Installed iPerf3 on Windows (10) to c:\program files\iPerf. When attempting to connect to a server, was receiving the error: “iperf3: error – unable to create a new stream: Permission denied”.
Couldn’t find anything Windows-related by searching.
The problem was that attempting to run in a protected location (“c:\program files”) blocked the program from being able to create temporary files. Relocating and running from a non-protected location fixed the problem.