute channel position: 
channel: 1541  # Channel 1541 globally

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Universe.Channel Notation

Dotted notation for clarity: 
channel: 3.5  # Universe 3, Channel 5

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Equation Support

Channel values can use mathematical expressions: 
channel: (3 * 2).(5 * 5)  # Universe 6, Channel 25
DMX fixtures use 1-indexed channels (1-512), but HNode internally uses 0-indexed (0-511). When configuring fixtures, subtract 1 from the DMX channel number.

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Art-Net Discovery & Polling

HNode implements the Art-Net discovery protocol, allowing it to be automatically found by lighting consoles.

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Poll Response

When a Poll packet is received, HNode responds with device information:
DmxManager.cs:96-125
var responsePacket = new PollReplyPacket
{
    IpAddress = ipBytes,
    Port = ArtNetReceiver.Port,
    VersionInfo = 0x0000,
    NetSwitch = 0,
    SubSwitch = 0,
    Status1 = status,
    ShortName = "HNode",
    LongName = "HNode by Happyrobot33",
    NodeReport = "All systems functional",
    NumPorts = ushort.MaxValue,
    // ...
};
This allows lighting consoles to:
  • Discover HNode on the network
  • Display it in device lists
  • Show connection status
  • Configure universe routing

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Connection Status

HNode tracks whether Art-Net data is being received:
ArtNetReceiver.cs:37-38
public DateTime LastReceivedAt { get; private set; }
public bool IsConnected => LastReceivedAt.AddSeconds(1) > DateTime.Now;
If IsConnected is false, check:
  1. Art-Net source is sending to the correct IP/port
  2. Firewall isn’t blocking UDP 6454
  3. Network interfaces are configured correctly

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Performance & Throughput

HNode displays real-time performance metrics:
TextureWriter.cs:166-172
frameTime.text = $"Serialization Time: {timer.ElapsedMilliseconds} ms";
frameTime.text += $"\nDMX Channels: {mergedDmxValues.Count}";
var bytesPerSecond = mergedDmxValues.Count / UnityEngine.Time.smoothDeltaTime;
var prettyBytes = ByteSize.FromBytes(bytesPerSecond).ToString("0.##");
frameTime.text += $"\nData Throughput: {prettyBytes}/s";

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Typical Performance

3 Universes

1,536 channels~90 KB/s @ 60 FPS

10 Universes

5,120 channels~300 KB/s @ 60 FPS

32 Universes

16,384 channels~960 KB/s @ 60 FPS

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Multi-Universe Example

Here’s how a typical stage lighting setup maps to universes: 
Universe 0: House lights (128 channels)
Universe 1: Stage wash fixtures (256 channels)
Universe 2: Moving heads (180 channels)
Universe 3: LED strips (512 channels)
Universe 4: Effects projectors (96 channels)
HNode receives all five universes, merges them into a 2,560-channel array, processes through generators, and serializes to video:
1

Art-Net In

5 universes received over network
2

Merge

Flattened to channels 0-2559
3

Process

Generators modify specific channel ranges
4

Serialize

VRSL converts to 1920×1080 texture
5

Output

Spout sends to VRChat/Unity

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Troubleshooting Art-Net

  1. Check HNode is listening on the correct IP (0.0.0.0 for all interfaces)
  2. Verify Art-Net source is sending to the correct port (6454 default)
  3. Disable Windows Firewall or add exception for UDP 6454
  4. Ensure no other application is using port 6454
  5. Try binding to a specific IP instead of 0.0.0.0
  1. Check SerializeUniverseCount is high enough in show config
  2. Verify Art-Net source is sending the correct universe numbers
  3. Use the DmxManagerViewer editor tool to inspect received universes
  4. Ensure universe numbers don’t exceed HNode’s capacity
  1. Reduce SerializeUniverseCount to only needed universes
  2. Lower target framerate to 30 FPS
  3. Use a more efficient serializer (Binary instead of VRSL)
  4. Disable unnecessary generators and exporters
  5. Check network bandwidth if receiving many universes
Art-Net is a registered trademark of Artistic Licence Holdings Ltd. HNode is an independent implementation and is not affiliated with Artistic Licence.

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