This class provides input and output streams for telnet clients. This class overrides write to do CRLF processing as specified in RFC 854. The class assumes it is running on a system where lines are terminated with a single newline <LF> character. This is the relevant section of RFC 824 regarding CRLF processing:

The sequence "CR LF", as defined, will cause the NVT to be
positioned at the left margin of the next print line (as would,
for example, the sequence "LF CR").  However, many systems and
terminals do not treat CR and LF independently, and will have to
go to some effort to simulate their effect.  (For example, some
terminals do not have a CR independent of the LF, but on such
terminals it may be possible to simulate a CR by backspacing.)
Therefore, the sequence "CR LF" must be treated as a single "new
line" character and used whenever their combined action is
intended; the sequence "CR NUL" must be used where a carriage
return alone is actually desired; and the CR character must be
avoided in other contexts.  This rule gives assurance to systems
which must decide whether to perform a "new line" function or a
multiple-backspace that the TELNET stream contains a character
following a CR that will allow a rational decision.

   Note that "CR LF" or "CR NUL" is required in both directions
   (in the default ASCII mode), to preserve the symmetry of the
   NVT model.  Even though it may be known in some situations
   (e.g., with remote echo and suppress go ahead options in
   effect) that characters are not being sent to an actual
   printer, nonetheless, for the sake of consistency, the protocol
   requires that a NUL be inserted following a CR not followed by
   a LF in the data stream.  The converse of this is that a NUL
   received in the data stream after a CR (in the absence of
   options negotiations which explicitly specify otherwise) should
   be stripped out prior to applying the NVT to local character
   set mapping.