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Check TLS Certificate Expiry in Python: Handshake Errors for Expired, Wrong-Host and Self-Signed Certificates

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Self-Hosting & Infra intermediate 5 min read $0.01 Updated 2026-10-20

Executed against live hosts: a valid site returning TLSv1.3 with a future expiry, and badssl.com test hosts raising SSLCertVerificationError for expired, wrong-host and self-signed certificates, with the distinguishing message text.

Write a monitor that connects to a host, reads notAfter and the negotiated TLS version, and distinguishes expired, wrong-hostname and self-signed failures. Includes scheduling advice and renewal checks.

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#tls#ssl#monitoring#python#certificates

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