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Overview

The P2P file sharing application is started using the peer.js entry point with command-line arguments.

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Basic Syntax

node src/peer.js --port <puerto> --file <rutaArchivo> [--peer <host:puerto>]

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Required Parameters

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--port
integer
required
The TCP port number on which this node will listen for incoming connections.Validation: Must be a valid integer between 1 and 65535.Example:
node src/peer.js --port 6881 --file video.mkv
The port is parsed as an integer in src/peer.js:19:
port = parseInt(args[i+1], 10);
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--file
string
required
The file path for this node.
  • For seeds: Path to an existing file to share
  • For leechers: Path where the downloaded file will be saved
Validation: The path can be absolute or relative. For seeds, the file must exist. For leechers, the file will be created.Examples:
# Absolute path
node src/peer.js --port 6881 --file "/home/user/videos/movie.mkv"

# Relative path
node src/peer.js --port 6881 --file "./downloads/file.pdf"
The file path is read in src/peer.js:22:
filePath = args[i+1];

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Optional Parameters

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--peer
string
Initial peer to connect to in the format host:port. This is used by leechers to connect to their first seed or peer.Format: <host>:<port> where:
  • host can be an IP address (e.g., 192.168.1.100) or hostname (e.g., localhost, 127.0.0.1)
  • port must be a valid port number
Default: If not specified, the node will only accept incoming connections and wait for other peers to connect.Examples:
# Connect to local seed
node src/peer.js --port 6882 --file output.mkv --peer 127.0.0.1:6881

# Connect to remote peer
node src/peer.js --port 6883 --file file.zip --peer 192.168.1.50:6881
The peer address is parsed in src/peer.js:39-50:
if (peerAddress) {
    const sepIndex = peerAddress.lastIndexOf(':');
    if (sepIndex === -1) {
        console.error('Formato de --peer inválido. Use host:puerto');
        process.exit(1);
    }
    peerHost = peerAddress.substring(0, sepIndex);
    peerPort = parseInt(peerAddress.substring(sepIndex+1), 10);
    if (!peerPort) {
        console.error('Formato de --peer inválido. Puerto no válido.');
        process.exit(1);
    }
}
For leechers without an initial peer, the node will print a warning:
Advertencia: Este nodo no tiene el archivo y ningún peer inicial fue proporcionado. 
El nodo esperará a que algún seed se conecte.

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Validation Rules

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Required Arguments

Both --port and --file are required. If either is missing, the program displays usage information and exits: 
// From src/peer.js:34
if (!port || !filePath) printUsageAndExit();

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Invalid Arguments

If any unrecognized argument is provided, the program exits with usage information: 
// From src/peer.js:28-30
else {
    // argumento erroneo
    printUsageAndExit();
}

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Peer Format Validation

The --peer parameter must follow the host:port format:
  • Must contain a colon (:) separator
  • Port must be a valid integer
  • If validation fails, the program exits with an error message

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Usage Examples

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Starting a Seed Node

# Share a file on port 6881
node src/peer.js --port 6881 --file "/path/to/file.ext"
Expected output: 
Nodo P2P iniciado. ID: ab12cd34ef56, escuchando en puerto 6881.
Archivo disponible para compartir: "file.ext" (1048576 bytes). Esperando conexiones de pares...

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Starting a Leecher Node

# Download a file from a seed at 127.0.0.1:6881
node src/peer.js --port 6882 --file "/path/to/output.ext" --peer 127.0.0.1:6881
Expected output: 
Conectando con peer inicial 127.0.0.1:6881...
Meta de archivo recibida: "file.ext" (1048576 bytes, 16 piezas). Iniciando descarga...

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Using npm Scripts

The package.json defines convenient npm scripts: 
# Using the seed script
npm run seed -- --port 6881 --file ./my-file.zip
From package.json:6-10: 
"scripts": {
  "start": "node src/peer.js",
  "seed": "node src/peer.js --port 6881 --file ./ruta_al_archivo",
  "leech": "node src/peer.js --port 6882 --file ./ruta_al_archivo --peer <host:puerto>"
}

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Help and Usage Information

To display usage information, run the command without required arguments: 
node src/peer.js
Output: 
Uso: node peer.js --port <puerto> --file <rutaArchivo> [--peer <host:puerto>]
Ejemplo (iniciar seed): node peer.js --port 6881 --file "/ruta/al/archivo.ext"
Ejemplo (iniciar peer leecher): node peer.js --port 6882 --file "/ruta/de/salida.ext" --peer 127.0.0.1:6881
This is defined in src/peer.js:4-9: 
function printUsageAndExit() {
    console.log('Uso: node peer.js --port <puerto> --file <rutaArchivo> [--peer <host:puerto>]');
    console.log('Ejemplo (iniciar seed): node peer.js --port 6881 --file "/ruta/al/archivo.ext"');
    console.log('Ejemplo (iniciar peer leecher): node peer.js --port 6882 --file "/ruta/de/salida.ext" --peer 127.0.0.1:6881');
    process.exit(1);
}

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Error Messages

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Missing Required Arguments

Uso: node peer.js --port <puerto> --file <rutaArchivo> [--peer <host:puerto>]
...
Exits with code 1

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Invalid Peer Format (Missing Colon)

Formato de --peer inválido. Use host:puerto
Exits with code 1

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Invalid Peer Format (Invalid Port)

Formato de --peer inválido. Puerto no válido.
Exits with code 1

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Unrecognized Argument

Uso: node peer.js --port <puerto> --file <rutaArchivo> [--peer <host:puerto>]
...
Exits with code 1

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