I know that many methods have already come out as solutions. However, as you can see in the picture, when I search for port 3000 in 'cmd', the process in use does not appear. In the case of 8080, it comes out well because the Spring Boot server is running, but in the case of 'React', even if there is no process using port 3000 as shown in the picture, 'Something is already running on port 3000'. is printed out.

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I'm using a translator so it might be difficult to understand, but any help would be appreciated.

CodePudding user response：

Have you tried:

Running cmd as admin

Using :3000 instead of 3000

taskkill /PID <PID> /F kills the process, just replace with the PID, to the right of "listening".

If none works, you could just restart the pc.

NOTE: some people have encountered this error even after restarting, but managed to solve the problem with this command: npx kill-port 3000

CodePudding user response：

This means you have launched another instance before... Switching off the computer can work but there is another solution In windows, just open the Ressource Monitor (Task Manager -> Performance ->Open Ressource Monitor) then open the Listening port and check if 3000 is already running