Passes requests (GET, POST and file upload/download) from server-1 to server-3 and back, passing through server-2.
server-2 uses http-proxy-middleware to proxy all the requests. That's all.
Install dependencies: npm i
Start servers: npm run 1, npm run 2, npm run 3
Web UI: http://localhost:5000/
CORS: https://expressjs.com/en/resources/middleware/cors.html
HTTP Proxy Middleware: https://www.npmjs.com/package/http-proxy-middleware
Body Parser: https://www.npmjs.com/package/body-parser
Multer: https://www.npmjs.com/package/multer
Download File: https://www.slingacademy.com/article/download-file-nodejs-express/