HttpWebRequest中GetResponse或者说GetRequestStream偶尔超时，或者是各种操作超时造成的假死的一些解决方案

今天用了将近一天的时间来查找这个问题的存在，不停的百度查找原因测试原因，发现解决方案很是简单，不过最好还好哦啊都解决了，在这里纪录一下，希望可以帮到你们

 payload = System.Text.Encoding.UTF8.GetBytes(postDataStr);
                request.ContentLength = payload.Length;
                Stream writer = request.GetRequestStream();
                writer.Write(payload, 0, payload.Length);
                //writer.Flush();
                writer.Close();
                //HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                HttpWebResponse res;
                try
                {
                    System.Net.ServicePointManager.DefaultConnectionLimit = 200;
                    res = (HttpWebResponse)request.GetResponse();
                }
                catch (WebException ex)
                {

                    res = (HttpWebResponse)ex.Response;
                }

 今天我的res 一直报操作超时，百度了很多方案，一一测试，总结来说，如果你也出现了这种错误，可以一次尝试一下方案

第一种：加长request的timeout的时间，默认是100秒（我就是测试了好多方案，才发现我的timeout的时间太短，引起的操作超时）

第二种：设置request.KeepAlive = false;原因是：默认KeepAlive的属性是true，将此属性设置为 true 以发送带有 Keep-alive 值的 Connection HTTP 标头。 应用程序使用 KeepAlive 指示持久连接的首选项。 当 KeepAlive 属性为 true 时，应用程序与支持它们的服务器建立持久连接。也要记住要及时关闭相对应的关闭工作

if (request != null)
                {
                    request.Abort();
                }
                if (res != null)
                {
                    res.Close();
                }

第三种：

System.Net.ServicePointManager.DefaultConnectionLimit = 200;

 加上这句话，因为这个默认设置的是2，当http的连接超过2条时，也会报这种操作超时的错误

第四种：

                System.GC.Collect();
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
                request.Method = "POST";
                request.ContentType = "application/x-www-form-urlencoded";
                request.ContentLength = postDataStr.Length;
                request.KeepAlive = false;
                request.Timeout = 6000000;

 在

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);

 之前加上：System.GC.Collect();

原因是：系统中的http相关的资源没有正确的释放，导致后续的GetResponse或者说GetRequestStream超时死掉

    改进之后的所有代码：

public static bool HttpPost(string Url, string postDataStr, out string errMsg, out string returnData)
        {
            try
            {
                System.GC.Collect();
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
                request.Method = "POST";
                request.ContentType = "application/x-www-form-urlencoded";
                request.ContentLength = postDataStr.Length;
                request.KeepAlive = false;
                request.Timeout = 6000000;
                //StreamWriter writer = new StreamWriter(request.GetRequestStream(), Encoding.UTF8);
                //writer.Write(postDataStr);
                //writer.Flush();
                byte[] payload;
                payload = System.Text.Encoding.UTF8.GetBytes(postDataStr);
                request.ContentLength = payload.Length;
                Stream writer = request.GetRequestStream();
                writer.Write(payload, 0, payload.Length);
                //writer.Flush();
                writer.Close();
                //HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                HttpWebResponse res;
                try
                {
                    System.Net.ServicePointManager.DefaultConnectionLimit = 200;
                    res = (HttpWebResponse)request.GetResponse();
                }
                catch (WebException ex)
                {

                    res = (HttpWebResponse)ex.Response;
                }
                
              
                //StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
                StreamReader reader = new StreamReader(res.GetResponseStream(), Encoding.UTF8);
                string retString = reader.ReadToEnd();
                errMsg = "";
                try
                {
                    returnData = Util.base642Str(retString);
                }
                catch (Exception)
                {
                    returnData = retString;
                    //throw;
                }
                if (request != null)
                {
                    request.Abort();
                }
                if (res != null)
                {
                    res.Close();
                }
                return true;
            }

                       参考文章：https://www.cnblogs.com/wohexiaocai/p/5673193.html