An idea: TCP/IP to serial bridge (modem emulator)

#31 Sat, 9 Aug 2008 - 22:44

(a) in an old mac with ethernet

How convenient!

#32 Sun, 10 Aug 2008 - 05:47

And depending on the micro, the Ethernet MAC would be built in.

#33 Tue, 12 Aug 2008 - 20:24

You don't really have "TCP/IP to serial bridges".

Sorry to come to this thread so late. Surely we do have TCP/IP to serial bridges?

TCP/IP follows the ISO layer standards. Serial comms (RS-232 and RS-422) follow earlier monloithic standards. A bridge is therefore necessary for the two different standards to communicate. Typical application of a TCP/IP to serial bridge is to connect old display signs (programmable via serial) to a modern network.

Alas they don't help with this problem.

#34 Tue, 12 Aug 2008 - 20:56

At this point, I don't know how these bridges are wrapping data so I don't know if they will be useful.

For the record, and it may be of help to some of the Apple II folks. With a TCP/IP to serial bridge, you have a set of libraries on the TCP/IP connected host which capture commands to a virtual serial port (sent as if you were using a VT terminal etc) and encapsulate them in TCP. I've seen device specs that list Linux and Windows support, but not Mac OS X or earlier. The TCP packets whizz along the network to the bridge, which assembles them into the right order, and then translates them back into serial.

And it obviously works in the opposite way.

From this we can assume that the bridges have some cache in order to re-order out of sync TCP packets. Probably enough to cope with out of sync TCP packets emulating a 9600bps connection, but not 230kbps.