lanshare

Send files directly between two devices on the same Wi-Fi network or mobile hotspot. No internet connection, no cloud account, no Bluetooth pairing.

One device starts a receiver and gets a one-time PIN. The other device sends a file to that PIN. That's it. Transfers run over a plain TCP socket at full local network speed and are encrypted end-to-end, so the exchange is fast and private even on a network you don't fully trust.

Why not Bluetooth?

Bluetooth is slow and range-limited. lanshare instead uses whatever Wi-Fi link is already available - a home router, an office network, or one phone's hotspot with the other device connected to it - which is typically 10-50x faster and works at normal Wi-Fi range.

Features

• Wi-Fi or hotspot, no data plan required - works the moment two devices share any local network, including a hotspot with no upstream internet.
• Automatic discovery - senders can find nearby receivers by name instead of typing an IP address.
• End-to-end encryption - every transfer is protected with AES-256-GCM, keyed from a one-time PIN via PBKDF2 (200,000 iterations). The PIN itself never crosses the network.
• Tamper detection - each file is checksummed with SHA-256 before sending and verified again after saving.
• Path-safe by design - incoming filenames are sanitized so a malicious peer can't write outside the destination folder, and existing files are never silently overwritten.
• Concurrent transfers - the receiver handles multiple incoming connections at once, each on its own thread.
• Zero configuration - no accounts, no server, no firewall rules beyond the one port lanshare listens on.
• Simple CLI - three commands: receive, send, discover.

Installation

pip install .

or, from a clone of this repository:

pip install -r requirements.txt
python -m lanshare --help

Requires Python 3.8+. The only runtime dependency is the widely used cryptography library.

Usage

1. On the receiving device

lanshare receive

lanshare receiver running as 'daniels-laptop'
  Listening on : 192.168.1.42:50556
  Saving to    : /home/daniel/received
  PIN          : 483920

Share the PIN with the sender. Press Ctrl+C to stop.

Read that PIN out to whoever is sending you a file (or send it over chat - it's only valid for this session and is useless without also being on the same network).

2. On the sending device

lanshare send vacation_photos.zip

No --host given, searching the network for receivers...
Found daniels-laptop (192.168.1.42:50556)
Enter the PIN shown on the receiving device: 483920
Sending vacation_photos.zip [########################........] 74.2%  186.4 MB/256.0 MB  42.1 MB/s

You can also skip discovery and target a device directly:

lanshare send report.pdf --host 192.168.1.42 --pin 483920

Multiple files in one go:

lanshare send photo1.jpg photo2.jpg notes.txt --host 192.168.1.42

Connecting over a hotspot

If you don't have a shared router, one device can just turn on its mobile hotspot and the other can connect to it as a normal Wi-Fi network - no data plan is consumed for the transfer itself since the file never leaves the local link between the two devices. From there, usage is identical to the examples above.

Finding receivers manually

lanshare discover

Searching for receivers for 3s...
Found 2 receiver(s):
  - daniels-laptop (192.168.1.42:50556)
  - kitchen-tablet (192.168.1.57:50556)

How it works

1. Discovery - the receiver listens for a UDP broadcast asking "who's out there?" and answers with its name and port. This never touches file contents and can be skipped entirely with --host.
2. Handshake - the sender generates a random salt and derives a 256-bit key from the salt and the shared PIN using PBKDF2-HMAC-SHA256. The receiver derives the same key from its own copy of the PIN. If the PINs don't match, the very first decrypted message fails integrity verification and the connection is dropped immediately.
3. Transfer - the file is streamed in 1 MiB chunks, each independently encrypted and authenticated with AES-256-GCM, so partial data can never be tampered with or replayed.
4. Verification - the receiver recomputes the SHA-256 checksum of the saved file and confirms it matches what the sender sent before reporting success.

Security notes

• The PIN is the only shared secret. Treat it like a temporary password - don't post it somewhere public while a transfer is pending.
• Anyone who doesn't know the PIN cannot decrypt a transfer even if they can see the network traffic.
• lanshare only ever binds to the local network; it does not open any connection to the internet.

Command reference

Run lanshare --help or lanshare <command> --help for the full list of options.

Running the tests

pip install pytest
pytest

License

MIT - see LICENSE.