CSend - Cross-Platform P2P Chat

Peer-to-peer text chat between Classic Macs and modern systems over a LAN. Built on the PeerTalk SDK for all networking.

Builds

Target	Platform	Network	Output
csend-posix	Linux / macOS	POSIX sockets	build/csend-posix
csend-mac (68k)	System 7+	MacTCP	build-68k/csend-mac.bin
csend-mac (68k)	System 7.5+	Open Transport	build-68k-ot/csend-mac.bin
csend-mac (PPC)	System 7+	MacTCP	build-ppc-mactcp/csend-mac.bin
csend-mac (PPC)	System 7.5+	Open Transport	build-ppc-ot/csend-mac.bin

Prerequisites

The full dependency chain for building csend:

• Retro68 — Classic Mac cross-compiler (fork with OT fixes). Only needed for Classic Mac targets.
• clog — Minimal C89 logging library. Built from source automatically via FetchContent.
• PeerTalk SDK — Networking SDK for discovery, connections, and messaging across POSIX/MacTCP/OpenTransport.

Dependency Chain

Retro68 -> clog -> peertalk -> csend

Environment Variables

Variable	Default	Description
$CLOG_DIR	~/clog	Path to the clog source directory
$PEERTALK_DIR	~/peertalk	Path to the PeerTalk SDK source directory
$RETRO68_TOOLCHAIN	~/Retro68-build/toolchain	Path to the Retro68 toolchain install

Setup

Run ./setup.sh to bootstrap everything from scratch. It will clone and build all dependencies (Retro68, clog, peertalk) and configure the environment so you can build all csend targets.

Building

Requires PeerTalk SDK, clog, and Retro68 (fork with OT fixes) for Classic Mac targets.

# POSIX
cmake -B build -DCLOG_DIR=$CLOG_DIR && cmake --build build

# 68k MacTCP
cmake -B build-68k \
  -DCMAKE_TOOLCHAIN_FILE=$RETRO68_TOOLCHAIN/m68k-apple-macos/cmake/retro68.toolchain.cmake \
  -DPT_PLATFORM=MACTCP -DCLOG_DIR=$CLOG_DIR
cmake --build build-68k

# PPC Open Transport
cmake -B build-ppc-ot \
  -DCMAKE_TOOLCHAIN_FILE=$RETRO68_TOOLCHAIN/powerpc-apple-macos/cmake/retroppc.toolchain.cmake \
  -DPT_PLATFORM=OT -DCLOG_DIR=$CLOG_DIR
cmake --build build-ppc-ot

Usage

POSIX

./build/csend-posix <username>

# Commands
/list                      # Show connected peers
/send <peer_num> <message> # Send to specific peer
/broadcast <message>       # Send to all peers
/debug                     # Toggle debug output
/test                      # Run automated test sequence
/quit                      # Exit

Classic Mac

Deploy .bin to real hardware using the classic-mac-hardware-mcp MCP server. The GUI provides a message area, input field, peer list, send button, broadcast checkbox, and debug toggle.

Architecture

csend is a thin UI layer on top of PeerTalk. The SDK handles discovery, connections, and messaging. csend provides the interface.

posix/              POSIX terminal UI (2-thread: main PT_Poll + stdin input)
classic_mac/        Classic Mac Toolbox UI (single-threaded event loop)
shared/             Common definitions, Classic Mac UI components
MPW_resources/      ResEdit binary resources (.finf/.rsrc metadata)

• POSIX: C11, pthreads for stdin only, SPSC ring buffer for command queue
• Classic Mac: C89, WaitNextEvent + PT_Poll in idle handler
• Shared: MSG_CHAT message type, BUFFER_SIZE constant

Demo

• Latest demo
• Original demo