How can I find out where a port number for a React website is saved?

I have a Debian machine, I can see that a React website is running on port 4173 but can't find out where it is so that I can change the port.

I assume it is in some config file somewhere.

• it's not in package.json

{
  "name": "debiantest",
  "private": true,
  "version": "0.0.0",
  "scripts": {
    "dev": "vite",
    "build": "vite build",
    "preview": "vite preview --host"
  },
  "dependencies": {
    "react": "^18.0.0",
    "react-dom": "^18.0.0"
  },
  "devDependencies": {
    "@types/react": "^18.0.0",
    "@types/react-dom": "^18.0.0",
    "@vitejs/plugin-react": "^1.3.0",
    "vite": "^2.9.5"
  }
}

• I don't find this port or site listed in /etc/nginx/sites-enabled/default

• with grep I found that the number is in node_modules/caniuse-lite/data/agents.js

"","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","tC","","",""],E:"KaiOS Browser",F:{tC:1527811200}}}; node_modules/vite/dist/node/chunks/dep-3397b401.js: const port = (_b = options.port) !== null && _b !== void 0 ? _b : 4173;

but am not sure where I would change it.

Where else can I look for this port number?

Stop the react server process, and then restart it using strace. It will be a little noisy, but you would want to look for "open" calls. This will show you all of the files the react server is opening as it runs. One of those files should contain the configuration data.

Here's an example using a stock Apache HTTPD server:

strace -f httpd 2>&1 | grep open

Will show you that the httpd process opens lots of files, and looking at those, you can find valuable information in these:

open("/etc/httpd/conf/httpd.conf", O_RDONLY|O_CLOEXEC) = 3
open("/etc/httpd/conf.d/ssl.conf", O_RDONLY|O_CLOEXEC) = 4
open("/etc/httpd/conf.d/perl.conf", O_RDONLY|O_CLOEXEC) = 4
open("/etc/httpd/conf.d/php.conf", O_RDONLY|O_CLOEXEC) = 4

It's just an example, the React server will have different files, but you should be able to filter through them (ie. grep -v) until you find something useful.