Symptoms & Diagnosis
Python 3.13 introduces stricter defaults for SSL/TLS handshakes, which can trigger unexpected urllib3 protocol errors. Users frequently report “SSL: WRONG_VERSION_NUMBER” or “SSL: PROTOCOL_IS_NOT_SUPPORTED” when executing requests over unstable connections.
The issue often manifests during high-latency events, such as Python 3.13 WiFi drops. When the network signal fluctuates, the TLS handshake fails to complete, leading the urllib3 library to report a protocol violation instead of a simple timeout.
| Error Code | Typical Cause | Connection State |
|---|---|---|
| [SSL: WRONG_VERSION_NUMBER] | Server/Client mismatch or network interception. | Interrupted during handshake. |
| [SSL: PROTOCOL_IS_NOT_SUPPORTED] | Python 3.13 deprecation of TLS 1.0/1.1. | Attempting legacy connection. |
| SSLError: EOF occurred | Sudden WiFi drop or TCP reset. | Connection terminated prematurely. |
To diagnose, check your local OpenSSL version and verify if the target server supports TLS 1.2 or 1.3. Python 3.13 relies heavily on modern security standards that older hardware or misconfigured routers may struggle to maintain during signal drops.
Troubleshooting Guide
The first step is ensuring your environment uses the latest version of urllib3, as version 2.x includes critical fixes for Python 3.13 compatibility. Use the following command to upgrade your dependencies:
pip install --upgrade urllib3 requestsIf the error persists due to WiFi instability, you may need to implement a retry strategy with backoff. This prevents the “protocol error” from crashing your script when the network momentarily dips.
# Example of setting up a robust session
import urllib3
from urllib3.util import Retry
retries = Retry(total=5, backoff_factor=1, status_forcelist=[500, 502, 503, 504])
http = urllib3.PoolManager(retries=retries)For environments where the server uses legacy TLS versions, you must manually configure the SSLContext. Python 3.13 may block these by default to ensure security, but they can be re-enabled for internal legacy tools.
Prevention
Long-term prevention requires stabilizing the underlying network and enforcing strict TLS versions. Check your WiFi driver compatibility with Python’s socket implementation, as some modern power-saving features on laptop NICs cause micro-disconnects that trigger SSL protocol errors.
Enforce TLS 1.2+
Ensure your application explicitly requests modern protocols. This prevents the client from attempting to “downgrade” to vulnerable versions when a packet is dropped, which is a common trigger for the protocol error in Python 3.13.
Monitor Network Stability
Use OS-level tools to ensure your WiFi signal remains consistent. If you are developing on a system where WiFi drops are frequent, consider using a wired connection or a local proxy to handle the SSL lifting, isolating the Python process from network volatility.
Finally, keep your CA certificates updated. Outdated certificates can lead to handshake failures that Python 3.13 interprets as protocol errors. Run the following to update certificates on most systems:
pip install --upgrade certifi