class DEBUGGER__::UI_TcpServer

# File debug-1.9.1/lib/debug/server.rb, line 386
def initialize host: nil, port: nil
  @local_addr = nil
  @host = host || CONFIG[:host]
  @port_save_file = nil
  @port = begin
    port_str = (port && port.to_s) || CONFIG[:port] || raise("Specify listening port by RUBY_DEBUG_PORT environment variable.")
    case port_str
    when /\A\d+\z/
      port_str.to_i
    when /\A(\d+):(.+)\z/
      @port_save_file = $2
      $1.to_i
    else
      raise "Specify digits for port number"
    end
  end
  @uuid = nil # for CDP

  super()
end

# File debug-1.9.1/lib/debug/server.rb, line 420
    def accept
      retry_cnt = 0
      super # for fork

      begin
        Socket.tcp_server_sockets @host, @port do |socks|
          @local_addr = socks.first.local_address # Change this part if `socks` are multiple.
          rdbg = File.expand_path('../../exe/rdbg', __dir__)
          DEBUGGER__.warn "Debugger can attach via TCP/IP (#{@local_addr.inspect_sockaddr})"

          if @port_save_file
            File.write(@port_save_file, "#{socks[0].local_address.ip_port.to_s}\n")
            DEBUGGER__.warn "Port is saved into #{@port_save_file}"
          end

          DEBUGGER__.info <<~EOS
          With rdbg, use the following command line:
          #
          #   #{rdbg} --attach #{@local_addr.ip_address} #{@local_addr.ip_port}
          #
          EOS

          case CONFIG[:open]
          when 'chrome'
            chrome_setup
          when 'vscode'
            vscode_setup @local_addr.inspect_sockaddr
          end

          Socket.accept_loop(socks) do |sock, client|
            @client_addr = client
            yield @sock_for_fork = sock
          end
        end
      rescue Errno::EADDRINUSE
        if retry_cnt < 10
          retry_cnt += 1
          sleep 0.1
          retry
        else
          raise
        end
      rescue Terminate
        # OK
      rescue => e
        $stderr.puts e.inspect, e.message
        pp e.backtrace
        exit
      end
    ensure
      @sock_for_fork = nil

      if @port_save_file && File.exist?(@port_save_file)
        File.unlink(@port_save_file)
      end
    end

# File debug-1.9.1/lib/debug/server.rb, line 407
    def chrome_setup
      require_relative 'server_cdp'

      @uuid = SecureRandom.uuid
      @chrome_pid = UI_CDP.setup_chrome(@local_addr.inspect_sockaddr, @uuid)
      DEBUGGER__.warn <<~EOS
        With Chrome browser, type the following URL in the address-bar:

           devtools://devtools/bundled/inspector.html?v8only=true&panel=sources&noJavaScriptCompletion=true&ws=#{@local_addr.inspect_sockaddr}/#{@uuid}

        EOS
    end