HttpWebRequest creates many connections

[MhdTlb]

Steps to reproduce

1. Create a Class Library project and make target frameworks net462 and netstandard2.0.
2. Add a new class to the project with following code:

        public class Httpwebrequesttest
	{
              public static void Run()
              {
                  for (int i = 0; i < 1000; i++)
                  {
                      var client = WebRequest.CreateHttp("http://localhost:80");
                      using (var res = client.GetResponse())
                      {
      
                      }
                      Console.WriteLine($"{i}");
                  }
                  Console.WriteLine($"press enter then exit");
                  Console.ReadLine();
              }
          }

3. Add Console project to the solution and make target framework as netcoreapp3.1
4. Add the Class library project as dependency to the Console App and call the Httpwebrequesttest.Run method from the Console App
5. Open a CMD and run this command netstat -na | find "80"

Expected behavior

I was expecting to see few TCP connections but there are hundreds of them with the TIME_WAIT status:
... TCP [::1]:63056 [::1]:80 TIME_WAIT ...

If I change the target framework of the Console Application to net462 and I run the netstat command, i can see few TCP connections with status ESTABLISHED

Notes

• I tried to play with ServicePointManager.DefaultConnectionLimit in the Class Library project but it did not help
• Also, I changed connectionManagment.maxConnection(https://docs.microsoft.com/en-us/dotnet/framework/configure-apps/file-schema/network/connectionmanagement-element-network-settings?redirectedfrom=MSDN) in App.config file without luck

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Issue Details

---

Steps to reproduce

1. Create a Class Library project and make target frameworks net462 and netstandard2.0.
2. Add a new class to the project with following code:

        public class Httpwebrequesttest
	{
              public static void Run()
              {
                  for (int i = 0; i < 1000; i++)
                  {
                      var client = WebRequest.CreateHttp("http://localhost:80");
                      using (var res = client.GetResponse())
                      {
      
                      }
                      Console.WriteLine($"{i}");
                  }
                  Console.WriteLine($"press enter then exit");
                  Console.ReadLine();
              }
          }

3. Add Console project to the solution and make target framework as netcoreapp3.1
4. Add the Class library project as dependency to the Console App and call the Httpwebrequesttest.Run method from the Console App
5. Open a CMD and run this command netstat -na | find "80"

Expected behavior

I was expecting to see few TCP connections but there are hundreds of them with the TIME_WAIT status:
... TCP [::1]:63056 [::1]:80 TIME_WAIT ...

If I change the target framework of the Console Application to net462 and I run the netstat command, i can see few TCP connections with status ESTABLISHED

Notes

• I tried to play with ServicePointManager.DefaultConnectionLimit in the Class Library project but it did not help
• Also, I changed connectionManagment.maxConnection(https://docs.microsoft.com/en-us/dotnet/framework/configure-apps/file-schema/network/connectionmanagement-element-network-settings?redirectedfrom=MSDN) in App.config file without luck

Author:	MhdTlb
Assignees:	-
Labels:	area-System.Net, untriaged
Milestone:	-

[ManickaP]

Should be fixed in dotnet/corefx#41462 which went into 5.0. If you switch to .NET 5.0 do you still see this problem?

In .NET Core WebRequest is based on HttpClient, so that's why it has such a different behavior from .NET Framework. We do recommend to switch from WebRequest to HttpClient if you plan to target .NET Core and .NET 5.0+ runtimes.

[MhdTlb]

@ManickaP .Net5.0 does not have the issue

[ManickaP]

@MhdTlb thanks for the confirmation.

How much is the issue impacting you? And would you be able to upgrade to .NET 5.0 (or 6.0 which is RC1 now)?

[karelz]

Triage: Addressed in 5.0+. Closing.

[MhdTlb]

@ManickaP Unfortunately, we can not upgrade to .NET 5.0 right now. Is there a workaround to keep using 3.1?

[karelz]

@MhdTlb there is no workaround to our best knowledge. Why cannot you upgrade to .NET 5.0 now? What limits you?
If you need LTS, did you consider .NET 6.0? (it is now in RC1 which has go-live license, with GA following soon in November)

[ManickaP]

@MhdTlb you'd need use HttpClient and cache it yourself.