Another app or another Mendix app running in the background for unknown reasons is using port 8080. You can

1. Open localhost:8080 in the browser to see whether this is a correct and running app serving html pages.
2. Stop the other mendix app if you know one
3. Log out and try again if it is another Mendix app in the background that did not end correctly
4. Change the port in settings/configuration, make it 8081 and 8091 for example

What Chris says. But if you want to use 8080, first kill the proces running on port 8080. To do that, open a command prompt and get the list of processes by the netstat command, than kill the process:

netstat -ano |find "8080"

taskkill -f -PID <pidnumber>

Hi Rayvandi,

Try to change the port 

1) Application settings ->Server -> change the port 8081 or 8082 like this.

2)Check any other application server is running or not if yes stop the server.

3) Open Task Manager 

Search jdk check there is any existing jdk or not if yes then kill them by right clicking on that jdk.

Hope you like the answer.