ScreenSharing

A lightweight Windows screen-sharing and remote-control server. It captures a selected monitor with FFmpeg (gdigrab), encodes it as MPEG-1 video, and streams it over a WebSocket to any browser using JSMpeg. Authenticated browser clients can also send mouse and keyboard input back to the host, which replays it via the Win32 SendInput API.

Features

• Screen capture of any detected monitor via FFmpeg's gdigrab input device
• Real-time MPEG-TS/MPEG-1 video streaming to a browser (no plugins, via JSMpeg)
• Simple built-in HTTP server for serving the web client (index.html, jsmpeg.min.js, app.ico)
• WebSocket-based control channel for remote mouse movement, clicks, scroll, and keyboard input
• Username/password login with a per-session token to authorize the video stream
• Cross-platform build target (Win32 / x64, Debug / Release) via Visual Studio

Project Structure

ScreenSharing/
├── ScreenSharing.slnx           # Visual Studio solution
├── ScreenSharing.vcxproj        # Project file
├── ScreenSharing.vcxproj.filters
├── ScreenSharing.vcxproj.user
├── main.cpp                     # Server: capture, encode, WebSocket, input injection
├── json.hpp                     # nlohmann/json (single header)
├── index.html                   # Web client (login + video canvas)
├── jsmpeg_min.js                # JSMpeg player (rename to jsmpeg.min.js, see below)
├── app.ico                      # Favicon served at /app.ico
└── auth.json                    # Login credentials (see Configuration)

Requirements

• Windows 10/11
• Visual Studio 2022 (or newer) with the "Desktop development with C++" workload
  • Platform toolset v145, C++20 language standard
• Third-party libraries, expected at ../libs/ relative to the project directory:
  • FFmpeg 6.1 (dev libs + headers) → ../libs/ffmpeg-6.1/include, ../libs/ffmpeg-6.1/lib
  • websocketpp → ../libs/websocketpp
  • Asio 1.36.0 (standalone, header-only) → ../libs/asio-1.36.0/include
  • Boost 1.81.0 → ../libs/boost-1.81.0/include

Adjust the AdditionalIncludeDirectories / AdditionalLibraryDirectories in the project's x64 configurations if your libraries live elsewhere.

Note: the include/library paths in the .vcxproj are currently only defined for the x64 configurations. Build with platform x64 (Debug or Release); the Win32 configurations will need the same paths added before they'll compile.

The following FFmpeg import libraries are linked: avcodec, avdevice, avfilter, avformat, avutil, postproc, swresample, swscale. The matching FFmpeg DLLs must be available at runtime (either next to the .exe or on PATH).

Building

1. Place the third-party libraries under ../libs/ as described above (one directory above the project folder).
2. Open ScreenSharing.slnx in Visual Studio.
3. Select the x64 platform and Debug or Release configuration.
4. Build the solution.
5. Copy the following files into the output directory next to ScreenSharing.exe if they aren't already there:
   • index.html
   • jsmpeg_min.js renamed to jsmpeg.min.js (the server and index.html both request /jsmpeg.min.js)
   • app.ico
   • auth.json
   • The FFmpeg runtime DLLs matching your FFmpeg 6.1 build

Configuration

Login credentials are read from auth.json, which must sit next to the executable:

{
  "user": "admin",
  "pass": "123"
}

If the file is missing or fails to parse, the server starts with empty credentials and a warning is printed to the console. Change these credentials before using this on anything but a local test.

Usage

1. Run ScreenSharing.exe.
2. The program lists detected monitors and their resolutions/offsets. Enter the index of the monitor you want to share.
3. The server starts listening on port 9002.
4. From a browser (on the same machine or another PC on the network), navigate to:

   http://<host-ip>:9002
   

5. Log in with the credentials from auth.json.
6. On success, the video stream starts and the canvas becomes the input surface:
   • Mouse movement, clicks, and scroll wheel are forwarded to the host
   • Keyboard input is forwarded while the canvas has focus
7. Press ESC in the server's console window to shut it down.

How It Works

• Capture/Encode pipeline: gdigrab captures the selected monitor region at 30 fps → decoded → scaled with swscale → re-encoded as MPEG-1 video → muxed into an MPEG-TS stream in memory (via a custom AVIOContext write callback) → broadcast as binary WebSocket frames to all authenticated video clients.
• Control channel: every WebSocket connection to any path other than /video is treated as a control connection. It starts unauthenticated and must send {"type":"login","user":...,"pass":...}. On success, the server generates a random session token and returns it; the client then opens a second WebSocket to /video?token=<token> to receive the video stream. Once a control connection is logged in, it may send mousemove, mousedown, mouseup, wheel, keydown, and keyup messages, which are translated into SendInput calls on the host.
• HTTP server: a minimal handler serves / (index.html), /jsmpeg.min.js, and /app.ico from the working directory; anything else returns 404.

Security Notes

This project is intended for use on a trusted local network (e.g., controlling your own PC from another device at home). Be aware of the following before exposing it more broadly:

• Credentials are stored in plain text in auth.json.
• The WebSocket and HTTP traffic is unencrypted (ws://, not wss://), so credentials, the session token, the video stream, and input events are all visible to anyone who can observe the network.
• There's no rate limiting or lockout on login attempts, no HTTPS/TLS, and the session token does not expire.
• Anyone who obtains a valid token can view the screen and inject arbitrary mouse/keyboard input.

Do not expose port 9002 directly to the internet without adding TLS, stronger authentication, and rate limiting.

Dependencies / Credits

• FFmpeg — screen capture, video decoding/encoding, muxing
• websocketpp — WebSocket server
• Asio — networking (used standalone by websocketpp)
• nlohmann/json — JSON parsing (json.hpp)
• JSMpeg — browser-side MPEG-1/TS video player

License

This project is licensed under the MIT License.