Eclectic Saddlebag

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Kill Blocked Ports

July 22, 2019

So you are working hard on your new Gatsby site and fire up the development server.

FAIL!. You are presented with the console error message:

Something is already running at port 8000
Would you like to run the app at another port instead? [Y/n]

The cause is that a process did not fully close, or you terminated a terminal window without exiting the command.

What To Do

FYI. The fix below is geared toward MacOS or Ubuntu/Linux. It might work on Windows.

The workaround is simple.

  • Exit the startup.
  • Enter the following at the command prompt:

kill -9 $(lsof -t -i:8000)

Cool all fixed. But, do you want to search out this command every time this happens?

NO, of course not.

Solution: Create a command alias in your favorite terminal. In ZSH open your zshrc file and add the following alias: alias k8="kill -9 $(lsof -t -i:8000)"

Now, the next time this happens, escape out of the develop script and enter k8. All done.

All fixed, sort of.

The alias command only responds to one situation, and one port number. What about the Gatsby serve command (port 9000), or Create-React-App (port 3000)? You will have to create an alias for each situation. There has to be a more productive way.

The answer is to create a shell script. Create the below script:

#!/bin/bash
#styles
VP_RED='\033[01;31m'
# Update default core install
echo -e "${VP_RED}KILLING the SPECIFIED PORT"
kill $(lsof -t -i:$1)

A couple of note:

  • The styles line VP_RED='\033[01;31m' only makes the command red in the terminal window.
  • The echo line initiates the style.
  • The most import part is the last line, which is the command that kills the port.
  • The name of the file will be the command you type. In my case, kport.
  • Make this file executable: chmod +x kport
  • Place in the user’s path.

In my case, I have added to /bin and named the file kport. So, when you execute the file, remember to include a port number which you want to kill, as an argument (i.e.): kport 8000

DONE! I hope this helps. Have a great day.