sveltekit build port is always 3000 but it is not available in my server. How do you change port in svelte.config.js? - sveltekit

Question

Port 3000 is occupied in my hosting server. Now I'm building a sveltekit app.
When I use
npm run dev --port 4000
or npm run build and then
npm run preview --port 4000
I'm able to start the sveltekit using localhost:4000
My npm run build is always pointing me to
skapp#0.0.1 preview
> svelte-kit preview
SvelteKit v1.0.0-next.260
network: not exposed
local: http://localhost:3000
after searching online some of the possible solutions available online is to change the port in the adapter-node config env like so:
const config = {
kit: {
adapter: adapter({
out : 'buildit',
env : {
port : 4000,
}
// vite : {
// server : {strictPort : false}
// }
}),
}
};
export default config;
I go back and build the sveltekit again then run the command npm run preview again, like so:
npm run build
npm run preview
but the it gives me the same 3000 port. Some of the discussion online pointed to the vite flag where you set the strictPort to false and it will look for the next available port but that didn't change the port and the build still fixated on port 3000.
When I use npm run build --port 4000, while another app is running on port 3000, I get an error.
Error: listen EADDRINUSE: address already in use 127.0.0.1:3000
at Server.setupListenHandle [as _listen2] (net.js:1318:16)
at listenInCluster (net.js:1366:12)
at GetAddrInfoReqWrap.doListen [as callback] (net.js:1503:7)
at GetAddrInfoReqWrap.onlookup [as oncomplete] (dns.js:69:8)
Emitted 'error' event on Server instance at:
at emitErrorNT (net.js:1345:8)
at processTicksAndRejections (internal/process/task_queues.js:82:21) {
code: 'EADDRINUSE',
errno: -4091,
syscall: 'listen',
address: '127.0.0.1',
port: 3000
}
It seems like it is a server instance error. How to fix it?
It seems like fewer developers are interested in sveltekit because when I used to post a question about sapper, I used to get an answer within hours but I'm noticing that questions about sveltekit getting answered in days. Hopefully there are some developers out there keeping their eyes on sveltekit tag in stackoverflow.
So my question how to change the npm run build so the sveltekit app start using a different port. I'm not asking about npm run dev or npm run preview. My inquiry is about sveltekit to run on port 4000. How the npm run build could be used to build sveltekit app with a different port?

Answer 1

svelte-kit dev and svelte-kit preview are used for development and debugging purposes and should not be run for production builds.
when deploying to a server you run svelte-kit build to generate the final site (in your case that should be located in ./buildit)
i don't think that you can statically specify the port being used, but you can provide it when launching the server using an environment variable.
(i am using #sveltejs/adapter-node, so this might be different for other adapters)
PORT=1234 node buildit/index.js
i hope this is what you were asking for, to be honest i don't think i quite understood the question

Answer 2

change the port mentioned at the bottom on the index.js that was created in build folder...

Answer 3

After "npm run build", you can change the default port 3000 in the build\index.js file(Line 218).
const port = env('PORT', !path && '3000');
->
const port = env('PORT', !path && '1234');