intellij freezing on startup + putty routinely failing to bind to ports used for ssh tunneling

for the past few weeks i was plagued by putty randomly failing to bind to ports used for ssh tunneling giving me in its log “forwarding failed: Network error: Permission denied”

today my intellij failed to launch – it was freezing on the splash screen, C:\Users\xxxxxxxxxxxx\AppData\Local\JetBrains\IdeaIC2021.2\log\log.log had:

2021-10-20 11:32:47,562 [   9285]  ERROR - llij.ide.plugins.PluginManager - java.net.BindException: Address already in use: bind 
java.util.concurrent.CompletionException: java.net.BindException: Address already in use: bind
    at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:314)
    at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:319)
    at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1702)
    at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1692)
    at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
    at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
    at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
    at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
    at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)
Caused by: java.net.BindException: Address already in use: bind
    at java.base/sun.nio.ch.Net.bind0(Native Method)
    at java.base/sun.nio.ch.Net.bind(Net.java:455)
    at java.base/sun.nio.ch.Net.bind(Net.java:447)
    at java.base/sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:227)
    at io.netty.channel.socket.nio.NioServerSocketChannel.doBind(NioServerSocketChannel.java:134)
    at io.netty.channel.AbstractChannel$AbstractUnsafe.bind(AbstractChannel.java:562)
    at io.netty.channel.DefaultChannelPipeline$HeadContext.bind(DefaultChannelPipeline.java:1334)
    at io.netty.channel.AbstractChannelHandlerContext.invokeBind(AbstractChannelHandlerContext.java:506)
    at io.netty.channel.AbstractChannelHandlerContext.bind(AbstractChannelHandlerContext.java:491)
    at io.netty.channel.DefaultChannelPipeline.bind(DefaultChannelPipeline.java:973)
    at io.netty.channel.AbstractChannel.bind(AbstractChannel.java:260)
    at io.netty.bootstrap.AbstractBootstrap$2.run(AbstractBootstrap.java:356)
    at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:164)
    at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:472)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:500)
    at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
    at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    at java.base/java.lang.Thread.run(Thread.java:829)

that brought me to https://youtrack.jetbrains.com/issue/IDEA-238995 and workaroudn described there:

netsh int ipv4 set dynamicport tcp start=49152 num=16383
netsh int ipv4 set dynamicport udp start=49152 num=16383

net stop winnat
net start winnat

that did the trick – problems with intellij and tunneling in putty are gone! indeed, few weeks earlier i was playing with NAT for Hyper-V. before the change this command indeed was showing wide ranges of ports being reserved:

netsh interface ipv4 show excludedportrange protocol=tcp