Error: Port XXXX is already in use. Use --port to specify a different port.When I tried to run the ng-serve command

👤 Diwas Poudel    🕒 16 Mar 2019    📁 FIX

 When I tried to run the "ng-serve" command again it gives me "Port 4200 is already in use."

What is Port Number and how problems arise?

Actually the port number is used to find particular applications in a network. Sometimes two application tries to use the same port. Suppose Application A  is using port XXXX then when another application says Application  B tries to use the same port number then the above problem may arise. Here I am using port XXXX as Port 4200.


For Windows User

Method 1: 

So, in this method, we have to kill the process running on this port and again reuse that port.So lets start

Step1: Open cmd and type as below

check which port is used

Here we can see Port 4200 is used by Process ID: 12868  as we have status as LISTENING so we must kill a process running on this PID

Step2: Forcefully Killing Process ID  12868  as shown below

killing process

Step 3: Now you can do "ng-serve" to start your angular app at the same port 4200

Method 2:

Try using another port to serve the current angular project.

ng serve --port 12012

Here I have specified port number 12012. But this is not best practice because here each time i am doing ng serve I have to use different cases. So this is just an alternative solution but doesn't use it.


For Linux User

First, open a terminal and kill the process 4200 as shown below:

sudo kill `sudo lsof -t -i:4200`

This will kill all processes running at post number 4200 and your angular project will run now.