暂时仅支持HTTP
var request = (HttpWebRequest)WebRequest.Create(url); //Create:创建WebRequest对象
//HttpWebResponse对象实例:该类用于获取和操作HTTP应答 var可改成HttpWebResponse
var response = (HttpWebResponse)request.GetResponse(); //GetResponse:获取答复
//构造数据流对象实例
Stream stream = response.GetResponseStream();//GetResponseStream:获取应答流
StreamReader sr = new StreamReader(stream); //从字节流中读取字符
