default port is not working when developing locally

[zkurzyns]

According to README, this command
npm run-script server
Should start a server instance and begin listening for connections at http://localhost:8080

It looks like it doesn't work.
When I launch that command the serwer runs on some random ports.

Adding an option --port 8080 in package.json forces 8080 port usage.

"server": "webpack-dev-server --history-api-fallback --inline --progress --devtool source-map --mode development --port 8080"

I am not sure if this is my env problem, can any one confirm it?