Serving on a custom port

Every site so far has used port 80, the default for http://. But nginx can listen on a custom port just as easily: 8080, 8000, 9000, anything free. This lesson shows how to set it with listen, why the port then shows up in the address bar, and how this differs from putting nginx in front of an app that runs on another port.

Change the port with listen

You already met listen in listen and server_name. To serve on a different port, just change the number:

server {
    listen 8080;
    server_name example.com;
    root /var/www/example;
    index index.html;
}

After nginx -t and a reload, the site answers on port 8080 instead of 80.

The port shows up in the URL

This is the part that surprises people. With listen 8080, the site is at:

http://example.com:8080

You have to type :8080. Here is why. A browser only assumes a port when you leave it out: :80 for http:// and :443 for https://. Any other port must be written in the address, or the browser goes to port 80 and finds nothing there.

So http://example.com (no port) still tries port 80. Only http://example.com:8080 reaches your block.

Listen on more than one port

A single server block can answer on several ports at once. Just list listen more than once:

server {
    listen 80;
    listen 8080;
    server_name example.com;
    root /var/www/example;
    index index.html;
}

Now the same site responds on both http://example.com and http://example.com:8080.

Open the port in the firewall

On a real server, changing the port is not enough on its own. If a firewall is running, it will block the new port until you allow it. nginx is listening, but the traffic never arrives.

sudo ufw allow 8080/tcp

If you skip this, the page simply times out from the outside even though nginx -t passed and the service is running. It is one of the most common "but it works locally" traps.

There is a matching gotcha in the other direction. Ports below 1024, including 80 itself, are privileged: only a process started with root privileges may bind them. High ports like 8080 are not privileged, so a quick test on 8080 can succeed while the same config on 80 fails to bind. If a low port refuses to open, check that nginx is being started the usual way (through its service) rather than by hand as a normal user.

This is not the same as a reverse proxy

Here is the distinction that trips everyone up.

• listen 8080 means nginx itself answers on port 8080. The port is part of the public URL.
• If instead you have an app running on a port (say a Node app on 3000) and you want visitors to reach it on plain port 80, you do not use listen 3000. You keep nginx on port 80 and forward requests to the app with proxy_pass, which is the reverse proxy chapter.

A quick way to remember it:

• listen PORT - the port nginx receives on (visible in the URL).
• proxy_pass http://127.0.0.1:PORT - the port of an internal app nginx forwards to (invisible to the visitor).

Wanting to "hide" an app that runs on 3000 by writing listen 3000 in nginx is the classic mix-up: that tells nginx to listen on 3000 instead of forwarding to the app there. They are opposite things.

Common mistake

Forgetting the port in the URL. After setting listen 8080, opening http://example.com (no port) hits port 80, where nothing is listening, so it fails. The site is fine - you just need http://example.com:8080. The second most common miss is the firewall: the port works on the server itself but not from another machine until you allow it.

FAQ

How do I run nginx on port 8080 instead of 80?

Set listen 8080; in the server block, run nginx -t, reload nginx, and open http://yourdomain:8080. On a server, also allow the port in the firewall with sudo ufw allow 8080/tcp.

Why do I have to put the port in the address?

Browsers only assume a port for the standard schemes: 80 for http:// and 443 for https://. Any other port is not assumed, so you must type it, like :8080.

Can nginx listen on two ports at the same time?

Yes. Add more than one listen line to the same server block, for example listen 80; and listen 8080;, and the block answers on both.

My app runs on port 3000 - should I use listen 3000?

No. Leave nginx on 80 (or 443) and forward to the app with proxy_pass http://127.0.0.1:3000;. listen sets the port nginx receives on; proxy_pass sets the app port it forwards to. See the reverse proxy chapter.