# File lib/puma/binder.rb, line 250
    def add_unix_listener(path, umask=nil)
      @unix_paths << path

      # Let anyone connect by default
      umask ||= 0

      begin
        old_mask = File.umask(umask)

        if File.exists? path
          begin
            old = UNIXSocket.new path
          rescue SystemCallError
            File.unlink path
          else
            old.close
            raise "There is already a server bound to: #{path}"
          end
        end

        s = UNIXServer.new(path)
        @ios << s
      ensure
        File.umask old_mask
      end

      s
    end