MultiDisplayVCP Server v2.0

A high-performance, cross-platform DDC/CI hardware display control daemon. Enables remote control of monitor hardware settings (Brightness, Contrast, Input Source, Audio Volume, Power Mode, and custom VCP codes) across your local network.

Note

Prerequisite: Your physical displays must support DDC/CI and have it enabled in their On-Screen Display (OSD) menu settings.

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🌟 Key Features

• Cross-Platform: Native support for Windows (WinForms GUI / System Tray), Linux (headless daemon / systemd service), and macOS (headless daemon / launchd service).
• Dual-Mode Networking:
  • MagicOnion gRPC / HTTP/2 (Primary): High-throughput, zero-allocation protocol paired with Macro Deck 3 clients.
  • Raw TCP Socket Listener (Legacy / Universal): Fast, text pipe-delimited protocol ensuring backward compatibility with Macro Deck 2 and open integrations (Bitfocus Companion, Stream Deck, Home Assistant, custom scripts).
• Security: HMAC-SHA256 challenge authentication with a sliding timestamp window to prevent replay attacks.
• Hardware Integration:
  • Windows: Windows Monitor Configuration API (dxva2.dll / Physical Monitors).
  • Linux: Kernel I2C interface (ddcutil / /dev/i2c).
  • macOS: I/O Kit Display Services (ddcctl).

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🖥️ Client Compatibility

Client	Protocol	Supported Server Versions
Macro Deck 3 Client (v3.0.0+)	MagicOnion gRPC (HTTP/2) + TCP fallback	Server v2.0+
Macro Deck 2 Client (v2.0.0)	Raw TCP socket	Server v1.x and v2.0+
Bitfocus Companion / Stream Deck / Custom	Raw TCP socket or gRPC	Server v2.0+

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📦 Downloads & Installation

Pre-built packages and installers are available in the Releases section:

Windows

• Recommended Setup Installer: Download and run MultiDisplayVCPServer_Windows_v2.0.0_Setup.exe.
  (Sets up Start Menu & Desktop shortcuts, optional system startup run entry, and registers an uninstaller).
• Portable Archive: Download and extract MultiDisplayVCPServer_Windows_v2.0.0.zip, then launch MultiDisplayVCPServer.exe.

Linux (x64)

1. Install prerequisites:

   sudo apt install ddcutil i2c-tools
   sudo modprobe i2c-dev

2. Download and extract MultiDisplayVCPServer_Linux_x64_v2.0.0.tar.gz:

   tar -xzf MultiDisplayVCPServer_Linux_x64_v2.0.0.tar.gz

3. Run the automated installer:

   chmod +x install.sh && sudo ./install.sh

   (Installs binary to /usr/local/bin, configures I2C group permissions, and installs/starts the multidisplayvcp.service systemd unit).

macOS (Apple Silicon & Intel)

Note

MacBook Displays: Apple locks down built-in MacBook laptop displays, so they cannot be controlled via DDC/CI. However, any external monitor plugged into your Mac (HDMI, USB-C, DisplayPort) works seamlessly. Ensure DDC/CI is enabled in your monitor's on-screen hardware menu!

1. Install prerequisite:

   brew install ddcctl

2. Download and extract MultiDisplayVCPServer_macOS_<arch>_v2.0.0.tar.gz (choose arm64 for Apple Silicon M1/M2/M3/M4 or x64 for Intel):

   tar -xzf MultiDisplayVCPServer_macOS_<arch>_v2.0.0.tar.gz

3. Run the automated installer:

   chmod +x install.sh && ./install.sh

   (Installs the self-contained standalone binary to /usr/local/bin and registers/loads the com.multidisplayvcp.server background LaunchAgent).

4. Verify your monitors:

   /usr/local/bin/MultiDisplayVCPServer.Mac --scan

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⚙️ Configuration (macOS & Linux)

The Windows edition provides a system tray and graphical window to configure settings. Because macOS and Linux run as headless background daemons, their settings are stored in a standard server.json file.

Configuration Locations

• macOS: ~/Library/Application Support/MultiDisplayVCP/server.json
• Linux: /etc/multidisplayvcp/server.json

Configuration Format

{
  "port": 5001,
  "grpcPort": 5002,
  "password": "changeme"
}

(Default password is changeme if unconfigured).

Applying Changes

After editing server.json, reload the background service:

• macOS:

  launchctl unload ~/Library/LaunchAgents/com.multidisplayvcp.server.plist
  launchctl load -w ~/Library/LaunchAgents/com.multidisplayvcp.server.plist

• Linux:

  sudo systemctl restart multidisplayvcp

CLI Overrides & Environment Variables

You can also customize settings without a file:

• Command Line Flags: --password <secret>, --port <num>, --grpc-port <num>, --config <path>
• Environment Variables: VCP_PASSWORD, VCP_PORT, VCP_GRPC_PORT

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🔌 Open Protocol Specification

Any client can control displays via the TCP port using simple HMAC-SHA256 authenticated commands:

• Ping: PING|<timestamp>|<base64_hmac>
• Get Capabilities: GET_CAPS|<timestamp>|<base64_hmac>
• Set VCP Feature: SET_VCP|<timestamp>|<base64_hmac>|<monitor_id>|<vcp_hex_code>|<value>

Where <base64_hmac> is HMAC-SHA256(command + timestamp, password).

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🛠️ Building from Source

Requires the .NET 10.0 SDK:

# Build Windows version
dotnet publish MultiDisplayVCPServer.csproj -c Release

# Build Linux version
dotnet publish Linux/MultiDisplayVCPServer.Linux.csproj -c Release -r linux-x64

# Build macOS version
dotnet publish Mac/MultiDisplayVCPServer.Mac.csproj -c Release -r osx-arm64

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📄 License

MIT License. See LICENSE.txt for details.