proxy.js

const sites = {
    "foo.localhost": 8001,
    "bar.localhost": 8003,
    "qux.localhost": 8004,
    "sam.localhost": 8005,
};

// new version based on:
// https://stackoverflow.com/questions/20351637/how-to-create-a-simple-http-proxy-in-node-js

const http = require('http');

const server = http.createServer((client_req, client_res) => {
    console.log('serve:', client_req.method, client_req.headers.host, client_req.url);
    console.log('serve:', "localhost", sites[client_req.headers.host], client_req.url);
    console.log();

    const options = {
        hostname: '127.0.0.1',
        port: sites[client_req.headers.host] ?? 9000,
        path: client_req.url,
        method: client_req.method,
        headers: client_req.headers
    };

    const proxy = http.request(options, function (res) {
        client_res.writeHead(res.statusCode, res.headers)
        res.pipe(client_res, {
            end: true
        });
    });

    client_req.pipe(proxy, {
        end: true
    });

});

server.listen(80);