bogus EADDRINUSE on web socket opening (nodeJS on a droplet)

IT WORKS! Thanks so much for your fantastic support. The problem was, of course, mine: I had thought that nginx removed the “/be” as part of the forwarding. It doesn’t. So changing to, as you suggested, app.use(‘/be’, …)

did it. Now everything works, websockets or no.

many thanks again, this issue can be closed.

Heya,

Check if the port on your Droplet is indeed not being used by anything else.

You can do that by running

netstat -tulpen | grep 3002

Also make sure your Nginx is porperly configured to use that websocket.

You can paste your Nginx config to see if we can assist with that.

Hey 👋

The error you’re encountering (EADDRINUSE) typically indicates that the port you’re trying to use (3002 in this case) is already in use by another process.

Keep in mind that you can not have multiple services listening on the same port.

What you could do to verify if this is the case is:

1. Although you’ve already checked with lsof -i:3002 and found nothing, let’s double-check by also using the netstat command:

sudo netstat -tuln | grep 3002

That command should help confirm whether any process is indeed using port 3002. If nothing shows up, it suggests the port is not actively in use, but the issue might still persist due to other factors.

2. Sometimes, Node.js processes can linger, especially if you’ve been running and stopping the server multiple times. Use the following command to check if there are any rogue Node.js processes:

   ps aux | grep node
   

   If you see any Node.js processes running that shouldn’t be, you can kill them using:

   sudo kill -9 <PID>
   

   Replace <PID> with the actual process ID.

Then give it a try again after killing the process.

If this still does not work, can you share your Nginx config here so I could take a look?

Basically, if your WebSocket traffic should be handled by Nginx, you have to make sure that you’ve configured the Nginx server block correctly to proxy WebSocket connections to your Node.js app. Here’s an example of how you might configure Nginx for WebSocket proxying:

server {
    listen 80;
    server_name your_domain.com;

    location / {
        proxy_pass http://localhost:3001;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }

    location /websocket {
        proxy_pass http://localhost:3002;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

Also one more thing that you should check is that by default, new WebSocketServer({ port: 3002 }) will try to bind to all available IP addresses (both IPv4 and IPv6). If there is a conflict or an issue with binding to :: (all IPv6 addresses), you can try binding the WebSocket server specifically to 127.0.0.1 (localhost):

const wsS = new WebSocketServer({ host: '127.0.0.1', port: 3002, clientTracking: true });

Additionally, I would suggest checking the Node.js application logs and Nginx error logs (/var/log/nginx/error.log) for any additional clues.

Let me know how it goes!

- Bobby