def _iac_sniffer(self, byte):
        """Check incoming data for Telnet IAC sequences.

        Passes the data, if any, with the IAC commands stripped
        to _recv_byte().

        :param str byte: The byte to check
        :returns None:

        """
        # Are we not currently in an IAC sequence coming from the client?
        if self.telnet_got_iac is False:
            if byte == IAC:
                # Well, we are now
                self.telnet_got_iac = True
                return
            # Are we currently in a sub-negotiation?
            elif self.telnet_got_sb is True:
                # Sanity check on length.
                if len(self.telnet_sb_buffer) < 64:
                    self.telnet_sb_buffer += byte
                else:
                    self.telnet_got_sb = False
                    self.telnet_sb_buffer = ""
                return
            else:
                # Just a normal NVT character
                self._recv_byte(byte)
                return
        # Byte handling when already in an IAC sequence sent from the client
        else:
            # Did we get sent a second IAC?
            if byte == IAC and self.telnet_got_sb is True:
                # Must be an escaped 255 (IAC + IAC)
                self.telnet_sb_buffer += byte
                self.telnet_got_iac = False
                return
            # Do we already have an IAC + CMD?
            elif self.telnet_got_cmd:
                # Yes, so handle the option
                self._three_byte_cmd(byte)
                return
            # We have IAC but no CMD
            else:
                # Is this the middle byte of a three-byte command?
                if byte == DO:
                    self.telnet_got_cmd = DO
                    return
                elif byte == DONT:
                    self.telnet_got_cmd = DONT
                    return
                elif byte == WILL:
                    self.telnet_got_cmd = WILL
                    return
                elif byte == WONT:
                    self.telnet_got_cmd = WONT
                    return
                else:
                    # Nope, must be a two-byte command
                    self._two_byte_cmd(byte)