HttpWebRequest request error, the underlying connection has been closed: The connection was closed unexpectedly

WIN10, C # executes a POST request with HttpWebRequest "request error, underlying connection closed: Connection closed unexpectedly", tested settings

Post request mode

           System.Net.HttpWebRequest request;
            request = (System.Net.HttpWebRequest) WebRequest.Create (strURL);
           //post Request Method
             request. Method = "POST";
            request. useragent = "mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2;. NET CLR 1.0.3705;) ";
           //content type
             request. ContentType = "application/x-www-form-urlencoded";
            request. KeepAlive = false; The
is not valid and finally found an add HTTP protocol, as follows

Request. ProtocolVersion = Httpversion.version10;

Successfully passed. The special record.

HttpWebRequest request error, the underlying connection has been closed: The connection was closed unexpectedly