simple Forge 3-legged Oauth with node.js - autodesk-forge

Question

I am new to Forge and using node.js - I am having some difficulty getting a simple 3-legged Oauth process to work.
This is how far I have got below. It gives me the error "Cannot GET /api/forge/oauth/callback"
I have checked that my callback url matches what is in the Forge App.
Ultimately what I am trying to achieve is, getting the shared link for a newly created file in Fusion teams, or at least opening the browser to the file overview page.
Would anybody be able to help with this?
var express = require('express');
var ForgeSDK = require('forge-apis');
const { stringify } = require('node:querystring');
var opn = require('opn');
// Set up Express web server
var app = express();
// Set the Forge Variables
var FORGE_CLIENT_ID = 'client-id', FORGE_CLIENT_SECRET = 'client-secret', REDIRECT_URL = 'http://localhost:3000/api/forge/oauth/callback';
// This is for web server to start listening to port 3000
app.set('port', 3000);
var server = app.listen(app.get('port'), function () {
console.log('Server listening on port ' + server.address().port);
});
// Initialize the 3-legged OAuth2 client, set specific scopes and optionally set the `autoRefresh` parameter to true
// if you want the token to auto refresh
var autoRefresh = true;
var oAuth2ThreeLegged = new ForgeSDK.AuthClientThreeLegged(FORGE_CLIENT_ID, FORGE_CLIENT_SECRET, REDIRECT_URL, [
'data:read',
'data:write'
], autoRefresh);
// Generate a URL page that asks for permissions for the specified scopes.
var AuthURL = oAuth2ThreeLegged.generateAuthUrl();
console.log(AuthURL)
opn('https://developer.api.autodesk.com/authentication/v1/authorize?response_type=code&client_id=<<client-id>>&redirect_uri=http://localhost:3000/api/forge/oauth/callback&scope=data:read+data:write&state=undefined', {app: 'chrome'})

Answer 1

where is the callback API in your code?
BTW 3-Legged oauth is implemented here in nodejs, you can use it as reference:
https://learnforge.autodesk.io/#/oauth/3legged/nodejs