c# https请求

　　遇到Https网站，c# http请求的时候，总是报SSL连接错误。后来经搜索，发现有解决方案：

.net 2.0  需要引入一个第三方组件：BouncyCastle.dll，这是我写的一个例子：

        public static string RequestWebServerByTCP(Uri uri, string method, NameValueCollection parameter, string cookie, Encoding encoding)
        {
            try
            {
                StringBuilder RequestHeaders = new StringBuilder();

                RequestHeaders.Append(method + " " + uri.PathAndQuery + " HTTP/1.1\r\n");

                method = method.ToUpper();

                if (method == POSTMETHOD)
                    RequestHeaders.Append("Content-Type:application/x-www-form-urlencoded\r\n");
                RequestHeaders.Append("User-Agent:Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.64 Safari/537.11\r\n");
                RequestHeaders.Append("Cookie:" + cookie + "\r\n");
                RequestHeaders.Append("Accept:*/*\r\n");
                RequestHeaders.Append("Host:" + uri.Host + "\r\n");

                byte[] postdata = null;
                StringBuilder sb = new StringBuilder();

                if (method == GETMETHOD)
                {
                    uri = GetMethodQueryString(uri, parameter, encoding);
                }
                else if (method == POSTMETHOD)
                {
                    if (parameter != null)
                    {
                        foreach (string key in parameter)
                        {
                            sb.Append(string.Format(FORMATSTR1, System.Web.HttpUtility.UrlEncode(key, encoding), System.Web.HttpUtility.UrlEncode(parameter[key], encoding)));
                        }
                    }
                    if (sb.Length != )
                    {
                        sb = sb.Remove(sb.Length - , );
                    }
                    postdata = encoding.GetBytes(sb.ToString());

                    RequestHeaders.Append("Content-Length:" + postdata.Length + "\r\n");
                }

                RequestHeaders.Append("Connection:close\r\n\r\n");
                byte[] req = Encoding.UTF8.GetBytes(RequestHeaders.ToString() + sb.ToString());

                int port = ;

                MyTlsClient client = new MyTlsClient();
                var protocol = OpenTlsConnection(uri.Host, port, client);

                Stream tlsStream = protocol.Stream;
                tlsStream.Write(req, , req.Length);
                tlsStream.Flush();

                StreamReader reader = new StreamReader(tlsStream);

                String line;
                StringBuilder html = new StringBuilder();

                string firstLine = "";

                int i = ;

                while ((line = reader.ReadLine()) != null)
                {
                    if (i == )
                    {
                        firstLine = line;
                        i++;
                    }

                    html.AppendLine(line);

                    if (line.Contains("</html>"))
                    {
                        break;
                    }
                }
                protocol.Close();

                string httpstatusCode = "";

                string[] httpstatus = firstLine.Split(new string[] { " " }, StringSplitOptions.RemoveEmptyEntries);
                if (httpstatus.Length > )
                {
                    httpstatusCode = httpstatus[];
                }
                else
                {
                    //请求无效
                    httpstatusCode = "";
                }
                return html.ToString();

            }
            catch
            {
                return "";
            }

        }

　　请求到的html，为什么需要一行一行读呢？我在调试的时候发现有个bug，如果一次性读取的时候，它停不下来，最终报错，所以我做了一个读到html末尾的判断。

继承了提供的默认类：

  class MyTlsClient : DefaultTlsClient
    {
        public override TlsAuthentication GetAuthentication()
        {
            return new MyTlsAuthentication();
        }
    }

    // Need class to handle certificate auth
    class MyTlsAuthentication : TlsAuthentication
    {
        public TlsCredentials GetClientCredentials(CertificateRequest certificateRequest)
        {
            // return client certificate
            return null;
        }

        public void NotifyServerCertificate(Certificate serverCertificate)
        {
            // validate server certificate
        }
    }

       internal static TlsClientProtocol OpenTlsConnection(string hostname, int port, TlsClient client)
        {
            TcpClient tcp = new TcpClient(hostname, port);

