socket_connect_fix

On macOS (and possibly other BSD-derived systems), Crystal's Socket#connect can report a refused connection as successful. The refusal is only visible in the kernel's SO_ERROR, which Crystal does not read. Consequences:

• TCPSocket.new("localhost", port) stops at ::1 and never tries 127.0.0.1, so servers listening only on IPv4 (e.g. Ollama) appear unreachable.
• Any refused connection returns a dead socket that fails later with a misleading error such as getpeername: Invalid argument.

This shard checks SO_ERROR after connect and reports failures as Socket::ConnectError, so Crystal's existing address fallback works.

Installation

dependencies:
  socket_connect_fix:
    github: nogginly/socket_connect_fix.cr

Usage

require "socket_connect_fix"

Require it once, anywhere in the application. The change applies to every socket in the program, including those opened by HTTP::Client and database drivers. Libraries should not require it; applications opt in.

Compatibility

CI runs the specs with Crystal 1.20 and the latest release on Linux and macOS, and 1.20 on Windows. The fix applies on Unix only; it is a no-op on Windows. It redefines Socket#connect(addr, timeout, &) and relies on that signature. Re-run the specs when upgrading Crystal, and remove the shard once the upstream fix ships.

Development

crystal spec
crystal spec -Devloop=libevent
crystal spec -Dsocket_connect_fix_disabled   # on macOS, closed-port specs should fail

Contributions, by invitation!

With apologies, at this time contributions to this project are by invitation only and limited to people I know and see often.

• These are early days for the project and I am busy with family and work.
• At this time I want to work on this at a manageable pace.