Why Protocols Decide What You Can Control
AV control protocols are the languages a control system uses to talk to devices. A control system can only operate a device if it speaks that device's protocol — so the breadth of protocol support directly determines how many brands and device types you can drive from one interface.
This is why protocol coverage is the single most practical thing to check when choosing AV control software. A platform that covers the seven protocols below can control almost anything in an exhibition hall, meeting room, or factory floor. This guide explains each one in plain language and shows which devices use it.
The Core Control Protocols
| Protocol | Transport | Typical devices | Direction |
|---|---|---|---|
| TCP | Network (IP) | Displays, matrices, processors | Two-way |
| UDP | Network (IP) | Media players, light controllers | One-way (fast) |
| HTTP (GET/POST) | Network (IP) | Web-API devices, modern AV | Two-way |
| PJLink | Network (IP) | Projectors | Two-way |
| Wake-on-LAN | Network (IP) | PCs, players | One-way (power on) |
| Serial RS-232/485 | Cable | Projectors, screens, legacy AV | Two-way |
| Modbus TCP/RTU | Network / serial | Industrial & building devices | Two-way |
TCP — reliable two-way network control
TCP opens a connection, sends a command, and can read a response. Use it when you need confirmation that a command landed — switching a video matrix input, querying a display's power state. It is the workhorse for modern networked AV.
UDP — fast, fire-and-forget
UDP sends a packet without waiting for acknowledgement. It is ideal for simple, frequent commands where speed matters more than confirmation — triggering a media player, sending a scene cue. Lower overhead, no connection to maintain.
HTTP GET / POST — for web-API devices
Many modern devices expose a REST-style web API. An HTTP GET hits a URL (often with a query string); a POST sends a request body. Use this for gear controlled through a web endpoint, or for integrating with other software systems.
PJLink — the projector standard
PJLink is a manufacturer-independent standard for projectors. One protocol powers projectors on/off, switches inputs, and reads lamp/error status across brands — no per-brand command tables. If you control projectors, PJLink is the cleanest path. (See the projector control guide.)
Wake-on-LAN — remote power-on for PCs
Wake-on-LAN sends a "magic packet" to power on a networked PC or media player from standby — essential for unattended morning startup in galleries and showrooms.
Serial RS-232 / RS-485 — the AV backbone
Serial remains the most universal AV device control. RS-232 is point-to-point; RS-485 supports multi-drop over longer distances. Most projectors, screens, switchers, and legacy AV gear accept serial command strings. Serial can run directly from a COM port or be tunneled over the network (serial-over-TCP). (See serial communication guide.)
Modbus TCP / RTU — bringing industrial gear in
Modbus is the standard for industrial and building automation devices — PLCs, energy meters, HVAC, sensors. Modbus TCP runs over the network; Modbus RTU over serial. Supporting Modbus lets one control system span AV and industrial monitoring. (See industrial Modbus dashboard.)
Two-Way Control: Reading Status, Not Just Sending
Sending a command is only half the job. Protocols that read responses (TCP, HTTP, PJLink, Modbus) let the control system show device status — is the projector actually on, what input is live, what is the temperature reading. This feedback turns a blind remote into a real dashboard and is what separates a basic controller from a reliable one.
How SoftControl Uses These
SoftControl is software-based AV control that speaks all of the above: udp, tcp, http_get, http_post, pjlink, wol, serial, serial-over-TCP, modbus_tcp, and modbus_rtu. You configure a command's protocol, target, and payload in the visual editor — no programming — and the same interface can drive a projector over PJLink, a screen over RS-232, and a factory line over Modbus, all at once.
FAQ
What protocol do projectors use?
Most projectors support both serial RS-232 and the network standard PJLink. PJLink is usually simpler because it is brand-independent for power, input, and status.
What is the difference between TCP and UDP for AV control?
TCP is connection-based and confirms delivery (good for status queries and matrix switching). UDP is connectionless and fast (good for simple, frequent triggers). Many systems use both depending on the device.
Can one control system use multiple protocols at once?
Yes. A capable system like SoftControl assigns a protocol per command, so a single interface can mix PJLink, RS-232, TCP, and Modbus across different devices simultaneously.
Control Any Protocol from One Interface
SoftControl speaks TCP, UDP, HTTP, PJLink, Wake-on-LAN, serial, and Modbus — configured visually, no programming. Download and trial free, no registration.
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