EntglDb.Services.FileTransfer 2.3.0

EntglDb.Services.FileTransfer

Peer-to-peer file transfer service for the EntglDb mesh network.
Allows any node to query metadata and stream file downloads from remote peers over the shared TCP connection, with automatic SHA-256 integrity verification.

What's Included

• IFileProvider — server-side abstraction you implement to control which files are exposed (prevents path traversal)
• FileQueryHandler — responds to file-metadata queries (wire type 1100)
• FileDownloadHandler — streams file chunks to the requesting peer (wire type 1102), with SHA-256 hash computed on the fly
• IFileTransferService — client-side API with QueryAsync and DownloadAsync
• FileTransferIntegrityException — thrown if the received data does not match the server's checksum

Installation

dotnet add package EntglDb.Core
dotnet add package EntglDb.Network
dotnet add package EntglDb.Services.FileTransfer

Quick Start

1 — Implement IFileProvider (server side)

public class ReportFileProvider : IFileProvider
{
    private static readonly Dictionary<string, string> _catalogue = new()
    {
        ["report-q1"] = "/data/reports/q1-2026.pdf",
        ["report-q2"] = "/data/reports/q2-2026.pdf",
    };

    public Task<FileTransferInfo?> GetInfoAsync(string fileId, CancellationToken ct)
    {
        if (!_catalogue.TryGetValue(fileId, out var path) || !File.Exists(path))
            return Task.FromResult<FileTransferInfo?>(null);

        var fi = new System.IO.FileInfo(path);
        return Task.FromResult<FileTransferInfo?>(new FileTransferInfo
        {
            FileId    = fileId,
            FileName  = fi.Name,
            SizeBytes = fi.Length,
        });
    }

    public Task<Stream?> OpenReadAsync(string fileId, CancellationToken ct)
    {
        if (!_catalogue.TryGetValue(fileId, out var path) || !File.Exists(path))
            return Task.FromResult<Stream?>(null);

        return Task.FromResult<Stream?>(File.OpenRead(path));
    }
}

2 — Register services

builder.Services
    .AddEntglDbNetwork<MyConfigProvider>()
    .AddEntglDbFileTransfer();                    // registers handlers + IFileTransferService

builder.Services.AddSingleton<IFileProvider, ReportFileProvider>();

3 — Download a file from a peer

public class MyService
{
    private readonly IFileTransferService _fileTransfer;
    public MyService(IFileTransferService fileTransfer) => _fileTransfer = fileTransfer;

    public async Task DownloadReportAsync(string peerAddress, CancellationToken ct)
    {
        // Check it exists first
        var info = await _fileTransfer.QueryAsync(peerAddress, "report-q1", ct);
        if (info is null) { Console.WriteLine("File not found on peer."); return; }

        Console.WriteLine($"Downloading {info.FileName} ({info.SizeBytes:N0} bytes)...");

        using var fs = File.OpenWrite("report-q1.pdf");
        await _fileTransfer.DownloadAsync(peerAddress, "report-q1", fs, ct);

        Console.WriteLine("Done. SHA-256 verified.");
    }
}

Wire Protocol

Documentation

• Full README
• Custom P2P Services
• Message Type Ranges