# File lib/webrick/httpproxy.rb, line 169
    def proxy_connect(req, res)
      # Proxy Authentication
      proxy_auth(req, res)

      ua = Thread.current[:WEBrickSocket]  # User-Agent
      raise HTTPStatus::InternalServerError,
        "[BUG] cannot get socket" unless ua

      host, port = req.unparsed_uri.split(":", 2)
      # Proxy authentication for upstream proxy server
      if proxy = proxy_uri(req, res)
        proxy_request_line = "CONNECT #{host}:#{port} HTTP/1.0"
        if proxy.userinfo
          credentials = "Basic " + [proxy.userinfo].pack("m*")
          credentials.chomp!
        end
        host, port = proxy.host, proxy.port
      end

      begin
        @logger.debug("CONNECT: upstream proxy is `#{host}:#{port}'.")
        os = TCPSocket.new(host, port)     # origin server

        if proxy
          @logger.debug("CONNECT: sending a Request-Line")
          os << proxy_request_line << CRLF
          @logger.debug("CONNECT: > #{proxy_request_line}")
          if credentials
            @logger.debug("CONNECT: sending a credentials")
            os << "Proxy-Authorization: " << credentials << CRLF
          end
          os << CRLF
          proxy_status_line = os.gets(LF)
          @logger.debug("CONNECT: read a Status-Line form the upstream server")
          @logger.debug("CONNECT: < #{proxy_status_line}")
          if %r{^HTTP/\d+\.\d+\s+200\s*} =~ proxy_status_line
            while line = os.gets(LF)
              break if /\A(#{CRLF}|#{LF})\z/om =~ line
            end
          else
            raise HTTPStatus::BadGateway
          end
        end
        @logger.debug("CONNECT #{host}:#{port}: succeeded")
        res.status = HTTPStatus::RC_OK
      rescue => ex
        @logger.debug("CONNECT #{host}:#{port}: failed `#{ex.message}'")
        res.set_error(ex)
        raise HTTPStatus::EOFError
      ensure
        if handler = @config[:ProxyContentHandler]
          handler.call(req, res)
        end
        res.send_response(ua)
        access_log(@config, req, res)

        # Should clear request-line not to send the sesponse twice.
        # see: HTTPServer#run
        req.parse(NullReader) rescue nil
      end

      begin
        while fds = IO::select([ua, os])
          if fds[0].member?(ua)
            buf = ua.sysread(1024);
            @logger.debug("CONNECT: #{buf.size} byte from User-Agent")
            os.syswrite(buf)
          elsif fds[0].member?(os)
            buf = os.sysread(1024);
            @logger.debug("CONNECT: #{buf.size} byte from #{host}:#{port}")
            ua.syswrite(buf)
          end
        end
      rescue => ex
        os.close
        @logger.debug("CONNECT #{host}:#{port}: closed")
      end

      raise HTTPStatus::EOFError
    end