Ruby's TCPSocket.open method will happily accept a string as the port parameter: socket = TCPSocket.open("waldorf", "7500") socket.close This code generates an exception in JRuby: socket = TCPSocket.open("waldorf", "7500") TypeError: can't convert String into Integer from (irb):4:in `open' from (irb):4:in `binding' from /Users/fletcher/Desktop/jruby-1.0/lib/ruby/1.8/irb.rb:150:in `eval_input' from /Users/fletcher/Desktop/jruby-1.0/lib/ruby/1.8/irb.rb:70:in `signal_status' from /Users/fletcher/Desktop/jruby-1.0/lib/ruby/1.8/irb.rb:189:in `eval_input' from /Users/fletcher/Desktop/jruby-1.0/lib/ruby/1.8/irb.rb:70:in `each_top_level_statement' from /Users/fletcher/Desktop/jruby-1.0/lib/ruby/1.8/irb.rb:190:in `loop' from /Users/fletcher/Desktop/jruby-1.0/lib/ruby/1.8/irb.rb:190:in `catch' from /Users/fletcher/Desktop/jruby-1.0/lib/ruby/1.8/irb.rb:190:in `eval_input' from /Users/fletcher/Desktop/jruby-1.0/lib/ruby/1.8/irb.rb:70:in `start' from :-1:in `catch' from /Users/fletcher/Desktop/jruby-1.0/lib/ruby/1.8/irb.rb:71:in `start' from :-1