matthewmrichter/mooftcp: Drop-in MacTCP replacement for System 6 / 68000 Macs · GitHub

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.

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.

• 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.

Installer	MoofTCP Lite panel

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.

• 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.

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).

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

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.

• 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.

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.

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.

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

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.

• 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.

• 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.

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.