ng serve --open reports port 4200 is already in use when it isn't

ng serve --open incorrectly reports that port 4200 is in use, even when no browsers are open.

Versions

Angular CLI: 1.6.7
Node: 8.9.4
OS: win32 x64
Angular: 5.2.3
... animations, common, compiler, compiler-cli, core, forms
... http, language-service, platform-browser
... platform-browser-dynamic, router

@angular/cli: 1.6.7
@angular-devkit/build-optimizer: 0.0.42
@angular-devkit/core: 0.0.29
@angular-devkit/schematics: 0.0.52
@ngtools/json-schema: 1.1.0
@ngtools/webpack: 1.9.7
@schematics/angular: 0.1.17
typescript: 2.5.3
webpack: 3.10.0

Repro steps

• ng new aatest1 -si
• cd aatest1
• npm install
• ng serve --open

Observed behavior

ps>ng serve --open
Port 4200 is already in use. Use '--port' to specify a different port.

Desired behavior

ng serve --open should work correctly

Mention any other details that might be useful (optional)

The above behavior did NOT occur with Angular-CLI 1.6.6 or earlier.

Work-around

specify --port 4216 (any value between 4200 and 4215 causes the above mentioned error)

[singhkeshav]

fuser -n tcp -k 4200 ng serve

[fmorriso]

ps>sl aaTest1
ps>ng serve --open
Port 4200 is already in use. Use '--port' to specify a different port.
ps>netstat -abno | out-file "$env:temp\aatest.txt" -Force -Width 1024 -encoding ASCII
ps>npp "$env:temp\aatest.txt"
ps>

I have attached the output from netstat. I cannot find anything that is listening on ports 4200 through 4215, the ones that no longer work as of Angular-CLI 1.6.7.

It’s as if the parsing of the default port number’s last two digits (00) is messed up because specifying port 4216 or above seems to work.

If I specify port 4201, for example, I still get the same error (port 4201 is in use):

ng serve --open --port=4201

Only ports 4216 and above work for me. Example:

ng serve --open --port=4216

aatest.txt