Initializing _start_connection_time with millis() in the header file is problematic. In C++, non-static member initializers are evaluated at object construction time, not at compile time. This means millis() will be called when the global WiFi object is constructed (before main() runs), which could be before the Arduino framework is initialized, potentially returning 0 or an undefined value.

The constructor in WiFi.cpp correctly initializes this to 0. Remove the = millis() initializer from the header and rely solely on the constructor initialization.

Potential integer overflow issue with timeout check. When _start_connection_time is 0 (as initialized in the constructor before begin() is called), this check will evaluate to true if less than _timeout milliseconds have passed since the device started (millis() < _timeout). This could cause isConnected() to incorrectly return WL_CONNECTING even when no connection attempt has been made.

Consider checking if _start_connection_time is non-zero before performing the timeout check, or resetting it to 0 when a connection succeeds or fails.

The condition if (clientConnected) on line 146 is redundant. At this point, we're already inside the if (clientConnected) block from line 132. This condition will always be true here. This redundant check should be removed, and the code inside should be dedented accordingly.

The method name isConnected() is ambiguous and potentially confusing. It suggests it returns a boolean (is/isn't connected), but it actually returns multiple connection states (WL_CONNECTED, WL_CONNECT_FAILED, WL_CONNECTING). This differs from the existing status() method only in that it also handles the timeout logic. Consider renaming to something more descriptive like getConnectionStatus() or checkConnectionState() to better reflect that it returns various states, not just a boolean.

The WL_CONNECT_FAILED state is not handled. If the WiFi connection fails (either immediately or after timeout), the code doesn't reset the status to WL_IDLE_STATUS to allow retry. Consider adding a check: if (status == WL_CONNECT_FAILED) { Serial.println("WiFi connection failed!"); status = WL_IDLE_STATUS; return; } before the WL_CONNECTED check.

The documentation says "Can be called to get the specified read timeout value" but doesn't document what this timeout is used for or how it differs from the general timeout. Consider adding more context like "Gets the timeout value used specifically for read operations during modem communication."

[nitpick] The serial baud rate has been changed from 115200 to 9600. This change appears unrelated to the non-blocking WiFi connection feature and slows down serial communication significantly. Unless there's a specific reason for this change, consider reverting to 115200 to maintain consistency with other examples and provide faster serial debugging.

The WL_CONNECT_FAILED state is not handled. If the WiFi connection fails (either immediately or after timeout), the code doesn't reset the status to WL_IDLE_STATUS to allow retry. Consider adding a check: if (status == WL_CONNECT_FAILED) { Serial.println("WiFi connection failed!"); status = WL_IDLE_STATUS; return; } before the WL_CONNECTED check.

When the server connection fails, the status is not reset. This means the code will stay in the WL_CONNECTED block and keep trying to connect to the server on every loop iteration. While the if (clientConnected) block won't execute, the loop will still continuously attempt to connect without the proper state management. Consider adding an else clause that handles the connection failure and potentially resets the status or adds a delay.

WiFiSSLClient connects to server over TLS without any server certificate validation or hostname verification. An on-path attacker (e.g., rogue AP on local network) can perform a MITM and intercept/modify traffic because the client does not verify the peer; fix by loading and enforcing a trusted CA or server certificate/fingerprint before client.connect, e.g., by calling the appropriate API to set a root CA or pinned certificate and validating the hostname.