Kill already running ports with ease

One of the most annoying things during development is the moment we face the following error in command line while trying to launch an application locally:

Server Error: this port is already in use

Most of the times this means that we have forgotten a process running in the background or that we thought that we killed a process but we actually didn't, since we didn't use CTRL + C to kill it the right way etc

This is probably the moment that most developers start searching around the web to find a solution so the marathon for copy-n-pasting random commands in terminal begins 🙈

# A common approach

On a Linux / Mac machine, this might save the day for you:

lsof -ti tcp:[PORT] | xargs kill

Let's break this into steps to understand some more what is going on here:

• lsof is used to List Open Files so we can spot processes that listen on a specific port
• -i is used to search for the wanted port
• -t is used to return only the PID (process id) we are looking for
• | is used to pass the list of PID we found, to the next command
• xargsis used to apply kill to each of these PID
• kill is actually killing each PID. We might need to use kill -9 if processes need to be killed by force

But, who can memorize all these, right? 😬

# An easier approach

Let's see an even more straightforward solution we can use:

# One port
npx kill-port [PORT]

# Multiple ports
npx kill-port [PORT1] [PORT2] [PORTN]

Easier, right? By doing so, we pull the npm package kill-port so it can do the dirty work for us.

It is far more declarative and self-explanatory so it is definitely easier to remember.

Cheers!!