on_fork advise

gistfile1.txt

irb(main):003:0> require 'socket'
=> true
irb(main):004:0> s = TCPServer.new 9999
=> #<TCPServer:fd 10>
irb(main):005:0> Thread.new { s.accept }
=> #<Thread:0x007fedf33f0e88 run>
irb(main):006:0> c = TCPSocket.new "0.0.0.0", 9999
=> #<TCPSocket:fd 11>
irb(main):007:0> Process.fork { p $$ }
on_fork: Detected open IO at fork: #<TCPServer:0x007fedf33e8f08>
on_fork: Detected open socket to 127.0.0.1:62284 at fork
on_fork: Detected open socket to 127.0.0.1:9999 at fork
=> 38218
irb(main):008:0> 38218

irb(main):009:0* exit