Socket hang up: server

client.js

var HttpsProxyAgent = require('https-proxy-agent');
require('isomorphic-fetch');

// Attempt to fetch the origin server, but proxied through the proxy server...works in browser, but not on the CLI
// with `node fetch.js`
fetch('http://localhost:8818', {
  agent: new HttpsProxyAgent('http://username:password@localhost:9818')
}).then((res) => {
  console.log('Fetch response', res);
}).catch((err) => {
  console.error('Fetch error', err);
});

failure.txt

$ DEBUG=* node fetch.js 
  https-proxy-agent creating new HttpsProxyAgent instance: Url { protocol: 'http:', slashes: true, auth: 'username:password', host: 'localhost:9818', port: '9818', hostname: 'localhost', hash: null, search: null, query: null, pathname: '/', path: '/', href: 'http://username:password@localhost:9818/' } +0ms
isomorphic-fetch: calling node-fetch
node-fetch: sending request
  https-proxy-agent onend +24ms
  https-proxy-agent onclose had error false +1ms
node-fetch: error { Error: socket hang up
    at createHangUpError (_http_client.js:322:15)
    at Socket.socketCloseListener (_http_client.js:363:25)
    at Socket.emit (events.js:187:15)
    at TCP._handle.close (net.js:606:12) code: 'ECONNRESET' }
Fetch error { FetchError: request to http://localhost:8818 failed, reason: socket hang up
    at ClientRequest.<anonymous> (/path/to/node_modules/node-fetch/index.js:136:11)
    at ClientRequest.emit (events.js:182:13)
    at Socket.socketCloseListener (_http_client.js:363:11)
    at Socket.emit (events.js:187:15)
    at TCP._handle.close (net.js:606:12)
  name: 'FetchError',
  message:
   'request to http://localhost:8818 failed, reason: socket hang up',
  type: 'system',
  errno: 'ECONNRESET',
  code: 'ECONNRESET' }

server.js

var http = require('http');
var httpProxy = require('http-proxy');

// Create origin server at localhost:8818
server = http.createServer(async (req, res) => {
  console.log('Server received', req.url);
  res.writeHead(200, { 'Content-Type': 'application/json' });
  res.write(JSON.stringify({ 'a': 'b' }));
  res.end();
});

server.on('error', (err) => {
  res.writeHead(500, {
    'Content-Type': 'text/plain'
  });

  res.end('Something went wrong.');
});

server.listen(8818, () => { console.log('Origin server is listening...'); });

// Create proxy server at localhost:9818 pointing to localhost:8818
proxy = httpProxy.createProxyServer({ target: 'http://localhost:8818'}).listen(9818, () => {
  console.log('Proxy server is listening...');
});

proxy.on('error', function (err, req, res) {
  res.writeHead(500, {
    'Content-Type': 'text/plain'
  });

  res.end('Something went wrong.');
});