EADDRINUSE gets generated on every save with Nodemon

Question

I use Ubuntu 20.04, Nodemon 2.0.4, Node 14.9.0 and Express 4.17.1. Every time I save my code I get this error:

events.js:291
      throw er; // Unhandled 'error' event
      ^

Error: listen EADDRINUSE: address already in use :::3000
    at Server.setupListenHandle [as _listen2] (net.js:1318:16)
    at listenInCluster (net.js:1366:12)
    at Server.listen (net.js:1452:7)
    at Function.listen (/home/ubuntu/kopum/node_modules/express/lib/application.js:618:24)
    at Object.<anonymous> (/home/ubuntu/kopum/app.js:37:5)
    at Module._compile (internal/modules/cjs/loader.js:1075:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1096:10)
    at Module.load (internal/modules/cjs/loader.js:940:32)
    at Function.Module._load (internal/modules/cjs/loader.js:781:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:72:12)
    at internal/main/run_main_module.js:17:47
Emitted 'error' event on Server instance at:
    at emitErrorNT (net.js:1345:8)
    at processTicksAndRejections (internal/process/task_queues.js:80:21) {
  code: 'EADDRINUSE',
  errno: -98,
  syscall: 'listen',
  address: '::',
  port: 3000
}
[nodemon] app crashed - waiting for file changes before starting...

And then I try to run this on terminal:

sudo lsof -i :3000
kill -9 {PID}

Then I restart the Nodemon by running nodemon app.js and everything's back to normal. But the EADDRINUSE is back again when I add some code and save it.

Answer 1

A simple fix that worked when I had a similar issue is to delay Nodemon's restart slightly:

nodemon --delay 500ms app.js

This seems to give a little time for ports to be correctly released.

Answer 2

Seems like nodemon does not correctly kill child-spawn processes before start;

Edit the scripts attribute in your package.json file and add a kill command to terminate any processes listening on your port before the server starts.

"scripts": {
    "start": "npm run kill && nodemon app.js",
    "kill": "kill -9 $(lsof -i :3000) &>/dev/null | exit 0"
}

Answer 3

尝试在每次保存命令后运行 npx kill-port 3000