&& this.sbuf[ 7 ] == (byte) 'B' ) {
                this.smb2 = true;
                // also read the rest of the header
                int lenDiff = Smb2Constants.SMB2_HEADER_LENGTH - SmbConstants.SMB1_HEADER_LENGTH;
                if ( readn(this.in, this.sbuf, 4 + SmbConstants.SMB1_HEADER_LENGTH, lenDiff) < lenDiff ) {
                    return null;
                }