Github user zentol commented on the issue:
https://github.com/apache/flink/pull/4586
So I went back to configuring a single port, starting a flink cluster (JM +
2 TM) and 1 HTTPServer in the IDE.
Starting the HTTPServer in the IDE before the cluster does in fact lead to
an IOException in the reporters.
Starting the cluster before the HTTPServer leads to an exception in the IDE.
But if i only start the cluster the reporters start up without an exception.
This may be an OS issue, in particular the Windows10 WSL feature. I'll try
it again later on a linux machine; if it works there I'll merge this.
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