Automatically use a different port if something is running on port 3000 already

[GrilloPress]

Not a hot burning issue but something that caught me out.

I have a few prototypes for different parts of the programme and across NHS Digital.

Occasionally I find myself running two prototypes that either connect together or I need to evaluate against each other.

Doing this I noticed that you can't run two versions of the prototype kit at once.

It appears initially that you can (one running on port :3000 and :3001 but actually you are only getting port :2000 being proxied.

Prototype one

Prototype two

The proxy URLs are the different, but the proxied port is not. You see two prototypes running but only one is. This is the same in the browser. 2000, 3000 and 3001 are all the same prototype.

I could change this in one prototype manually to not run on 2000 in app/config.js, but I was wondering how easy it would be to run a check on 2000 and if used, run on 2001?

[frankieroberto]

@GrilloPress sorry for the, err, 4 year delay - but thanks for reporting this!

I think we can add some code so that it’ll automatically switch to a different available port if needed.

Here’s the code that the GOVUK prototype kit uses for this: https://github.com/alphagov/govuk-prototype-kit/blob/main/lib/utils/index.js#L93-L130 - we should be able to copy that across to the NHS prototype kit.

[vickytnz]

As a note - if we do this it will be good to add documentation to the website about it to keep parity with the GOV.UK Prototype Kit website https://prototype-kit.service.gov.uk/docs/run-multiple-prototypes . Not going to start this until the feature is likely to go live but will be useful.