Enum ProtocolError 

pub enum ProtocolError {
    UnmaskedFrame,
    MaskedFrame,
    InvalidOpcode(u8),
    InvalidLength(usize),
    BadOpCode,
    Overflow,
    ContinuationNotStarted,
    ContinuationStarted,
    ContinuationFragment(OpCode),
    SendClosed,
    RecvClosed,
    UnexpectedEof,
}

WebSocket protocol errors.

Close handshake errors

SendClosed, RecvClosed, and UnexpectedEof are related to the WebSocket close handshake. Their meaning depends on the context in which they are observed:

SendClosed

Returned by [ResponseSender::send] when a Close frame has already been sent on this session. This can happen in two scenarios:

• You called close() and then tried to send more messages. After sending a Close frame, no further messages are permitted per RFC 6455.
• A concurrent sender (via [ResponseWeakSender::upgrade]) already initiated the close. The caller observing this error should return gracefully — the shutdown is already in progress.

RecvClosed

Returned by [RequestStream] (as WsError::Protocol(ProtocolError::RecvClosed)) when the stream is polled after a Close frame has already been received and yielded. The caller should have stopped polling after observing Message::Close. Receiving this error means:

• The remote peer sent a Close frame, which was already yielded as Ok(Message::Close(_)).
• The caller should respond with a Close frame via [ResponseSender] (if not already sent) and then drop both the stream and sender.

UnexpectedEof

Returned by [RequestStream] when the underlying transport closed without a Close frame. This is an abnormal closure — the remote peer disconnected without following the WebSocket protocol. The associated connection should not be reused.

Typical close flows

Remote-initiated close:

1. [RequestStream] yields Ok(Message::Close(reason)).
2. Caller sends a Close frame back via [ResponseSender::close].
3. Caller drops both the stream and sender.

Local-initiated close:

1. Caller calls [ResponseSender::close].
2. Caller continues polling [RequestStream] for the peer’s Close echo.
3. [RequestStream] yields Ok(Message::Close(_)) — handshake complete.
4. Caller drops the stream. Any concurrent senders attempting to send will observe SendClosed.

Timeout on close echo:

1. Caller calls [ResponseSender::close].
2. Caller polls [RequestStream] with a timeout.
3. Timeout expires — caller sends an error via [ResponseSender::send_error] to signal the I/O layer to shut down the connection.

Variants

UnmaskedFrame

MaskedFrame

InvalidOpcode(u8)

InvalidLength(usize)

BadOpCode

Overflow

ContinuationNotStarted

ContinuationStarted

ContinuationFragment(OpCode)

SendClosed

A Close frame has already been sent. No further messages can be sent.

RecvClosed

A Close frame has already been received. The caller should stop polling the stream.

UnexpectedEof

The underlying transport closed without a Close frame. This is an abnormal closure.

Trait Implementations

impl Debug for ProtocolError

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

Formats the value using the given formatter.

impl Display for ProtocolError

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

Formats the value using the given formatter.

impl Error for ProtocolError

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<OpCode> for ProtocolError

fn from(e: OpCode) -> Self

Converts to this type from the input type.

impl<E> From<ProtocolError> for WsError<E>

fn from(e: ProtocolError) -> Self

Converts to this type from the input type.