protected async UniTask HandshakeAsync(int bits)
{
// in the very first message we must mine a hashcash token
// and send that as a hello
// the server won't accept connections otherwise
string applicationName = Application.productName;
HashCash token = await UniTask.RunOnThreadPool(() => HashCash.Mine(applicationName, bits));
byte[] hello = new byte[1000];
int length = HashCashEncoding.Encode(hello, 0, token);
var data = new ArraySegment <byte>(hello, 0, length);
// send a greeting and see if the server replies
await SendAsync(data);
var stream = new MemoryStream();
try
{
await ReceiveAsync(stream);
}
catch (Exception e)
{
throw new InvalidDataException("Unable to establish connection, no Handshake message received.", e);
}
}
private bool Validate(byte[] data, int msgLength)
{
// do we have enough data in the buffer for a HashCash token?
if (msgLength < Kcp.OVERHEAD + KcpConnection.RESERVED + HashCashEncoding.SIZE)
{
return(false);
}
// read the token
HashCash token = HashCashEncoding.Decode(data, Kcp.OVERHEAD + KcpConnection.RESERVED);
RemoveExpiredTokens();
// have this token been used?
if (used.Contains(token))
{
return(false);
}
// does the token validate?
if (!token.Validate(Application.productName, HashCashBits))
{
return(false);
}
used.Add(token);
expireQueue.Enqueue(token);
// brand new token, and it is for this app, go on
return(true);
}
// calculate the hash of a hashcash token
private byte[] Hash(HashAlgorithm hashAlgorithm, byte[] buffer)
{
int length = HashCashEncoding.Encode(buffer, 0, this);
return(hashAlgorithm.ComputeHash(buffer, 0, length));
}
