Recently I am blocked by a very weird issue, from the VS installed machine, I can run performance testing which was distributed to multiple test agents successfully, but if try to run API testing, it is always failed, I have tried run in VS and also for commandline: both vstest.console and mstest, I am almost crashed by this tough guy:

Finally I found out the root cause, the VS machine's inbound connection in firewall setting is blocked, set it as allowed，the issue is gone.

The big difference between perf and API test run is that the firewall setting of VS machine .