            TlsClientProtocol protocol = new TlsClientProtocol(tcp.GetStream(), secureRandom);
            protocol.Connect(client);
            return protocol;
        }

拼接url参数的方法：

      private static Uri GetMethodQueryString(Uri uri, NameValueCollection parameter, Encoding encoding)
        {
            List<KeyValuePair<string, string>> parameter1 = new List<KeyValuePair<string, string>>();
            foreach (string key in parameter)
            {
                parameter1.Add(new KeyValuePair<string, string>(key, parameter[key]));
            }
            return GetMethodQueryString(uri, parameter1, encoding);
        }

        private static Uri GetMethodQueryString(Uri uri, List<KeyValuePair<string, string>> parameter, Encoding encoding)
        {
            string format = string.Empty;
            UriBuilder uribuilfer = new UriBuilder(uri);

            string QueryString = string.Empty;
            if (string.IsNullOrEmpty(uribuilfer.Query))
            {
                format = FORMATSTR1;
            }
            else
            {
                format = FORMATSTR2;
            }
            QueryString = uribuilfer.Query;
            if (parameter != null)
            {
                foreach (KeyValuePair<string, string> item in parameter)
                {
                    QueryString += string.Format(format, System.Web.HttpUtility.UrlEncode(item.Key, encoding), System.Web.HttpUtility.UrlEncode(item.Value, encoding));
                }
            }
            QueryString = QueryString.TrimEnd(new char[] { '&' });
            QueryString = QueryString.TrimStart(new char[] { '?' });
            uribuilfer.Query = QueryString;
            uri = uribuilfer.Uri;
            return uri;
        }

　　注意：List<KeyValuePair<string, string>>和NameValueCollection类型的参数有什么区别呢？它们都包含相同的key，只不过存储的时候，NameValueCollection会把含有相同Key的值用逗号隔开，存在一起。这样请求有可能会失败，拿不到数据。本人因此问题，折腾了很久，用python实现了请求，后来在.net core中实现了一遍，最后终于低下了高傲的头颅，才看到传参时候，有点问题。

.net  4.0中，只需要添加一句话：ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;

       .net 4.5中，什么都不用管。

2.0中连TCP都用上了，不过我们看到了http请求的本质，把一段具有格式的请求头+请求数据转为二进制发送到主机的某个端口，返回流，通过读取流，就可以拿到结果。

说到这，我们来看看Request消息格式：

GET https://www.baidu.com/ HTTP/1.1
Accept: text/html, application/xhtml+xml, */*
Accept-Language: zh-CN
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko
Accept-Encoding: gzip, deflate
Connection: Keep-Alive
Host: www.baidu.com
Cookie: BAIDUID=C1EFC3A3466AAAEBE74C6F6E7F413FA8:FG=1; BIDUPSID=C1EFC3A3466AAAEBE74C6F6E7F413FA8; PSTM=1525339270; BD_LAST_QID=12260391193367555241

1、请求行，包含请求的方法，url，http协议版本

2、请求头，接收的格式，浏览器代理，cookie等等

3、空行

4、请求体，传递数据

Response格式：

HTTP/1.1 200 OK
Bdpagetype: 1
Bdqid: 0x9a1ff959000016d0
Cache-Control: private
Connection: Keep-Alive
Content-Encoding: gzip
Content-Type: text/html; charset=utf-8
Cxy_all: baidu+77e5655ffd82ce31adf5edff251fc585
Date: Thu, 03 May 2018 09:21:10 GMT
Expires: Thu, 03 May 2018 09:21:03 GMT
Server: BWS/1.1
Set-Cookie: BDSVRTM=0; path=/
Set-Cookie: BD_HOME=0; path=/
Set-Cookie: H_PS_PSSID=1428_21080_20719; path=/; domain=.baidu.com
Strict-Transport-Security: max-age=172800
Vary: Accept-Encoding
X-Powered-By: HPHP
X-Ua-Compatible: IE=Edge,chrome=1
Transfer-Encoding: chunked

html

1、状态行

2、消息报头，content-type,Date,Set-Cookie

3、空行

4、正文