an attempt was made to access a

看起来docker-for-win的副作用太大了

开发时监控2020端口时，应用提示试图打开一个禁止的socket端口。

相同问题，(解决方案](https://github.com/docker/for-win/issues/3171#issuecomment-459205576)

• netstat -ano检查此端口没有被使用
• Get-NetTCPConnection |findstr在powershell中也没发现此端口没占用
• Even if I disconnect from the internet and disable both windows firewall and my antivirus, and run everything as admin, I still get the errors.

还好我先google而不是先执行第三步操作。原因是windows默认排除了这些端口范围——

执行netsh interface ipv4 show excludedportrange protocol=tcp

D:\>netsh interface ipv4 show excludedportrange protocol=tcp

协议 tcp 端口排除范围

开始端口    结束端口
----------    --------
      1615        1714
      1715        1814
      1915        2014
      2015        2114
      7275        7374
     50000       50059     *

* - 管理的端口排除。

所以快捷解决方式就是不使用以上范围内的端口。

根本的解决方法如下。原因是Docker for Windows and Hyper-V are responsible for all of those excluded port ranges above.

• Disable hyper-v (which will required a couple of restarts)

dism.exe /Online /Disable-Feature:Microsoft-Hyper-V

• When you finish all the required restarts, reserve the port you want so hyper-v doesn't reserve it back

netsh int ipv4 add excludedportrange protocol=tcp startport=50051 numberofports=1

• Re-Enable hyper-V (which will require a couple of restart)

dism.exe /Online /Enable-Feature:Microsoft-Hyper-V /All