Null-Modem
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ZTerm.img_.sit (296.17 KB)
MD5: ec8ac9f8b4fe8bd503e708a03c2477a3
Stuffit_36_img.sit (623.98 KB)
MD5: e37af4f686b6cd59f4324476d08952e1
HyperTerm.7z (183.94 KB)
MD5: c521073b8fbb492f3024469540733ba4
Guides on emulating older applications
This is not an app.
Back in the days of BBS the Mac serial ports were the way to get connected to the world.
Most vintage Macs, except for the MacPlus, have two Mini DIN F8 connectors on their back.
These serial ports are of RS-422 type (see pict 4).
Good to know the RS-422 is downward compatible to RS-232 which was common with PCs until about 2010. Many office PCs still have this RS-232 port, if not one can be added via a PCI(E) card or by using a USB adapter.
Lets assume you got your vintage Mac and can beg, steal or borrow an old PC running Windows XP or Windows 2000. These two systems are the easiest counterpart talking to a Mac via serial, as they still come with the app HyperTerminal. Newer Windows rigs may be used too, using an app like Putty.
The biggest obstacle getting connected is the null-modem cable.
The name null-modem refers to the connection via land line modems, only that this cable does nothing accept crossing some wires internally.
It is fairly easy soldering such a cable yourself though. Best find a Mac serial cable with two Mini DIN 8-M connectors. Make sure that all pins are really wired, e.g. with a multi-meter, before cutting off one connector.
For the PC side you want a DE-9 F solder connector similar to the one in pict 1 and 2.
Connect the wires of the Mac serial cable to the D-sub 9 female connecter according to pict 3.
Now you need to add ZTerm to your Mac. (First DL) as ZTerm is aware of the needed file transfer protocols x-modem, y-modem and z-modem.
The files from the first DL can travel on a Mac floppy.
If you have no other way to write Mac floppies, Basilisk II Build 142 for Windows does write 1.4MB Mac floppies fine.
(App and instruction are to be found at Emaculation.com)
When everything went well, ZTerm on the Mac talks to HyperTerminal in Windows.
Files can be sent to and fro, but remember that resource forks of Mac apps will be destroyed on "foreign" file systems. Therefore applications need to be protected in a .sit or .hqx shell.
See second DL for StuffIt 3.6 to create .sit or hqx.
Because of the mediocre RS-232 port on PCs the serial connection is way slower than the 12Mbit/s the Mac´s RS-422 interface can handle.
Expect 5,7Mbit/s as a maximum, a 704K file as shown in picture 5 will take two minutes to travel over serial.
Anyway, even as this a slow boat, you can move big files from your vintage Mac to a new home - with enough patience. 
Edit:
Added HyperTerm as 3rd DL for Windows users.
The files are taken from a Windows XP installation. The app is still running with Windows 10 (64) basically. Some eye candy is missing though.
Comments
any sort of app for Snow Leopard could probably get a RS-232 to USB right at least hats what i have heard
Null-modem via serial port with a PB165 should work.
As written above, a Z-Modem compatible app is needed on sender and receiver side.
Would this work on a PowerBook 165
Sure, such an adapter is nice to have. Gave up soldering over time too.
Maybe the adapter would work with one of these? https://www.pccables.com/products/MINI-DIN8-M-to-DB9F-6FT-CABLE.html
. . . and then there's those of us who 'cheated' and just bought an inline null modem adapter from the 'Shack:
https://www.radioshack.com/products/gigaware-null-modem-adapter
God, that brings back memories. I remember getting my first 'high speed' modem (I think it was a Zoom 19.2kbps model), and it didn't work because I forgot to get a cable that supported hardware flow control:
http://www.brainboxes.com/faq/items/what-is-rts--cts-hardware-flow-control-
Thanks for the memory trip, 24bit!