OpenKVM

DIY KVM device for remote-controlling a computer. KVM stands for Keyboard & Video & Mouse.

A side system on a rackmount server, IPMI in Dell Server for example.

Unlike an IP-KVM, this project respects VNC protocol.

Just like the MIT license says, no warranty or guarantee.

And do NOT use for any illegal purposes.

TODO

• Installation script
  • Register as a system service
  • Start on boot
• VNC authentication
  • DES encryption in Golang can NOT directly apply to VNC Authentication
• More effective to calculate the difference between frames
  • Balance between the power of SBC and the network efficiency
  • Or achieve more support for noVNC, beyond rfc6143
• Device filter for USB devices: for multiple device controlling
• OTG as keyboard and mouse, see Linux USB Gadget API
• Using a single command to get the frame for Video, like

  v4l2-ctl --device=/dev/video0 --stream-mmap --stream-count=1 --stream-to=- --set-fmt-video="width=640,height=480,pixelformat=MJPG"

Dev Environment

Hardware

NONE of them is sponsored, use them at your own risk!

Essential hardware are:

• A computer that can run Golang
  • An old computer
  • SBC
    • RaspberryPi
    • OrangePi
    • BTT-Pi
    • etc...
  • Maybe an Android phone?
• HDMI Recorder
  • The common seen HDMI Recorder is a USB 3.0 device.
    There is only blank data from the HDMI Recorder on a USB 2.0 port.
    It seems that this is the problem of the HDMI Recorder itself,
    the HDMI Recorder I bought can NOT work on Linux (Debian ARM or Ubuntu 24.04) even with a USB 3.0 port.
    Then, on the selection of SBC, beware of the support of USB 3.0.
    • This should be the problem with HDMI recorder itself of the driver in Linux,
      I am lack of the knowledge of the driver in Linux, but I might find a solution for it:

      # Display all USB device, make sure the HDMI recorder is in 480M or above
      lsusb -t
      # /:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
      #     |__ Port 1: Dev 3, If 0, Class=Video, Driver=uvcvideo, 480M
      #     |__ Port 1: Dev 3, If 1, Class=Video, Driver=uvcvideo, 480M
      #     |__ Port 1: Dev 3, If 2, Class=Audio, Driver=snd-usb-audio, 480M
      #     |__ Port 1: Dev 3, If 3, Class=Audio, Driver=snd-usb-audio, 480M
      
      # Get the id of the USB device
      lsusb
      # Bus 001 Device 003: ID 1de1:f105 Actions Microelectronics Co. Hagibis
      
      # Reset the USB device
      # Replace this with the id or the name of your USB device. 
      # For me, this is `Hagibis` or `1de1:f105`
      usbreset Hagibis
      
      # Capture one frame from device
      v4l2-ctl --verbose \
      --device=/dev/video0 \
      --stream-mmap \
      --stream-count=1 \
      --stream-to=frame.jpg \
      --set-fmt-video="width=640,height=480,pixelformat=MJPG"
      
      # BUT! But, in size of 1920x1080, frame will be corrupted
      
      # Without resetting the USB device, there will be some error message in `dmesg` command
      # Non-zero status (-71) in video completion handler.
      
      # Here are some helpful commands
      # List all video devices
      v4l2-ctl --list-devices
      # List all supported formats for a video device
      v4l2-ctl --list-formats -d [device name or path or index] # v4l2-ctl --list-formats -d 0
      # List all supported frame sizes
      v4l2-ctl --list-framesizes [pixel format] -d [device] # v4l2-ctl --list-framesizes MJPEG -d 0

  • Or a webcam with an always-on monitor.
    • I know...this is a stupid way -- pointing a camera to a screen.
• Keyboard & Mouse Emulator
  • ESP32-S3
  • ESP32-S2
  • Arduino?
  • Some other device that supports USB HID output.
    • HID over BLE is not recommended, because it may not work in BIOS.
• Relay and/or delayed relay

