Flynn

A Telnet client for classic Macintosh (68000/Mac Plus), targeting System 6.0.8 with MacTCP 2.1. Cross-compiled on Linux using Retro68.

This project was 100% vibe coded using Claude Code.

Features · Keyboard Shortcuts · Building · Testing · Acknowledgments · License

Telnet Session — neofetch over telnet with VT220 emulation	tmux Split Panes — box-drawing characters rendered via QuickDraw
Connect Dialog — saved host, port, and username auto-login	Claude Code via Flynn — the AI that built Flynn, running inside it

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Features

• VT100/VT220/xterm terminal emulation — runs vi, nano, tmux, mc, and other full-screen TUI apps over telnet
• Box-drawing characters — DEC Special Graphics rendered natively via QuickDraw for clean tmux panes, mc panels, and dialog borders
• UTF-8 support — accented characters, curly quotes, and symbols decoded and mapped to Mac Roman
• Resizable window — drag the grow box from 80x24 up to 132x50 cells, with NAWS negotiation
• 6 fonts — Monaco 9/12, Courier 10, Chicago 12, Geneva 9/10, including proportional font rendering
• Session bookmarks — save up to 8 hosts with one-click connect from the Session menu
• Username auto-login — sends your username at the login prompt automatically
• Mouse text selection — click-drag, double-click to select words, shift-click to extend, Cmd+C/V for copy/paste
• Scrollback — 96 lines of history, navigate with Cmd+Up/Down
• Control menu — send Ctrl-C, Ctrl-D, Ctrl-Z, Escape, Ctrl-L, and Break without a physical Ctrl key
• Keystroke buffering — batches fast typing into single TCP sends, no character loss
• M0110 keyboard support — Option key as Ctrl, Cmd+. as Escape, Cmd+1-0 for F-keys, designed for the original Mac Plus keyboard
• Dark mode — inverted display option for late-night telnet sessions
• Settings persistence — host, port, bookmarks, font, and preferences saved across launches
• 4MB Mac Plus — ~98KB on disk, ~60KB RAM footprint (~1.5% of 4MB). Runs on a Macintosh Plus with System 6.0.8 and MacTCP 2.1

Keyboard Shortcuts

Flynn is designed for the Apple M0110/M0110A keyboard, which lacks Escape and Control keys. These mappings also work on modern USB/ADB keyboards.

Action	Keys	Notes
Escape	Cmd+.	Classic Mac "Cancel" convention
Escape	Clear (keypad)	M0110A numeric keypad key
Escape	Esc key	Modern keyboards only (not on M0110)
Ctrl+key	Option+key	e.g., Option+C = Ctrl+C
Scroll up/down	Cmd+Up/Down	One line at a time
Scroll page	Cmd+Shift+Up/Down	One page at a time
Select text	Click+drag	Stream selection with inverse video
Select word	Double-click	Selects contiguous non-space word
Extend selection	Shift+click	Extends selection to click point
Copy	Cmd+C	Copies selection, or full screen if none
Paste	Cmd+V	Sends clipboard to connection
F1-F10	Cmd+1..0	For M0110 keyboards without function keys
Bookmarks	Cmd+B	Open bookmark manager
Connect	Cmd+N	Open connect dialog

Building

Requires the Retro68 cross-compilation toolchain. Build it from source (68k only):

git clone https://github.com/autc04/Retro68.git
cd Retro68 && git submodule update --init && cd ..
mkdir Retro68-build && cd Retro68-build
bash ../Retro68/build-toolchain.bash --no-ppc --no-carbon --prefix=$(pwd)/toolchain

Then build Flynn:

./build.sh

Testing

Uses Snow emulator (v1.3.1) with a Mac Plus ROM and System 6.0.8 SCSI hard drive image. Snow supports DaynaPORT SCSI/Link Ethernet emulation for MacTCP networking. The emulator can be fully automated via X11 for unattended testing. See docs/TESTING.md for details.

Acknowledgments

• Claude Code — AI-assisted development by Anthropic. Flynn was built entirely through agentic AI pair programming.
• Retro68 by Wolfgang Thaller — the 68k Macintosh cross-compilation toolchain that makes building classic Mac applications on modern Linux possible.
• Snow — a Rust-based classic Macintosh emulator with low-level hardware emulation, DaynaPORT SCSI/Link networking, and BlueSCSI Toolbox support. Used for all development testing.
• wallops by joshua stein — IRC client for classic Macintosh. MacTCP wrapper (tcp.c/tcp.h), DNS resolution (dnr.c/dnr.h), utility functions (util.c/util.h), and MacTCP.h are used directly from this project. ISC license.
• subtext by joshua stein — BBS server for classic Macintosh. The Telnet IAC protocol implementation (telnet.c/telnet.h) served as the reference for Flynn's client-side telnet engine. ISC license.

License

ISC License. See LICENSE for full details.