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LanShare — P2P LAN File Transfer

LAN Share is a fast, open-source file sharing application that lets you transfer files between devices on the same local network — without internet, cloud services, or external servers. Built with C++ and Qt, it enables secure, peer-to-peer file transfers with minimal setup, making it ideal for quick sharing across laptops, desktops, and local environments.

No files ever touch the signaling server — they transfer peer-to-peer.

Architecture

Device A ──WebSocket──► Signaling Server ◄──WebSocket── Device B
Device A ◄────────────── WebRTC P2P DataChannel ──────────────► Device B
                          (actual file bytes)

The signaling server only exchanges WebRTC handshake messages (offer/answer/ICE candidates).

How It Works

Step Description
1 Both clients connect to the WebSocket signaling server
2 Server assigns each peer a UUID and broadcasts the peer list
3 Sender creates an RTCPeerConnection + DataChannel and sends an SDP offer via the signaling server
4 Receiver replies with an SDP answer
5 ICE candidates are exchanged to establish the direct path
6 DataChannel opens — file is chunked (64 KB pieces) and sent as ArrayBuffer
7 Receiver reassembles chunks into a Blob and triggers a browser download

Notes

  • Works on LAN (same Wi-Fi or Ethernet) and Bluetooth PAN
  • STUN servers (Google) are used for ICE — no TURN server configured, so devices must be on the same network
  • Multiple simultaneous transfers are supported
  • No size limit beyond your browser's memory for the receiver-side reassembly

Tech Stack

  • Frontend: React 18 + Vite + WebRTC (RTCPeerConnection, RTCDataChannel)
  • Signaling Server: Node.js + ws (WebSocket library)
  • Discovery: Signaling server broadcasts connected peer list
  • Transfer: Direct WebRTC DataChannel, chunked ArrayBuffer streaming