Re: Re: Question for telnet/BBS gurus.
  By: Deon George to Rob Swindell on Tue Jun 23 2020 01:13 pm

 >   Re: Re: Question for telnet/BBS gurus.
 >   By: Rob Swindell to Deon George on Mon Jun 22 2020 07:32 pm
 >
 >  RS> Telnet binary mode has to do with the translation of received CR/LF and
 >  RS> CR/NUL pairs to a single carriage-return character (0x0D) and nothing
 >  RS> to do with the Telnet IAC character (0xFF) which must always be escaped
 >  RS> and parsed correctly, always, binary mode or not.
 >
 > But isnt in telnet binary mode, 0xFF needs to be received twice consectively
 > before the other end should interpret what should follow?

No. Only an actual 0xFF data byte needs to be escaped (by sending an IAC). This
is true whether in binary mode or not.

 > I must admit I havent read the finer details of how things are parsed when
 > in it goes in this mode - but I assumed this mode assisted binary file
 > transfers that are likely to have those special control chars that would
 > normally be intepreted as IAC commands.

No, Telnet binary mode only affects the interpretation of the CR/LF and CR/NUL
byte pairs, which most definitely are likely to be contained in many/most file
transfers and thus need to have binary mode enabled to be received correctly
(e.g. for chksum/crc validation purposes, if nothing else).

                                            digital man

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