On 2019 Aug 01 16:40:54, you wrote to me:

 TR> Thanks for the technical correction.

you're welcome...

 TR> The question is the same though, why use port 3456 instead of 3141

maybe more than one machine behind that IP?

 TR> since using port 3141 allows the Sysop to add VDM flag to the nodelist
 TR> without adding the port number.

the nodelist flag for vmodem is IVM ;)  those old ones that were not
prefixed by "I" are obsolete and no longer used in the
distributed nodelist... some abandoned software still in use may still
require them, though... it should also be noted that ITN should not be used
unless there is a mailer on telnet...

http://ftsc.org/docs/fts-5001.006

        Default
   Flag     port Description
  ---------------------------

   IBN    24554  Binkp (FTS-1026 - FTS-1030)
   IFC    60179  RAW ifcico (FTS-1024)
   IFT       21  FTP (RFC-0959); Note there is currently no widely
                 accepted authentication scheme for FTP transfers by
                 Fidonet mailers.
   ITN       23  Telnet connection using FTS-1 or any other protocol
                 designed for classic POTS and modem.
   IVM     3141  Vmodem connection using FTS-1 or any other protocol
                 designed for classic POTS and modem.
   IP      none  Mostly used during the introduction of IP capable
                 systems to the nodelist. Denotes an unspecified
                 protocol. (Deprecated)


)\/(ark

Once men turned their thinking over to machines in the hope that this would
set them free. But that only permitted other men with machines to enslave
them.
... I wish I had a lower IQ so I could enjoy your company!
---