Connect_Parallel_FailsOver Assert.NotNull() test failure

[MihaZupan]

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1599506
Build error leg or test failing: System.Net.Sockets.Tests.SocketAsyncEventArgsTest.Connect_Parallel_FailsOver
Pull request: #133058

Error Message

System.Net.Sockets.Tests.SocketAsyncEventArgsTest.Connect_Parallel_FailsOver(preferIPv6: True) [FAIL]
  Assert.NotNull() Failure: Value is null
  Stack Trace:
    /_/src/libraries/System.Net.Sockets/tests/FunctionalTests/SocketAsyncEventArgsTest.cs(1183,0): at System.Net.Sockets.Tests.SocketAsyncEventArgsTest.Connect_Parallel_FailsOver(Boolean preferIPv6)
    /_/src/mono/System.Private.CoreLib/src/System/Reflection/MethodBaseInvoker.Mono.cs(22,0): at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Method(Object obj, IntPtr* args)
    /_/src/libraries/System.Private.CoreLib/src/System/Reflection/MethodBaseInvoker.cs(174,0): at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(Object obj, Span`1 copyOfArgs, BindingFlags invokeAttr)

DO NOT USE JSON BELOW IF THIS IS A BUILD BREAK otherwise build analysis will allow pull requests to merge that break the build worse. For a build break, do not use this issue form. Make a regular new issue.

Fill the error message using step by step known issues guidance.

{
  "ErrorMessage": ["Connect_Parallel_FailsOver(preferIPv6: True) [FAIL]", "Assert.NotNull() Failure: Value is null"],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1599506
Error message validated: [Connect_Parallel_FailsOver(preferIPv6: True) [FAIL] Assert.NotNull() Failure: Value is null]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 9/16/2026 9:22:32 PM UTC

Report

Build	Repository	Test	Pull Request
1613860	dotnet/runtime	System.Net.Sockets.Tests.SocketAsyncEventArgsTest.Connect_Parallel_FailsOver	#134699
1602193	dotnet/runtime	System.Net.Sockets.Tests.SocketAsyncEventArgsTest.Connect_Parallel_FailsOver	#133360
1600037	dotnet/runtime	System.Net.Sockets.Tests.SocketAsyncEventArgsTest.Connect_Parallel_FailsOver	#134105
1599506	dotnet/runtime	System.Net.Sockets.Tests.SocketAsyncEventArgsTest.Connect_Parallel_FailsOver	#133058

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	0	4

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[MihuBot]

I'm a bot. Here is a possible related and/or duplicate issue (I may be wrong):

• Android socket tests failing with IPv6 connectivity issues #127422