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This guide will walk you through sharing a file between two peers in just a few minutes.

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Prerequisites

Before you begin, make sure you have:
  • Node.js v22 or higher installed
  • The p2p-file-share repository cloned
  • A test file to share (or create one)

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Quick Setup

1

Create a test file

First, create a test file to share between peers:
echo "Hello from P2P File Share!" > test.txt
Or use any existing file you want to share.
2

Start the seed node

In your first terminal, start a seed node that has the complete file:
npm start -- --port 6881 --file test.txt
You should see output like:
Nodo P2P iniciado. ID: ab12cd34ef56, escuchando en puerto 6881.
Archivo disponible para compartir: "test.txt" (27 bytes). Esperando conexiones de pares...
The seed node calculates the SHA-1 hash of the file automatically. This hash will be used to verify file integrity after download.
3

Start the leecher node

In a second terminal, start a leecher node that will download the file:
npm start -- --port 6882 --file test-downloaded.txt --peer 127.0.0.1:6881
You should see the download progress:
Conectando con peer inicial 127.0.0.1:6881...
Meta de archivo recibida: "test.txt" (27 bytes, 1 piezas). Iniciando descarga...
Pieza 0 recibida (27 bytes). Piezas restantes: 0.
¡Descarga completada! Archivo "test.txt" descargado completamente.
Verificación de integridad: OK (hash coincide).
El nodo continuará corriendo como seed para compartir el archivo con otros peers.
Once the download completes, the leecher automatically becomes a seed and can share the file with other peers.
4

Verify the downloaded file

Check that the file was downloaded correctly:
cat test-downloaded.txt
The content should match your original file exactly.

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What Just Happened?

Here’s what occurred behind the scenes:
  1. Handshake: The leecher connected to the seed and exchanged metadata (file name, size, hash, piece size)
  2. Bitfield: The seed announced it has all pieces of the file
  3. Request: The leecher requested piece 0
  4. Piece: The seed sent the piece data (encoded in base64)
  5. Verification: The leecher verified the complete file’s SHA-1 hash matches the seed’s hash

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Next Steps

Now that you have a basic P2P network running, try these next:

Add More Peers

Set up a 3+ peer network to see true P2P file distribution

Command Reference

Learn about all available command-line options

Protocol Details

Understand the messaging protocol in depth

Architecture

Learn how the P2P system is designed

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Larger Files

For larger files, you’ll see more detailed progress tracking: 
npm start -- --port 6881 --file large-video.mp4
Seed output: 
Nodo P2P iniciado. ID: ef78cd90ab12, escuchando en puerto 6881.
Archivo disponible para compartir: "large-video.mp4" (157286400 bytes). Esperando conexiones de pares...
Leecher output: 
npm start -- --port 6882 --file downloaded-video.mp4 --peer 127.0.0.1:6881

Conectando con peer inicial 127.0.0.1:6881...
Meta de archivo recibida: "large-video.mp4" (157286400 bytes, 2400 piezas). Iniciando descarga...
Progreso: 10.00% (15728640/157286400 bytes). Velocidad: 1024.5 KB/s
Pieza 0 recibida (65536 bytes). Piezas restantes: 2399.
Pieza 1 recibida (65536 bytes). Piezas restantes: 2398.
...
Progreso: 100.00% (157286400/157286400 bytes). Velocidad: 982.3 KB/s
¡Descarga completada! Archivo "large-video.mp4" descargado completamente.
Verificación de integridad: OK (hash coincide).
Files are automatically split into 64 KiB (65536 bytes) pieces. For files smaller than 64 KiB, the piece size adjusts to match the file size.

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Troubleshooting

If you encounter issues, check out the Troubleshooting guide for common problems and solutions.

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