Enum AioError 

pub enum AioError {
    TimedOut,
    Cancelled,
    Operation(NonZeroU32),
}

Errors that can occur during async I/O operations.

AioError represents the various failure conditions that can occur when performing asynchronous operations with NNG sockets.

Error categories

Transient errors

• AioError::TimedOut: Operation exceeded its timeout period. Only returned if a timeout is specifically set for the operation, which is not usually the case.
• AioError::Cancelled: Operation was cancelled (usually due to dropping the future). This error variant is usually not exposed to application code, and tends to only arise internally in the anng state machines.

Protocol/Network errors

• AioError::Operation: Underlying NNG operation failed (see error code for details).

Variants

TimedOut

Operation exceeded its timeout period.

This indicates the operation was started but did not complete within the configured timeout. The operation has been cancelled and can be safely retried.

Common Causes

• Network connectivity issues
• Remote endpoint overloaded or unresponsive
• Configured timeout too aggressive for network conditions

Cancelled

Operation was cancelled before completion.

This typically occurs when:

• The future was dropped before completion
• A timeout was applied externally (e.g., tokio::time::timeout)
• The application is shutting down

Cancelled operations are cleaned up properly and leave the socket in a consistent state.

Operation(NonZeroU32)

Underlying NNG operation failed with the given error code.

The error code corresponds to NNG’s error constants. Common codes include:

• NNG_ECONNREFUSED (61): Connection refused by remote endpoint
• NNG_ECONNRESET (54): Connection reset by peer
• NNG_EHOSTUNREACH (65): Host unreachable
• NNG_EADDRINUSE (48): Address already in use
• NNG_ESTATE (71): Protocol state violation

See the NNG documentation for a complete list of error codes. You can also get them from the nng_sys crate.

Trait Implementations

impl Clone for AioError

fn clone(&self) -> AioError

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for AioError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for AioError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Error for AioError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl From<AioError> for Error

fn from(err: AioError) -> Self

Converts to this type from the input type.

impl PartialEq for AioError

fn eq(&self, other: &AioError) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for AioError

impl StructuralPartialEq for AioError