how to resolve "EADDRINUSE" error and "Proxy error"? - node.js

Question

I have two problems when running my NPM. The first problem is whenever I save my files. I get this error message.
Also when I make a request to the server from my frontend. I get the proxy error message
This is my scripts in my package.json for my backend
"scripts": {
"client": "npm start --prefix client",
"server": "node app.js --ignore client",
"start": "npm start --prefix client",
"dev": "concurrently \"npm run server\" \"npm run client\"",
"test": "echo \"Error: no test specified\" && exit 1"
},
And also my package.json for my client as you can see below
{
"name": "client",
"version": "0.1.0",
"private": true,
"proxy": "http://localhost:5000",
"dependencies": {
"#fortawesome/fontawesome-svg-core": "^1.2.8",
"#fortawesome/free-brands-svg-icons": "^5.6.3",
"#fortawesome/free-solid-svg-icons": "^5.5.0",
"#fortawesome/react-fontawesome": "^0.1.3",
"axios": "^0.19.0",
"react": "^16.10.2",
"react-dom": "^16.10.2",
"react-router-dom": "^5.1.2",
"react-scripts": "3.2.0",
"react-spring": "^8.0.27"
},
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test",
"eject": "react-scripts eject"
},
"eslintConfig": {
"extends": "react-app"
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
},
"devDependencies": {
"node-sass": "^4.12.0"
}
}

Answer 1

Assuming you're on windows:
Run netstat -aon to view the processes running on each port
Find the process running on 0.0.0.0:5000 or 127.0.0.1:5000 and note its PID
Run taskkill /F /PID <pid_number> to kill that process
You should now be able to run your npm service on that port
If you're on Linux or Mac you should be able to follow the same process, just google what the commands are called on those OSs

Answer 2

EADDRINUSE tells you, port 5000 is already open by another process or the same process. So either something else is running on the port, or in your case it is more likely your app doesn't close the port properly when restarting.
You can manually force close the process and restart it, but that can be quite a pain, instead of restarting when you save. Since you probably want the latter.
So I'd suggest looking at your code and check for things that could prevent your app from shutting down, or delay your shut down. So Pay attention to things such as promises that have not resolved yet, and timeouts that are still running.
As for your proxy issue you get a ECONNRESET, which basically says your connection has been shut down by the peer (so the proxy in your case), most likely because port 5000 gets shutdown and restarted. I reckon that one will be solved once you resolve your first issue.
Hope this helps with resolving your issue.