REST API Error: read ECONNRESET

I'm feeling like this is something happening on your local network or HTTP client config, not the server.

What's your endpoint (there's no harm in posting it here as long as you don't provide credentials).

I agree with @Sanford Whiteman‌ in that it's most likely a local problem. That error and come from anywhere along the connectivity path, but the cause is most likely local. It could be configuration problem with your HTTP client, a proxy server, proxy config, or even faulty equipment like a switch or router.

You should test making other connections using the same method. You could try retrieving the WSDL for Marketo's ancient SOAP API as a test: https://developers.marketo.com/soap-api/ You could also copy your API access token from the Launchpoint service in your Marketo Engage UI and use it to access /rest/v1/leads/describe2.json with a simple get request. Add the token as a query parameter like this: /rest/v1/leads/describe2.json?access_token=XY123 and test from a browser on the same machine which could rule out factors from your development environment. That should help narrow down the problem significantly.