My Gears

• SBC: OrangePi 3 LTS
  • ¥241 RMB ≈ $34 USD
• HDMI Recorder: hagibis UHC07
  • ¥69 RMB ≈ $10 USD
  • ⚠️ This device ONLY supports 1920x1080 and 3840x2160.
• Keyboard & Mouse: ESP32-S3
  • I bought a third-party one of WeAct ESP32 S3 (A) DevKitC 1.
  • ¥52 RMB ≈ $7.5 USD
• 5V relay * 2, 5V delayed relay * 1
  • ¥15 RMB ≈ $2 USD

Others

• Test Device:
  • RaspberryPi 2B
  • A Windows computer
  • Ubuntu 24.04 x86_64
• Some SD cards.
• Some USB Type-C2C/C2A cables.
• A HDMI cable.
• Some power supplies.

It costs about ¥300 RMB ≈ 40 USD.

Price is for reference only, the actual price may vary.

Software

• GO
• OpenCV
• PlatformIO
• noVNC

Diagram

飞书文档, FeiShu Doc

Run

Debian ARM64

1. Install GO dev kit

   sudo apt-get update
   sudo apt-get install -y wget curl ffmpeg v4l-utils
   GO_ZIP="go1.22.3.linux-arm64.tar.gz"
   wget "https://go.dev/dl/$GO_ZIP"
   sudo rm -rf /usr/local/go && sudo tar -C /usr/local -xzf "$GO_ZIP"

2. Pull this repo

   sudo apt-get update
   sudo apt-get install -y git
   git clone https://github.com/allape/openkvm.git

3. Install OpenCV
   • Method 1: Install from APT

     sudo apt-get update
     sudo apt-get install -y build-essential g++ cmake pkg-config unzip libopencv-dev
     
     # But in BTT-Pi, it is only up tp v4.5.1
     # Then, I have to change the version of `gocv.io/x/gocv` to corresponding version
     sed -i 's/gocv.io\/x\/gocv v0.36.1/gocv.io\/x\/gocv opencv-4.5.1/g' openkvm/go.mod

   • Method 2: Build OpenCV from source
     This may cost over 10 hours to build on BTT-Pi, I crashed at 96% :(
     https://docs.opencv.org/4.x/d7/d9f/tutorial_linux_install.html

     mkdir opencv4 && cd opencv4
     wget -O opencv.zip https://github.com/opencv/opencv/archive/4.x.zip
     unzip opencv.zip
     mkdir -p build && cd build
     cmake ../opencv-4.x
     cmake --build .

4. Get noNVC

   git clone --depth 1 https://github.com/novnc/noVNC.git
   
   # [Optional] You can run noVNC separately
   python3 -m http.server --directory noVNC/ 8081

5. Flash ESP32-S3
   • PIO: Espressif has dropped the support for PIO in ESP-IDF v5.x. See git log to retrieve the code.
     • Open folder km/esp32s3 of this project in VSCode
     • After installing PlatformIO extension
       • Go to PlatformIO Tab
       • PROJECT TASKS -> Default -> General -> Upload
       • Or open command palette and type PlatformIO: Upload
         • ⌘ + shift + p on macOS to open command palette
         • ctrl + shift + p on Windows or Ubuntu
   • Arduino
     • Open Perferences -> Additional Board Manager URLs -> Add https://espressif.github.io/arduino-esp32/package_esp32_dev_index.json
       • Click HERE for more details
     • Open km/esp32s3-arduino/main/main.ino with Arduino IDE
     • Select board ESP32S3 Dev Module and corresponding port
     • Click Upload
6. Run or build repo

   cd openkvm
   cp kvm.toml.tpl kvm.toml
   
   # Find out serial port
   dmesg | grep tty
   
   # Edit this file to apply your settings
   vim kvm.toml 
   
   # Should run with super user privilege
   sudo go run .

7. Open browser and go to http://ip:8080/vnc.html, then click Connect
   • Hostname and port may vary depending on your settings

Credits

• Listed in go.mod
• Roboto Font
• noVNC
• PlatformIO
• ESP-IDF
• ESP32-Arduino
• Raspberry Pi Imager
• KeyMap