2.4 Put an app on your server

1. Install Node.js and pm2

sudo apt install nodejs npm -y
sudo npm install -g pm2

2. The app

mkdir ~/hello
cd ~/hello
nano app.js

Type this, then save (Ctrl + O, Enter) and exit (Ctrl + X):

const http = require("http");
http.createServer((req, res) => {
  res.end("Hello from my app on my own server");
}).listen(3000);

Test it on the server: node app.js, then in a second SSH window, curl http://localhost:3000. You'll see the line. Press Ctrl + C in the first window to stop it.

3. Keep it running with pm2

pm2 start app.js --name hello
pm2 save
pm2 startup

pm2 startup prints one command starting with sudo. Copy it, run it, then run pm2 save again. Now the app starts by itself after a restart.

4. Put nginx in front (once your domain points at the server, item 2.6)

sudo nano /etc/nginx/sites-available/hello

server {
    listen 80;
    server_name app.kwesibuilds.com;
    location / {
        proxy_pass http://localhost:3000;
    }
}

Use your own domain. Then turn it on, check it, and reload nginx:

sudo ln -s /etc/nginx/sites-available/hello /etc/nginx/sites-enabled/
sudo nginx -t
sudo systemctl reload nginx

nginx -t must say syntax is ok and test is successful before you reload. If it doesn't, open the file again and look for a missing ; or }.

Why port 3000 stays closed: the firewall only opens 22, 80 and 443. Visitors reach the app through nginx, never directly. Don't open extra ports unless you know why.