Question

I am reading data from a Telnet server with TcpClient as a byte array and convert into string with ASCII encoder, i.e.:

int size;
byte[] buf;
tcpclient.Read(buf,0,MAX_BUFFER_SIZE);
string resp = new System.Text.ASCIIEncoding().GetString(fullBuffer, 0, fullBuffer.Length);

and have buf with the read bytes. I want to extract (and answer later) IAC commands inside buf, not to have them in resp. Do you have an efficient suggested way.

What first comes to my mind is: Find “\0xFF” strings in resp (a) if followed by “\0xFF”, replace “\0xFF\0xFF” with “\0xFF” (b) if not extract followed byte as IAC and answer. resp.Remove() two characters.

Is that an efficient solution? Do you suggest to solve it in byte[] level (is there a way to have some values in byte[] that are ignored by ASCII encoder?) or after encoding into string?

Answer 1

What first comes to my mind is: Find “\0xFF” strings in resp (a) if followed by “\0xFF”, replace “\0xFF\0xFF” with “\0xFF” (b) if not extract followed byte as IAC and answer. resp.Remove() two characters.

Part a will work, but part b is lacking. There are several commands that consist of more than 2 bytes. You’re going to have to do more work and determine how many bytes each command should consume. For instance, the SB command will contain a variable number of bytes depending on what the suboption is.