What does "empty reply from server" mean?

The "empty reply from server" error indicates that a zero length response was received - no HTTP headers or content, simply a closed TCP connection with no HTTP payload transmitted.

One common cause of this problem is attempting to make a plain HTTP request against the HTTPS (TLS / SSL) web server port. The HTTPS client will not be able to establish an encrypted session with the plain HTTP port, hence fails with the "empty reply from server" error.

The HTTP standard requires that when a client makes an HTTP request, the server must respond with a valid HTTP response code. Failure to do so violates the standard, and will trigger an "empty reply from server" error from our HTTP client, as well as other compliant HTTP clients.

Troubleshooting steps

1. Use the free HTTP test tool to verify if the problem persists. The test tool will provide diagnostic information showing the DNS resolution, TCP connection establishment, TLS / SSL encryption session creation and finally the HTTP request and response.
2. Use the free remote PING tool to verify that the server or cloud instance hosting the web server is reachable.