.NET5 HttpClient自定义服务器名称指定(SNI)的值

 

原理就是.NET5中SocketsHttpHandler类添加了一个属性ConnectCallback允许你自定义链接,但是假如你构造一个SslStream返回并且传入的uri是https协议那么库内部还会自动再套一个SslStream,所以后续传入的uri必须改成http协议

 

static async Task Main(string[] args)
        {
            const string DNS_AND_SNI = "www.pixivision.net";

            //注意这个地方是http而不是httpps
            //否则我们不能自定义sslstream
            const string URI = "http://www.pixiv.net/";

            var handler = new SocketsHttpHandler()
            {

                ConnectCallback = (info, token) =>
                {

                    Console.WriteLine(info.InitialRequestMessage.RequestUri);
                 
                    Socket socket = new Socket(SocketType.Stream, ProtocolType.Tcp);

                    socket.Connect(DNS_AND_SNI, 443);

                    var stream = new NetworkStream(socket, true);

                    SslStream sslstream = new SslStream(stream, false);

                    sslstream.AuthenticateAsClient(new SslClientAuthenticationOptions
                    {
                        //sni字符串
                        TargetHost = DNS_AND_SNI,

                        //tls指定后续的应用层协议
                        ApplicationProtocols = new List<SslApplicationProtocol>(new SslApplicationProtocol[] { SslApplicationProtocol.Http2 })
                    });


                    return new ValueTask<Stream>(sslstream);
                }
            };


            HttpClient client = new HttpClient(handler);

            //协议和tls预先指定的保持一致
            client.DefaultVersionPolicy = HttpVersionPolicy.RequestVersionOrHigher;
            client.DefaultRequestVersion = HttpVersion.Version20;
          
            var headers = client.DefaultRequestHeaders;

            headers.Add("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9");

            headers.Add("Accept-Language", "zh-CN,zh;q=0.9");

            headers.Add("User-Agent", "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.75 Safari/537.36");


            string s = await client.GetStringAsync(URI);

            Console.WriteLine(s.Length);
        }