MEAN Cookbook

Tips for resolving port collision

Port collision is a problem that can happen when the port you are attempting to run your app on is already in use:

Port 4200 is already in use. Use '--port' to specify a different port.

This often happens if you accidentally leave open a previous instance of your application while trying to start another. On Unix systems, you can find and kill orphaned processes using the ps and grep commands:

ps aux | grep angular

This will return a process list you can consult to find your rogue Angular-CLI process:

nmcclay    88221   0.0  1.8  3398784 296516   ??  S     7:56PM   0:12.59 @angular/cli

Now that you have found your process, you can stop it with the kill command:

Kill 88221

Another common cause of this error can be running ...