On Thu, Jun 24, 2021 at 1:41 PM Grant Taylor via cctalk <cctalk at classiccmp.org> wrote: https://en.wikipedia.org/wiki/TD/SMP TD/SMP, short for Terminal Device/Session Management Protocol, was a terminal multiplexer system introduced by DEC on their VT330/340 terminals in 1987. The terminal-side was referred to as SSU. TD/SMP allowed data from two separate host sessions to be sent to a compatible computer terminal over a single serial port. The format was patented and never described in depth, limiting it to DEC's own terminal servers and terminals. Also supported by the VT420, VT510, VT520, VT525 Terminal device session management protocol https://patents.google.com/patent/US4791566 https://patents.google.com/patent/US5165020 SSU software was available on OpenVMS

The patent goes into considerable depth on the "preferred embodiment" with descriptions of the protocol with flow control etc. and it looks like it could be pretty easy to reverse engineer if the actual implementation is similar to the description in the patent. If one had a working example to play with of course. Could be a fun little project. The flow control is kinda interesting. The receiver sends "transmit credits" to the sender who will consume them in the process of sending data and then stop until more credits are received. On Thu, Jun 24, 2021 at 4:25 PM Glen Slick via cctalk <cctalk at classiccmp.org> wrote: