Zender

Simple LAN file-transfer utility using UDP discovery and TCP file transfer.

Zender discovers peers on the local network (UDP broadcast), negotiates a TCP connection, and sends or receives files using a small, interactive console UI and native file/folder choosers.

• src/xender.py — main implementation (discovery, connection, transfer, console UI).
• test/test_xender.py — interactive test/demo for sending/receiving sockets.

• Peer discovery (broadcast / scan).
• TCP-based file transfer with simple framing (filename length, filename, filesize, then file bytes).
• Console menu for scan/broadcast and send/receive flows.
• Cross-platform input handling (Windows msvcrt, Unix select) and Tk filedialog for choosing files/folders.

• Python 3.8+
• Optional: netifaces for better broadcast address detection (pip install netifaces).
• tkinter (usually included with Python on Windows/macOS; install system package on some Linux distributions).

1. (Recommended) Create and activate a virtual environment:

python -m venv .venv
.\\.venv\\Scripts\\Activate.ps1   # Windows PowerShell
# or
.\\.venv\\Scripts\\activate.bat   # Windows cmd
source .venv/bin/activate            # Unix/macOS

2. (Optional) Install netifaces:

pip install netifaces

3. Run the interactive Zender app:

python -m src.Zender
# or
python src/Zender.py

• Main menu: [1] Scan to look for nearby devices, [2] Broadcast to advertise and accept a connection, [3] Exit.
• After connecting, choose [1] Send files to open a file dialog and send one or more files, or [2] Receive files to pick a destination folder and receive incoming files.
• On the console prompts, press q to cancel scans or receives where supported.
• The tool uses a simple framed protocol: command byte (0x01=file), 4-byte filename-length, filename, 8-byte filesize, file bytes.

• The included test/test_xender.py file acts as an interactive demo to create a listening or connecting socket. Run it and follow on-screen prompts:

python -m pytest test/test_xender.py -q

Or run two terminals manually:

• Terminal A (listener):

  python -m src.xender   # choose Broadcast and accept

• Terminal B (sender):

  python -m src.xender   # choose Scan and connect, then Send files

• The code falls back to the broadcast address 255.255.255.255 when netifaces is not available or no broadcast address is found.
• On Windows, console key detection uses msvcrt.kbhit(); on Unix it uses select and reading from stdin.
• The UI uses tkinter.filedialog for file/folder selection — when running headless or in CI, GUI dialogs will block or fail.
• The current transfer protocol is intentionally simple and meant for local, trusted networks — it has no encryption or integrity verification.

PRs and issues welcome. If you add features (e.g., resume, checksums, GUI, encryption), include tests and a short usage example.

Provided for learning and experimentation.