Network terminology
It can pay off to know a bit about networking in general, when working with Art-Net, which relies on ethernet, or when running a show on networked computers. Here we will explain the most commonly used terms and concepts.
Fundamentals
Devices on a network can send information to each other. There are 3 variables that determine if a device will receive the intended network packets.
IP address
Four numbers between 0 and 255, usually separated by dots: 123.123.123.123. Every device on a network needs to have a unique IP address. This address can be set manually or automatically, using DHCP. When working on a show, you usually want to know exactly which device has which IP address and you don't want IP addresses to change automatically, so you need to set the address manually for each device.
Usually, devices using Art-Net are limited to the IP ranges 2.x.x.x or 10.x.x.x. This is not always necessary. For example when using Beam, which only uses Art-Net part A packets, this is not required. For more info, see Art-Net in-depth.
Port
A number between 1024 and 65536. The receiving device needs to be listening on the same port number that the sending device is set to send on. When dealing with Art-Net this variable is never a concern since the only port ever used by Art-Net is number 6454.
Subnet mask
Four numbers, mostly only 0 or 255, usually separated by dots: 255.0.0.0. This is the lesser-known variable. The subnet mask limits which devices on the network can communicate to the device that has the subnet set. Only devices with an IP address with matching fields for where the subnet mask has 255 will be received. For example, with a subnet mask of 255.255.255.0 and an IP address of 10.123.1.40, this device will receive packets from a device with IP address 10.123.1.60, but not from 10.123.2.40 (note the 2).
For the purpose of using Art-Net it is sufficient to know that you always need a subnet mask of 255.0.0.0.
Distribution modes
Unicast versus broadcast
The most common mode for one device to send information to another is to address it directly with its unique IP address. This is called unicast sending.
However, by using 255 in the IP address fields, it is possible to address multiple devices at once. Using 123.123.255.255 as the IP addess to send to will deliver the packages at any device who's address starts with 123.123. Sending to 255.255.255.255 means sending to every device on the network.
Art-Net support in Beam is still relatively simple, meaning the only way to send to more than one Art-Net device is to enter a broadcast IP address in the output settings. When a controller supports Art-Net discovery (the part B protocol), the network is scanned for Art-Net enabled devices.
Pinging a device
Elementary to working with networking from a PC is the ping command. It is used to determine if another device on the network can be found and can receive data from your computer. In short, ping is a command you type in your command line that sends out a few bytes to one or more receivers. Every receiver returns those bytes to the sender. Returned bytes indicate that a receiver is reachable on the network.
Guides to using ping can be found on the internet.
When data from a PC is not received on another PC or on a DMX node, you use ping on the sender to find out if the receiver can be reached via the network at all. If not, the IP address may be incorrectly specified, its subnet mask may prevent connection, or it may simply not be physically connected, indicating perhaps a broken ethernet cable.
Broadcast works with ping just like specifying a unique IP address does. So sending a ping to 255.255.255.255 gives you replies from all devices on your network. This can be useful if you suspect that the unique IP address you use to address a PC or DMX node is incorrect and you want to a quick way to assess what IP addresses do exist on the network.
Hardware
Network connection boxes
There are several types of boxes that multiple devices can plug into so information can be sent from every to every connected device. These different devices are called routers or switches. A router is usually more advanced than a switch, allowing more configuration options and supporting differently labelled ports. Routers can be slower than switches.
When working with Art-Net or networked video playback, you usually simply want to mirror all signals to all connected devices. So we recommend using a simple (unmanaged) switch rather than a router.
Modems are another type of network device that is often encountered, these are used exclusively to connect a network to the internet. This is functionality that you will not need when working with Art-Net or a networked show. Some modems have built-in switch or routing functionality though, in that case they can be used as such.
Cables
The physical cables used to connect devices via ethernet are CAT cables. The CAT standard has several levels of quality, which mostly regards the level of shielding that enables higher data rates. Although Art-Net or Videosync's network connection don't require a high bandwidth at all, it is still advisable to use at least CAT 5 cables, but ideally CAT 5e or higher, to prevent dropped packets.
Wired versus wireless
The terms wireless and wired don't need explanation. But it may be good to mention that although Art-Net and networked video work over a wireless network just as they do over a wired network, the biggest problem with wireless networks is that venues usually have a lot of electromagnetic interference due to the wide variety of electronic devices in use. This can prevent a wireless network from functioning properly. Even if wireless works well when testing in the studio, it can fail when on stage.