Issue #21104 has been updated by chokkoy (Naoyuki Yamada). After I upgraded MacOS from 15.3 to 15.4, the issue seems to be resolved! ``` ➜ ruby-sandbox sw_vers ProductName: macOS ProductVersion: 15.4.1 BuildVersion: 24E263 ➜ ruby-sandbox echo $RUBY_TCP_NO_FAST_FALLBACK. # the environment variable is not set. ➜ ruby-sandbox ruby -v ruby 3.4.2 (2025-02-15 revision d2930f8e7a) +PRISM [arm64-darwin24] ➜ ruby-sandbox irb irb(main):001> require "socket" irb(main):002> s = Socket.tcp("example.com", 80) irb(main):003> s.write "GET / HTTP/1.1\r\nHost: example.com\r\nConnection: close\r\n\r\n" irb(main):004> puts s.gets(nil) irb(main):005> s.close HTTP/1.1 200 OK Content-Type: text/html ETag: "84238dfc8092e5d9c0dac8ef93371a07:1736799080.121134" Last-Modified: Mon, 13 Jan 2025 20:11:20 GMT Cache-Control: max-age=3318 Date: Mon, 05 May 2025 08:20:15 GMT Content-Length: 1256 Connection: close X-N: S <!doctype html> <html> <head> <output truncated> ``` ---------------------------------------- Bug #21104: Net::HTTP connections failing in Ruby >= 3.4.0 on macOS with Happy Eyeballs enabled https://bugs.ruby-lang.org/issues/21104#change-112891 * Author: mjt58 (Mike Thompson) * Status: Open * ruby -v: ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [arm64-darwin24] * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- A project I work on recently upgraded Ruby to 3.4.1 from 3.3.5. Following the upgrade, and when running locally on my Mac, all attempts to connect to an external service within the project over http(s) fail. We use `mise` for managing development tool dependencies, including Ruby, and I am using macOS 15.3. For example running something as simple as: ``` require 'net/http' puts Net::HTTP.get(URI('https://bbc.co.uk')) ``` Will fail with the following stack trace: ``` /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/protocol.rb:46:in 'OpenSSL::SSL::SSLSocket#connect_nonblock': Connection reset by peer - SSL_connect (Errno::ECONNRESET) from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/protocol.rb:46:in 'Net::Protocol#ssl_socket_connect' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:1736:in 'Net::HTTP#connect' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:1636:in 'Net::HTTP#do_start' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:1625:in 'Net::HTTP#start' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:1064:in 'Net::HTTP.start' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:824:in 'Net::HTTP.get_response' from /path/to/.local/share/mise/installs/ruby/3.4.1/lib/ruby/3.4.0/net/http.rb:805:in 'Net::HTTP.get' from request.rb:2:in '<main>' ``` I tried different versions of Ruby and confirmed that the issue appears with 3.4.0. After reading the release notes for this version, I tried setting `RUBY_TCP_NO_FAST_FALLBACK=1` and this worked, allowing me to work around the problem. This issue has also been encountered by others, please see: https://github.com/rubygems/rubygems/issues/8390 -- https://bugs.ruby-lang.org/