Peer Wire Protocol

peer-wire-protocol is a node stream implementation of the peer wire protocol specification. The protocol is the main communication layer when transferring files using BitTorrent and is used by peerflix.

It is available through npm:

npm install peer-wire-protocol

Usage is simple

Since the protocol is implemented as a stream all you have to do is pipe some to and from it

var pwp = require('peer-wire-protocol');
var net = require('net');
 
net.createServer(function(socket) {
    var wire = pwp();
 
    // pipe to and from the protocol
    socket.pipe(wire).pipe(socket);
 
    wire.on('handshake', function(infoHash, peerId) {
        // lets emit a handshake of our own as well
        wire.handshake(Buffer.from('my info hash'), Buffer.from('my peer id'));
    });
 
    wire.on('unchoke', function() {
        console.log('peer is no longer choking us: '+wire.peerChoking);
    });
}).listen(6881);

Full API

Handshaking

Send and receive a handshake from the peer. This is the first message.

// send a handshake to the peer
wire.handshake(infoHash, peerId, {dht:true});
wire.on('handshake', function(infoHash, peerId, extensions) {
    // receive a handshake
});

Both the infoHash and the peerId should be 20 bytes

Choking

Check if you or the peer is choking

wire.peerChoking; // is the peer choking us?
wire.amChoking; // are we choking the peer?
 
wire.on('choke', function() {
    // the peer is now choking us
});
wire.on('unchoke', function() {
    // peer is no longer choking us
});

Interested

See if you or the peer is interested

wire.peerInterested; // is the peer interested in us?
wire.amInterested; // are we interested in the peer?
 
wire.on('interested', function() {
    // peer is now interested
});
wire.on('uninterested', function() {
    // peer is no longer interested
});

Bitfield

Exchange piece information with the peer

// send a bitfield to the peer
wire.bitfield(buffer);
wire.on('bitfield', function(bitfield) {
    // bitfield received from the peer
});
 
// send a have message indicating that you have a piece
wire.have(pieceIndex);
wire.on('have', function(pieceIndex) {
    // peer has sent you a have message
});

You can always see which pieces the peer have

wire.peerPieces[i]; // returns true if peer has piece i

Requests

Send and respond to requests for pieces

// request a piece from a peer
wire.request(pieceIndex, offset, length, function(err, block) {
    if (err) {
        // there was an error (peer has started choking us etc)
        return;
    }
    // got piece
});
 
// cancel a request to a peer
wire.cancel(pieceIndex, offset, length);
 
// receive a request from a peer
wire.on('request', function(pieceIndex, offset, length, callback) {
    // ... read piece ...
    callback(null, piece); // respond back to the peer
});
 
wire.requests;     // list of requests we currently have pending {piece, offset, length}
wire.peerRequests; // list of requests the peer currently have pending {piece, offset, length}

You can set a request timeout if you want to

wire.setTimeout(5000); // head request should take a most 5s to finish

If the timeout is triggered the request callback is called with an error and a timeout event is emitted.

DHT and port

You can set the extensions flag dht in the handshake to true if you participate in the torrent dht. Afterwards you can send your dht port

// send your port to the peer
wire.port(dhtPort);
wire.on('port', function(dhtPort) {
    // peer has sent a port to us
});

Keep-Alive

You can enable the keep-alive ping (triggered every 60s)

// starts the keep alive
wire.setKeepAlive(true);
wire.on('keep-alive', function() {
    // peer sent a keep alive - just ignore it
});

Transfer stats

Check how many bytes you have uploaded and download

wire.uploaded; // number of bytes uploaded
wire.downloaded; // number of bytes downloaded
 
wire.on('download', function(numberOfBytes) {
    ...
});
wire.on('upload', function(numberOfBytes) {
    ...
});

License

MIT