public void InitiateHandshake(byte[] infoHash)
{
logger.LogInformation("Our Peer id: " + Client.peerId.ToHuman());
var fixedHeader = new byte[20];
fixedHeader[0] = (byte)19;
"BitTorrent protocol".ToASCII().CopyTo(fixedHeader, 1);
var bufferBitfield = new byte[8];
bufferBitfield[5] = (byte)16;
Client.extensionsEnabled = true;
TcpClient connection = new TcpClient();
connection.ConnectAsync(peer.Address, peer.Port).Wait();
if (!connection.Connected)
{
throw new Exception("Failed to connect to Peer.");
}
var initialHandshake = new byte[68];
fixedHeader.CopyTo(initialHandshake, 0);
bufferBitfield.CopyTo(initialHandshake, fixedHeader.Length);
infoHash.CopyTo(initialHandshake, fixedHeader.Length + bufferBitfield.Length);
Client.peerId.CopyTo(initialHandshake, fixedHeader.Length + bufferBitfield.Length + infoHash.Length);
logger.LogInformation(LoggingEvents.HANDSHAKE_OUTGOING, "Sending our handshake to " + peer.Address + ":" + peer.Port);
using (var stream = connection.GetStream())
{
stream.Write(initialHandshake);
logger.LogInformation(LoggingEvents.HANDSHAKE_INCOMING, "Received response from Peer.");
var theirFixedHeader = stream.ReadBytes(20);
if (!theirFixedHeader.SequenceEqual(fixedHeader))
{
throw new Exception("Peer failed to return fixed header; aborting connection.");
}
var theirBuffer = stream.ReadBytes(8);
if (theirBuffer[5] == 16)
{
theirExtensionsEnabled = true;
}
var theirInfoHash = stream.ReadBytes(20);
logger.LogInformation(LoggingEvents.HANDSHAKE_INCOMING, "Peer's infohash is: " + theirInfoHash.ToHuman());
if (!theirInfoHash.SequenceEqual(infoHash))
{
throw new Exception("Peer failed to return a matching infohash; aborting connection.");
}
var theirpeerId = stream.ReadBytes(20);
logger.LogInformation(LoggingEvents.HANDSHAKE_INCOMING, "The Peer's ID is " + theirpeerId.ToHuman());
if (Client.extensionsEnabled && theirExtensionsEnabled)
{
var theirExtensionHeader = GetPeerExtensionHeader(stream);
var decodedExtensionHeader = Bencoding.DecodeDict(theirExtensionHeader);
var theirExtensions = decodedExtensionHeader.GetDict("m");
logger.LogInformation(LoggingEvents.EXTENSION_HEADER_IN, "Peer's extension header:" + Environment.NewLine + Bencoding.ToHuman(theirExtensionHeader));
var extensionDict = GenerateExtentionDict();
var extensionHeader = new byte[extensionDict.Length + 6];
var lengthPrefix = (extensionDict.Length + 2).EncodeBytes();
Array.Copy(lengthPrefix, extensionHeader, 4);
extensionHeader[4] = 20;
extensionHeader[5] = 0;
extensionDict.CopyTo(extensionHeader, 6);
stream.Write(extensionHeader);
logger.LogInformation(LoggingEvents.EXTENSION_HEADER_OUT, "Sending our extension header: " + Environment.NewLine + Bencoding.ToHuman(extensionDict));
// Send interested message
stream.Write(1.EncodeBytes());
stream.Write(new byte[1] {
2
});
logger.LogInformation(LoggingEvents.PEER_PROTOCOL_MSG, "Sent interested message.");
if (theirExtensions.ContainsKey("ut_metadata"))
{
logger.LogInformation(LoggingEvents.METADATA_EXCHANGE, "They also support metadata exchange. Lets try that.");
var theirMetadataExtensionId = (byte)theirExtensions.Get("ut_metadata");
var metadataExchange = new MetadataExchange(decodedExtensionHeader.Get("metadata_size"));
try
{
torrent.Metadata = metadataExchange.GetMetadata(stream, connection, 2, theirMetadataExtensionId, infoHash);
} catch (MetadataException e)
{
logger.LogWarning("Unable to get metadata from current peer: ", e);
}
}
}
}
}
private void handleMessage(UDPSocket.ReceivedPacket message)
{
var value = Bencoding.DecodeDict(message.Data);
var type = value.GetString("y");
switch (type)
{
case "r":
{
var key = new QueryKey
{
Token = value.GetBytes("t"),
EP = message.Source
};
if (pendingQueries.ContainsKey(key))
{
var responseSource = pendingQueries[key];
pendingQueries.Remove(key);
responseSource.TrySetResult(value);
}
else
{
logger.LogDebug("Got unexpected response message.");
}
break;
}
case "e":
{
var key = new QueryKey
{
Token = value.GetBytes("t"),
EP = message.Source
};
logger.LogError($"Got error mesage for {key}.");
if (pendingQueries.ContainsKey(key))
{
var responseSource = pendingQueries[key];
pendingQueries.Remove(key);
var errors = value.GetList("e");
var code = (Int64)errors[0];
var errorMessage = ((byte[])errors[1]).FromASCII();
var exception = new Exception($"{code} {errorMessage}");
responseSource.TrySetException(new Exception[] { exception });
}
else
{
logger.LogError($"But I don't even know {key}!");
}
break;
}
case "q":
{
logger.LogDebug($"Ignored query mesage from {message.Source}.");
// do nothing because we're read-only
break;
}
default:
{
logger.LogDebug($"Got unknown mesage from {message.Source}.");
// maybe we could send an error?
break;
}
}
}