ConnectionError

ConnectionError refers to failures encountered when attempting to establish or maintain a network connection. It is used as a generic label for errors in networking, client-server communication, or inter-process communication where a socket or channel cannot be opened or remains unusable.

In programming languages such as Python, ConnectionError is a built-in exception and a subclass of OSError. It serves as the base class for multiple more specific errors, including ConnectionAbortedError, ConnectionRefusedError, and ConnectionResetError. Some libraries define their own ConnectionError exceptions with different semantics; for example, the requests library exposes requests.exceptions.ConnectionError to signal failures during HTTP connections, often wrapping lower-level socket or timeout errors.

Common causes include DNS resolution failures, host unreachable, the target port not accepting connections, timeouts, network partitions, firewall rules, SSL/TLS handshake failures, and abrupt disconnects during data transfer. The exact meaning of the error can depend on the context and the library reporting it.

Handling considerations: distinguish between transient network issues and persistent problems; implement timeouts and retry policies; catch specific subtypes where possible; log relevant details (host, port, error message) to aid debugging; in library contexts, consider wrapping lower-level exceptions to preserve semantics.