Native Postman returns 503 when posting to localhost but Chrome Postman extension works

Question

I am trying to post simple Get commands to my service running on localhost using the Windows native Postman application (V4.8.0) but they fail. The Postman Console shows

Error: tunneling socket could not be established, statusCode=503

An example of the Get command is the following request for simple status message.

https://localhost/api/admin/status

The same commands work when directed to the identical service running on an external server. They also work posting to localhost directly from Chrome and when using the Chrome Postman extension (also V4.8.0).

SSL certificate verification is turned off.

Answer 1

I had the same problem. In my case env variables HTTP_PROXY, HTTPS_PROXY and NO_PROXY where set in my envirionment.

But in NO_PROXY the value for localhost was missing and that caused the 503 error. After adding localhost to NO_PROXY env variable, postman worked for my localhost adresses as well.