JRuby 1.0.1 fails to bind to socket when using DRb. The response is always "Address in use (Errno::EADDRINUSE)" even though the port is free. This behaviour was duplicated on both Ubuntu Linux 7.04 and Mac OS X 10.4.10, both with the binary JRuby 1.0.1 tarball. Trace of a call: /Developer/Java/jruby-1.0.1/lib/ruby/1.8/drb/drb.rb:865:in `open': Address in use (Errno::EADDRINUSE) from /Developer/Java/jruby-1.0.1/lib/ruby/1.8/drb/drb.rb:865:in `open_server' from /Developer/Java/jruby-1.0.1/lib/ruby/1.8/drb/drb.rb:759:in `open_server' from /Developer/Java/jruby-1.0.1/lib/ruby/1.8/drb/drb.rb:1339:in `each' from /Developer/Java/jruby-1.0.1/lib/ruby/1.8/drb/drb.rb:757:in `open_server' from /Developer/Java/jruby-1.0.1/lib/ruby/1.8/drb/drb.rb:1339:in `initialize' from /Developer/Java/jruby-1.0.1/lib/ruby/1.8/drb/drb.rb:1627:in `new' from /Developer/Java/jruby-1.0.1/lib/ruby/1.8/drb/drb.rb:1627:in `start_service' from jruby_server.rb:49 Where the last line looks like: DRb.start_service 'druby://127.0.0.1:4999', StateServer.new (i.e. no matter which port is chosen the result is always the same). The exact same code works fine with JRuby 1.0.0