workman 如果要统计 收发的流量情况，改怎么统计？

<?php
namespace app\middleware;

use Webman\MiddlewareInterface;
use Webman\Http\Response;
use Webman\Http\Request;

class Network implements MiddlewareInterface
{
    public function process(Request $request, callable $next) : Response
    {
        // http请求字节数
        echo strlen($request->rawBuffer())."\n";
        $response = $next($request);
        // http响应字节数
        echo strlen($response)."\n";
        return $response;
    }
}