c# Why does System.net.WebException happen

Question

Preconditions:

The code is as follows:

ServicePointManager.ServerCertificateValidationCallback += (s, cert, chain, sslPolicyErrors) => true;

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls | SecurityProtocolType.Ssl3;

using (WebClient client = new WebClient())

{

。。。。。。

IWebProxy proxy = Proxy.GetWebProxy(new Uri(address));

。。。。。。

byte[] resBytes = client.UploadValues(address, param);

}

abnormal：

The following fault occurs, but it does not occur every time it runs, it only occasionally occurs:

System.Net.WebException:

Connection disconnected: the connection that was needed to be cut was disconnected by the server.

• system. Io.ioexception: unable to read data from a transfer connection: unable to connect because the connected caller did not respond correctly even after a certain period of time. The established connection failed because the connected host did not respond.

• system. Net. Sockets. Socketexception: unable to connect because the connected caller did not respond correctly even after a certain period of time. The established connection failed because the connected host did not respond.

question：

What is the cause of the malfunction

Answer 1

Can no one answer this question？