Use Serial / UDP commands
BrightSign players support sending and receiving unlimited Serial and UDP commands. To set up the player to receive these commands, you must define the serial/UDP strings in BrightAuthor Classic. The strings can be used to switch from one file to another, pause, resume, change volume, send output, etc.
BrightSign players also support HTTP communication over TCP through custom scripts.
UDP (Ethernet/Wireless) Commands
Control options for BrightAuthor Classic are described in this video.
The UDP and UDP Input pages contain related info and this page describes how to import multiple commands and filenames as a CSV.
Serial Commands
BrightSign players with a serial port support the sending and receiving of bytes as well as strings (see the this FAQ for more info). When sending or receiving bytes, you must use decimal values. Many websites have tools for converting between decimal, hex, and ASCII values (see here or here). You can also use a standard Windows calculator (select Programmer mode in View) to convert between hex and decimal.
This tutorial video describes how to send serial commands to put a monitor into a power-save mode at specified times using BrightAuthor (our legacy software).
Scripts
You can also control a player through a script. The sample control script below defines a fixed set of playback commands (Play, Stop, Search, Loop, Pause, Resume, etc), and a Readme. Just copy the autorun.brs script and your content to a microSD card, and you're ready to send/receive commands. The script also provides feedback when a command is received, when a file is found, when a file loops, etc.
BrightAuthor Classic assumes the incoming string on serial commands is terminated with a carriage return. This can be changed under File > Presentation Properties.