protected async virtual Task RequestConnectionAsync(NetworkStream nStream, byte command, string destinationHost, int destinationPort,
CancellationToken cancellationToken = default)
{
var dstIp = await HostHelper.GetIPAddressBytesAsync(destinationHost);
var dstPort = HostHelper.GetPortBytes(destinationPort);
var userId = Array.Empty <byte>();
// Set the credentials if needed
if (Settings.Credentials != null && !string.IsNullOrEmpty(Settings.Credentials.UserName))
{
userId = Encoding.ASCII.GetBytes(Settings.Credentials.UserName);
}
// REQUEST GRANT
// +----+----+----+----+----+----+----+----+----+----+....+----+
// | VN | CD | DSTPORT | DSTIP | USERID |NULL|
// +----+----+----+----+----+----+----+----+----+----+....+----+
// 1 1 2 4 variable 1
var request = new byte[9 + userId.Length];
request[0] = VersionNumber;
request[1] = command;
dstPort.CopyTo(request, 2);
dstIp.CopyTo(request, 4);
userId.CopyTo(request, 8);
request[8 + userId.Length] = 0x00;
await nStream.WriteAsync(request.AsMemory(0, request.Length), cancellationToken).ConfigureAwait(false);
// READ RESPONSE
// +----+----+----+----+----+----+----+----+
// | VN | CD | DSTPORT | DSTIP |
// +----+----+----+----+----+----+----+----+
// 1 1 2 4
var response = new byte[8];
await nStream.ReadAsync(response.AsMemory(0, response.Length), cancellationToken).ConfigureAwait(false);
var reply = response[1];
if (reply != CommandReplyRequestGranted)
{
HandleCommandError(reply);
}
}