LAN File Drop

A safe, boring LAN-only file transfer app for trusted devices — no cloud, no SMB, no admin rights, no credentials.

Send a file from one Windows PC to another on the same local network: the sender selects files and prepares a checksummed manifest, the receiver must explicitly click Accept before anything is written to disk, and every received file is verified against its SHA-256 checksum. Built in C# / .NET with a strict Core / Networking / UI separation and unit-tested transfer logic.

MVP status: Working technical MVP for manual peer transfer. The full send/receive flow has been validated in a manual two-PC smoke test on a real local network (manual IP + port, no discovery) — see docs/manual-smoke.md. There is still no LAN discovery, no packaging/release flow, no automated UI or two-PC tests, and no production-readiness claim.

Screenshots

Manual two-PC smoke test, sender and receiver on separate Windows PCs on the same LAN. Screenshots are redacted copies; private IPs and machine-specific details are masked.

Sender ready with prepared manifest	Receiver waiting for Accept
Receive completed after Accept	Received file in destination folder

Safety

This project is designed to be boring on purpose. It intentionally avoids anything that touches system-level trust, credentials, or remote execution.

• No admin rights required
• No SMB / Windows network shares
• No PowerShell Remoting
• No credentials or accounts
• No WLAN key / Windows key / password access
• No command execution or remote shell
• Local network only, manual peer addressing only (no discovery, DNS, broadcast, or multicast)
• Receiver confirmation required before any file is written
• User-selected files only
• Networking path validates destination names, prevents silent overwrite, and verifies checksums

See docs/security.md for the full safety model.

What Works Now

• Core domain models for transfer requests, peers, and manifests, with SHA-256 checksum and transfer manifest logic
• Manual peer endpoint validation in Core; the UI stores only validated endpoints and never passes raw text to Networking
• Explicit, bounded Probe connection action (probe-only, no transfer)
• File picker preview showing selected file names and sizes only — no full local paths, no content reads during selection
• Explicit Prepare manifest step that computes SHA-256 checksums for the selected files without sending anything
• Hardened manual peer sender/receiver path in Networking: explicit receiver confirmation, reject-without-write, temp-file staging with checksum verification before promotion, all-or-nothing multi-file promotion, and no silent overwrite
• Controlled App wire-up: explicit receive-folder selection, one-shot receiver start on a chosen port, incoming-request confirmation with Accept/Reject, and a separate explicit Send prepared transfer action
• Validated end-to-end in a manual two-PC smoke test on a real local network (docs/manual-smoke.md)
• Automated unit and loopback test coverage for Core and Networking

Known Limitations

• No LAN discovery — peers are addressed manually by IP and port
• No installer, packaging, or release artifacts; run from source
• No automated UI tests and no automated two-PC tests (two-PC validation is a deliberate manual smoke test)
• The receiver is one-shot per start; it does not loop or auto-restart
• UI is a technical MVP, not consumer-polished; for example, the transfer log still shows a static sample entry (known polish item)
• No transport encryption; intended for trusted devices on a trusted local network only
• Not production-ready and not claimed to be

Quick Start

Requires the .NET 10 SDK. No installer exists; run from source:

# build and run tests
dotnet test

# run the desktop app
dotnet run --project src/LanFileDrop.App

For a two-PC transfer, start the app on both machines, pick a receive folder and start the receiver on one, then validate the other machine's IP and port manually on the sender and follow the explicit prepare/send steps. The receiver must accept before any file is written. See docs/manual-smoke.md for the exact validated flow.

Non-Goals

• No cloud sync or internet/WAN transfer
• No NAS or general-purpose file server replacement
• No Windows network shares (SMB) integration
• No user accounts, authentication, or credential storage
• No command execution, scripting, or remote shell capability
• No silent/background transfers — every transfer requires explicit receiver confirmation

Architecture Overview

The solution is split so that the transfer logic can be tested independently of any UI or networking transport:

• LanFileDrop.Core — domain models, transfer manifest, checksum/integrity logic. No UI, no sockets.
• LanFileDrop.Networking — manual peer transport, built on top of Core's domain types. LAN discovery remains unimplemented.
• LanFileDrop.App — Avalonia desktop UI, wires Core and Networking together.
• Tests — one test project per library (LanFileDrop.Core.Tests, LanFileDrop.Networking.Tests).

See docs/architecture.md for details.

Development Stack

• C# / .NET 10 (net10.0)
• Avalonia UI for the desktop GUI
• xUnit for tests
• Windows portable MVP first; cross-platform potential later via Avalonia

Roadmap

• Batch 0 — repo scaffold, solution, docs ✅
• Batch 1 — core domain models + tests ✅
• Batch 2 — transfer manifest / checksum logic + tests ✅
• Batch 3 — local loopback transfer prototype ✅
• Batch 4 — minimal Avalonia UI shell ✅
• Batch 5A–5G — manual peer validation, safety contract, and bounded probe (Core, Networking, UI) ✅
• Batch 6A–6C — file picker preview and hardening ✅
• Batch 7A — send readiness UI skeleton ✅
• Batch 8A — outgoing transfer draft and receiver confirmation skeleton ✅
• Batch 9A — explicit checksum and manifest preparation ✅
• Batch 10A — local manual peer transfer path in Networking with receiver confirmation ✅
• Batch 11A — controlled App wire-up for manual peer transfer, no discovery ✅
• Batch 12A — manual two-PC smoke test performed and documented ✅
• Later — UI polish, LAN discovery, packaging/release, and production-readiness hardening

Documentation

• docs/project-charter.md — goal, target users, non-goals, portfolio intent
• docs/architecture.md — project separation and responsibilities
• docs/security.md — safety model in detail
• docs/test-plan.md — testing approach across batches
• docs/manual-smoke.md — manual two-PC smoke test record

License

MIT — see LICENSE.