start

# File lib/webrick/server.rb, line 151
    def start(&block)
      raise ServerError, "already started." if @status != :Stop
      server_type = @config[:ServerType] || SimpleServer

      setup_shutdown_pipe

      server_type.start{
        @logger.info            "#{self.class}#start: pid=#{$$} port=#{@config[:Port]}"
        @status = :Running
        call_callback(:StartCallback)

        shutdown_pipe = @shutdown_pipe

        thgroup = ThreadGroup.new
        begin
          while @status == :Running
            begin
              sp = shutdown_pipe[0]
              if svrs = IO.select([sp, *@listeners])
                if svrs[0].include? sp
                  # swallow shutdown pipe
                  buf = String.new
                  nil while String ===
                            sp.read_nonblock([sp.nread, 8].max, buf, exception: false)
                  break
                end
                svrs[0].each{|svr|
                  @tokens.pop          # blocks while no token is there.
                  if sock = accept_client(svr)
                    unless config[:DoNotReverseLookup].nil?
                      sock.do_not_reverse_lookup = !!config[:DoNotReverseLookup]
                    end
                    th = start_thread(sock, &block)
                    th[:WEBrickThread] = true
                    thgroup.add(th)
                  else
                    @tokens.push(nil)
                  end
                }
              end
            rescue Errno::EBADF, Errno::ENOTSOCK, IOError => ex
              # if the listening socket was closed in GenericServer#shutdown,
              # IO::select raise it.
            rescue StandardError => ex
              msg = "#{ex.class}: #{ex.message}\n\t#{ex.backtrace[0]}"
              @logger.error msg
            rescue Exception => ex
              @logger.fatal ex
              raise
            end
          end
        ensure
          cleanup_shutdown_pipe(shutdown_pipe)
          cleanup_listener
          @status = :Shutdown
          @logger.info "going to shutdown ..."
          thgroup.list.each{|th| th.join if th[:WEBrickThread] }
          call_callback(:StopCallback)
          @logger.info "#{self.class}#start done."
          @status = :Stop
        end
      }
    end