A long time ago, in a land far, far away… before ethernet was widely deployed, Macs were networked via AppleShare over AppleTalk, which itself made use of LocalTalk, a serial connection between two or more Macs, printers etc. LocalTalk was capable of the whopping great transfer rate of 230 Kbps. This may seem slow by today’s standards, but back in the mists of time, when the 1200 baud modem (a glacial 1.2 Kbps!) was the speed king of the day, 230 Kbps seemed blazingly fast!

When my efforts to LocalTalk between my Apple IIGS and a Mac failed miserably, I decided to drop back and make sure I could get LocalTalk to work between two Macs first, thus ensuring that I had a reasonable grasp of what it takes to make LocalTalk go. The simplest form of a LocalTalk network involves just two Macs, directly connected via a single LocalTalk cable plugged into the printer port of each.
Everything I have read said that this was the trivial case; the easiest form of a LocalTalk network that could be put together. Assuming that AppleShare and AppleTalk were already loaded on the Macs, all that was necessary was to connect the Macs together via a LocalTalk cable whose two ends were plugged into the printer port of each Mac. The last step was then to change the AppleTalk connection from “Ethernet” to “Printer Port” and it should just work…
And guess what? …it just did! In a radical departure from the usual narrative of these posts, there were no irrational problems to solve, no major issues to overcome, no new software to load… nothing. It all just worked! How very nice for a change!
The web-based research I did before attempting to connect the two test Macs made it clear that there are a universe of variations on this topic, including the very successful Farallon PhoneNet. In addition, the specific steps to be taken vary based on the version of Mac OS each machine is running, and the exact form of the physical connection being used. So, with all this variability in mind, here is EXACTLY what I did to get LocalTalk between two Macs working.
The two machines in question were a Mac IIfx running Mac OS 7.0.1 and a Quadra 840AV running Mac OS 8.1. Each OS version is preconfigured with AppleShare-based Personal File Sharing (a.k.a. AppleShare File Server) and these two Macs are known to network with each other successfully when using AppleTalk over Ethernet (EtherTalk vs. LocalTalk).
I concluded from this that the AppleShare/AppleTalk software was already in place and set up properly. All I had to do was physically connect the two machines, printer port to printer port, swap the AppleTalk connection from “Ethernet” (EtherTalk) to “Printer Port” (LocalTalk) and enable File Sharing. With all of this done, each Mac should “see” the other in Chooser, and each Mac should be able to mount volumes from the other and transfer files.
Let’s decompose this and look at each step. First the physical connection. I got on Amazon and ordered “C2G 02318 8-Pin Mini-DIN M/M Serial RS232 Cable, Beige (10 Feet, 3.05 Meters)”.

Pretty much from the Mac II onwards, the DIN8 connector was used for printer ports, and so this was definitely the correct cable to get, at least from a plug compatibility perspective. With both machines powered down, I ran one end of this cable to each of the printer ports of the two Macs and plugged them in. So far, so good.
The process for swapping the AppleTalk connection to the printer port was different on each of the two Macs due to their Mac OS version differences.
On the Mac IIfx (Mac OS 7.0.1), there is no AppleTalk control panel. Instead, you go to the Network control panel and there select LocalTalk vs. EtherTalk. This accomplishes the switch of AppleTalk from the ethernet port to the printer port.

On the Quadra 840AV (Mac OS 8.1), there IS an AppleTalk control panel. There you select “Printer Port” vs. “Ethernet”, which again shifts AppleTalk over to the printer port of the machine.

Like the AppleTalk port switching, enabling File Sharing was also different between the two machines, again due to their different Mac OS versions.
On the Mac IIfx (Mac OS 7.0.1) I went to the Sharing Setup control panel and turned on File Sharing.

Then I went back to the desktop and selected the boot drive. From the menu bar File menu, I selected “Sharing…” and ticked the “Share this item and its contents” box. This step gave File Sharing something to share!

On the Quadra 840AV (Mac OS 8.1) I went to the File Sharing control panel and again turned on File Sharing.
[include screenshot of Quadra 840AV File Sharing control panel].
Then I went back to the desktop, but instead of sharing the entire boot volume, I decided to try something a little more granular, and instead created a new folder called Shared840AV and then shared it using the menu bar File Menu “Sharing…” selection. Again, File Sharing had something to share.

That was it! I was ready to test it all out. On the Mac IIfx, I started Chooser. Once it was up, I was careful to check that the radio buttons at the bottom right were set for “AppleTalk Active”. Then I selected the AppleShare icon from the icon set on the left of the Chooser dialog and boom! …up popped the Quadra 840AV in the Chooser pane where available AppleTalk servers should be presented!

I selected the Quadra 840AV’s boot volume from the presented set of volumes and it mounted successfully on the Mac IIfx desktop. I was able to copy files from the newly mounted Quadra 840AV to the Mac IIfx desktop and visa versa. At this point I will note… yup, it is SLOW! A 230 Kbps link is not much of a speed demon! It took an observable amount of time to transfer 400 KB files back and forth. It was tolerable, but slow by today’s standards.
Now I repeated this whole exercise from the other side. From the Quadra 840AV’s Chooser, I selected the Mac IIfx and then selected its boot volume from the presented list of volumes. Again, I was careful to ensure that AppleTalk was set to Active via the radio buttons in the lower right of the Chooser dialog. Again I was able to successfully “see” the other Mac and copy files back and forth, and again, it was not much of a speed demon while doing it.

So there you have it! Networking two Macs via AppleShare/AppleTalk over LocalTalk… every bit as easy as the material you will read online makes it sound.
One note of caution. Also from Amazon, and from the same manufacturer as the LocalTalk cable used in all of the above testing, I order an extension cable as well, since the two Macs are of such a distance apart that the one cable just barely makes it.

This did not work! When I took the working LocalTalk cable and simply added the extension cable to the end of it prior to use, neither Mac would see the other in Chooser. I am not sure what the issue is but be forewarned. It could be a maximum length limitation, it could be poor-quality cable, it could be both, or it could be something entirely different, but no matter what, using at least that extender cable does not seem to be a good idea, even if using an extender cable in general is a good idea!
And one last caveat. Connecting two Macs directly really IS the trivial case. If you want to create a REAL network, with multiple Macs, and perhaps a printer or two, you will need some LocalTalk Connector kits, one per Mac or Printer on the network. Happily, these are still in ready supply on eBay. The one shown below is one of many presently on offer, but with the distinction of being NOS (New Old Stock) – still in the original shrink wrap.

With that, I will wrap this post up and wish you happy (LocalTalk) networking!