I use HTTP sensors to monitor various external webpages. Some of these sensors fail to successfully check their target websites. For example, I get the following HTTP sensor errors depending on the monitored webpage and when SNI is used for SSL handling:
- Application protocol errors: 403 Forbidden, 400 Bad Request
- SSL/TLS protocol errors: Failed to establish secure connection, Error connecting with SSL, SSL handshake failure
What can be the reason for these protocol errors? Why do I get SSL handshake failures?