How to Resolve the 'Unrecognized SSL Message, Plaintext Connection' Exception in Java?

What causes the 'Unrecognized SSL message, plaintext connection' exception in Java, and how can I resolve it?

// No specific code snippet is applicable for this context.

The 'Unrecognized SSL message, plaintext connection' exception typically occurs when your Java application attempts to connect to an HTTPS server while using an improper protocol. This error indicates that the server is not set up to handle encrypted traffic on the port being accessed, or the connection is established without proper SSL/TLS negotiation.

// Example of establishing an HTTPS connection in Java:

import java.net.HttpURLConnection;
import java.net.URL;

public class HttpsConnectionExample {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://example.com"); // Ensure the URL starts with https
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setRequestMethod("GET");

        int responseCode = con.getResponseCode();
        System.out.println("Response Code : " + responseCode);
    }
}

Causes

• The server is not using SSL/TLS on the expected port.
• Using a wrong protocol (e.g., HTTP instead of HTTPS).
• Misconfigured server settings for HTTPS.

Solutions

• Ensure that you are using HTTPS when connecting to the server. Use the correct URL format, including 'https://' prefix.
• Verify that the server's port is configured to support SSL/TLS (default is 443 for HTTPS).
• Double-check server configurations to ensure SSL/TLS is enabled and properly set up.
• If applicable, check for firewall or proxy configurations that might be interfering with the connection.

Mistake: Forgetting to use 'https://' in the URL.

Solution: Always check that the URL for the connection is formatted with 'https://'.

Mistake: Attempting to connect to the wrong port, such as port 80 instead of port 443.

Solution: Ensure that the HTTPS connection is made on port 443, the default port for HTTPS.

Mistake: Assuming the server supports SSL/TLS without checking server configurations.

Solution: Verify that the server is correctly configured to support SSL/TLS connections.