/// <summary>The private implementation of <see cref="ReadByte"/>. This implementation is specific to the Telnet protocol.</summary>
/// <returns>A <see cref="byte"/> of data destined for the application layer</returns>
/// <remarks>Telnet option negotiation happens inside this method, hidden from the client</remarks>
private byte GetApplicationInputByte()
{
// Keep reading bytes until we get one destined for the application layer
while (true)
{
if (InputIsAvailable)
{
byte inputByte = ReadByteFromTCP();
if (inputByte == TelnetCommand.IAC) // Decide whether to send the input to the Application, or process it within the NVT
{
byte possibleCommandDescriptionByte = ReadByteFromTCP();
if (possibleCommandDescriptionByte != TelnetCommand.IAC) // The IAC meant that a Telnet command follows, and the inputByte we just read is a command type.
{
TelnetCommand cmd = TelnetCommand.OfType(possibleCommandDescriptionByte).IncomingOn(this);
cmd.Process();
}
else // The IAC is part of a two-byte escape sequence, meaning a literal 0xFF character is part of the Application data stream
{
OnByteReceived(TelnetCommand.IAC);
return(TelnetCommand.IAC);
}
}
else // inputByte was NOT an IAC, so send it to the Application
{
OnByteReceived(inputByte);
return(inputByte);
}
}
else // Now that there's no more input to be read, we can send queued telnet commands
{
SendQueuedTelnetCommands();
}
}
void SendQueuedTelnetCommands()
{
while (CommandsToBeSent.Count > 0)
{
byte[] output = CommandsToBeSent.SelectMany(command => command.TelnetForm).ToArray();
WriteByteArray(output);
CommandsToBeSent.Clear();
}
}
}
/// <summary>Put the <see cref="TelnetCommand"/> <paramref name="commandToBeSent"/> in a queue so it can be sent when we finish reading input</summary> internal void EnqueueForSending(TelnetCommand commandToBeSent) => CommandsToBeSent.Add(commandToBeSent);
