How can I find what's using a port and free it up without restarting?

[TylerJW]

I’m trying to set up a local development environment for a web project, and I keep hitting a wall with port conflicts. Every time I run my node server, something else seems to be blocking the port I need, and I’m not sure how to properly identify what’s using it or free it up without restarting my machine.

[Kenneth.G]

I had this last week. I ran sudo lsof -i -P -n | grep LISTEN to see who owned it, got PID 12345, and killed that process. Then I started the server again and it came up in about 2 seconds.

[LoganSP]

I found the culprit by running sudo lsof -i :3000 and saw a node process, killed it, and then reran. The port freed up, and the server started fine.

[MilaVP]

Maybe the problem isn't the port at all. My watcher kept restarting the app, which looked like a block but was just a crash loop.

[Abigail_G]

I tried changing the number and saw it bite again; maybe it's the proxy in front of the dev server acting up or a hot reload stubbornly taking sockets.