MoofTCP – A modern replacement for MacTCP on 68k Macs

A modern, memory-lean replacement for MacTCP on 68k Macs running System 6.

MoofTCP is a drop-in replacement for Apple's MacTCP. Programs written for MacTCP run on it unchanged, but underneath it is a fresh TCP/IP stack written from scratch in portable C, with its own control panel, installer and DHCP client. It was built for a Mac Classic with 4 MB of RAM, so every byte counts.

Why?

MacTCP is wonderful, but it is old, and on a 4 MB Mac Classic with a SCSI Wi-Fi/Ethernet adapter like BlueSCSI it can be slow to answer, hungry for memory, and awkward to set up. MoofTCP aims, in this order, for:

1. Reliability. No hangs, no leaks, no surprises when apps quit.
2. Low latency for interactive use, like typing in a telnet session.
3. Throughput, for handling quasi-modern use cases.

...all while using no more resident memory than MacTCP does.

Features

• Drop-in compatible. Implements the MacTCP .IPP driver interface (TCP, UDP, ICMP echo) and the dnrp name resolver. Your existing MacTCP programs just work.
• DHCP or a fixed address. Pick either in the control panel. Don't need to manage static IP anymore.
• MoofTCP Lite. A build without DHCP that saves about 5 KB of system memory, for tight machines. One installer holds both; a checkbox picks which one.
• A friendly installer. It moves MacTCP's files aside, installs MoofTCP, and its Remove button puts everything back exactly as it was. An interrupted install repairs itself.
• MultiFinder-aware. Quitting an app that had connections open cleans up after it.
• Built-in diagnostics. An optional in-memory log and a small MoofDiag tool for bug reports.
• A portable core. The TCP/IP stack in core/ has no malloc and no global state, and is tested on the desktop with sanitizers and fuzzers.

Screenshots

Installer	MoofTCP Lite panel

Quick start

1. Download MoofTCP-1.0.dsk, MoofTCP-1.0.hqx or MoofTCP-1.0.sit from the Releases page and get it onto your Mac (a BlueSCSI shared folder works well).
2. Open MoofTCP Installer, leave Lite version (no DHCP) unticked, and click Install.
3. Restart the Mac.
4. Open Control Panels, MoofTCP, enter your IP address, mask, router and DNS server (or tick Get the address by DHCP), and save.
5. Restart again. You're online.

To go back to MacTCP, run the installer and click Remove. The Read Me file in the release has the details, including how to switch between MoofTCP and MoofTCP Lite.

StuffIt Lite 3.6 is tested as working for expanding the .hqx packages.

What you need

• A 68k Mac with System 6.0.8 (the version it was tested on). Please report back if it works on other versions!
• An Ethernet adapter that provides the .ENET0 driver, such as a BlueSCSI v2 WiFi with DaynaPORT. MoofTCP does not include an Ethernet driver.

Compatibility

Tested on a real Mac Classic (System 6.0.8, 4 MB, BlueSCSI v2 WiFi with DaynaPORT) and in the Snow emulator.

Have a program that doesn't work? Please open an issue (see below).

Memory

MultiFinder grows the system heap on demand, so free memory varies more there.

Something went wrong?

MoofTCP keeps a small diagnostic log in memory. If a program misbehaves but the Mac keeps running, run MoofDiag right away (it is in the release's diagnostic tools download), and open an issue with the MoofDiag.out file it writes next to itself, plus a note about what you were doing. Feel free to ask your LLM to analyze the codebase and the diagnostic output as well and to submit fix PRs.

Known limitations

• No IPv6.
• Tested only with the DaynaPORT Ethernet driver on System 6.0.8.
• DHCP is basic: no lease RELEASE, no INIT-REBOOT and no address-conflict probe. While it runs, programs cannot use UDP port 68. With no DHCP server, the first open waits about 10 seconds and then fails.

Building from source

You only need Docker. The pinned Retro68 cross-compiler image is pulled automatically.

scripts/build-mac.sh MoofTCP              # the MoofTCP file -> build-mac/moof/
MT_LITE=1 scripts/build-mac.sh MoofTCP    # MoofTCP Lite -> build-mac-lite/
scripts/release.sh --force 1.0            # one installer with both -> dist/MoofTCP-1.0.{dsk,hqx,sit}

release.sh also needs hfsutils, macutils, unar, gcc and Python 3.

Running the tests

The portable core and the glue logic are tested on your desktop with gcc and CMake (AddressSanitizer and UBSan are on by default):

cmake -S . -B build && cmake --build build
ctest --test-dir build --output-on-failure
cmake -S . -B build-lite -DMT_NO_DHCP=ON   # the Lite configuration

The emulator tests (Snow) need Apple system software and the BlueSCSI DaynaPORT image. Those are not in this repository and you must supply them yourself; the scripts in scripts/ (setup-home.sh, golden-stage.sh) show what is expected.

Project layout

core/      portable TCP/IP stack (no malloc, no globals), host-tested
mac/       Mac glue: .IPP driver, INIT, resolver, control panel, installer, diagnostic apps
tests/     host tests (ctest), including fuzzers
scripts/   build, release, emulator and hardware-session scripts
tools/     pinned tool versions; tools/sit is a small StuffIt-format writer

Contributing

Bug reports, compatibility reports ("program X does/doesn't work") and pull requests are welcome. For code changes, please read CONTRIBUTING.md and run the host tests first (see above). CLAUDE.md is a detailed map of the code and its rules. Security problems: see SECURITY.md.

Credits

• Retro68 for the 68k cross-compiler.
• Snow for the Mac emulator the tests run in.
• BlueSCSI and DaynaPORT for the network hardware this was built around.
• Claude Code was used to develop this project, with human planning and testing.

TODO

• More comprehensive bake-in testing on real hardware as we use it
• Remake Daynaport similarly (stay tuned for MoofPort)
• Review the BlueSCSI codebase for opportunities to integrate more tightly for better performance
• There is potential for further algorithm optimization for added performance on smaller or older systems.

License

MIT. "MacTCP" and "StuffIt" are trademarks of their owners and are used here only to describe compatibility. MoofTCP contains no Apple or third-party code; building it uses Apple's interfaces as shipped in the Retro68 toolchain.