Nodes with more than four ports
The Art-Net 4 protocol simplifies the way in which a gateway with more than 4 ports publishes itself to the console. The console sends out ArtPoll packets to request information from the gateway. The gateway then replies with up to 255 ArtPollReply packets. Each ArtPollReply can describe between 1 and 4 DMX ports.
In the ArtPollReply, the BindIp field must be set to a value identical to the source IP. The BindIndex is used to differentiate the different packets. Values 0 and 1 are used interchangeably and mean the root device. Values from 2 – 255 define the bound ports.
Example 1. Consider a node with 12 DMX output ports and an IP address of 2.0.0.100. The following table shows how the 3 ArtPollReplies could be structured:
An Art-Net controller will parse these packets to discover which Port-Addresses are subscribed to this IP address. It will then unicast to those discovered IP addresses.
Example 2. A product may opt to publish less than 4 ports in each ArtPollReply. In fact their is a benefit to publishing only 1 port per ArtPollReply: each port can then be set to take the full 15-bit address. The following table shows how the 12 ArtPollReplies could be structured:
An Art-Net controller will parse these packets to discover which Port-Addresses are subscribed to this IP address. It will then unicast to those discovered IP addresses.
