Struct Connection

pub struct Connection(/* private fields */);

A QUIC connection.

If all references to a connection (including every clone of the Connection handle, streams of incoming streams, and the various stream types) have been dropped, then the connection will be automatically closed with an error_code of 0 and an empty reason. You can also close the connection explicitly by calling Connection::close().

Closing the connection immediately abandons efforts to deliver data to the peer. Upon receiving CONNECTION_CLOSE the peer may drop any stream data not yet delivered to the application. Connection::close() describes in more detail how to gracefully close a connection without losing application data.

May be cloned to obtain another handle to the same connection.

Implementations

impl Connection

pub fn weak_handle(&self) -> WeakConnectionHandle

Returns a weak reference to the inner connection struct.

pub fn open_uni(&self) -> OpenUni<'_>

Initiate a new outgoing unidirectional stream.

Streams are cheap and instantaneous to open unless blocked by flow control. As a consequence, the peer won’t be notified that a stream has been opened until the stream is actually used.

pub fn open_bi(&self) -> OpenBi<'_>

Initiate a new outgoing bidirectional stream.

Streams are cheap and instantaneous to open unless blocked by flow control. As a consequence, the peer won’t be notified that a stream has been opened until the stream is actually used. Calling open_bi() then waiting on the RecvStream without writing anything to SendStream will never succeed.

pub fn accept_uni(&self) -> AcceptUni<'_>

Accept the next incoming uni-directional stream

pub fn accept_bi(&self) -> AcceptBi<'_>

Accept the next incoming bidirectional stream

Important Note: The Connection that calls open_bi() must write to its SendStream before the other Connection is able to accept_bi(). Calling open_bi() then waiting on the RecvStream without writing anything to SendStream will never succeed.

pub fn read_datagram(&self) -> ReadDatagram<'_>

Receive an application datagram

pub async fn closed(&self) -> ConnectionError

Wait for the connection to be closed for any reason

Despite the return type’s name, closed connections are often not an error condition at the application layer. Cases that might be routine include ConnectionError::LocallyClosed and ConnectionError::ApplicationClosed.

pub fn close_reason(&self) -> Option<ConnectionError>

If the connection is closed, the reason why.

Returns None if the connection is still open.

pub fn close(&self, error_code: VarInt, reason: &[u8])

Close the connection immediately.

Pending operations will fail immediately with ConnectionError::LocallyClosed. No more data is sent to the peer and the peer may drop buffered data upon receiving the CONNECTION_CLOSE frame.

error_code and reason are not interpreted, and are provided directly to the peer.

reason will be truncated to fit in a single packet with overhead; to improve odds that it is preserved in full, it should be kept under 1KiB.

Gracefully closing a connection

Only the peer last receiving application data can be certain that all data is delivered. The only reliable action it can then take is to close the connection, potentially with a custom error code. The delivery of the final CONNECTION_CLOSE frame is very likely if both endpoints stay online long enough, and Endpoint::wait_idle() can be used to provide sufficient time. Otherwise, the remote peer will time out the connection, provided that the idle timeout is not disabled.

The sending side can not guarantee all stream data is delivered to the remote application. It only knows the data is delivered to the QUIC stack of the remote endpoint. Once the local side sends a CONNECTION_CLOSE frame in response to calling close() the remote endpoint may drop any data it received but is as yet undelivered to the application, including data that was acknowledged as received to the local endpoint.

pub fn send_datagram(&self, data: Bytes) -> Result<(), SendDatagramError>

Transmit data as an unreliable, unordered application datagram

Application datagrams are a low-level primitive. They may be lost or delivered out of order, and data must both fit inside a single QUIC packet and be smaller than the maximum dictated by the peer.

pub fn send_datagram_wait(&self, data: Bytes) -> SendDatagram<'_>

Transmit data as an unreliable, unordered application datagram

Unlike send_datagram(), this method will wait for buffer space during congestion conditions, which effectively prioritizes old datagrams over new datagrams.

See send_datagram() for details.

pub fn max_datagram_size(&self) -> Option<usize>

Compute the maximum size of datagrams that may be passed to send_datagram().

Returns None if datagrams are unsupported by the peer or disabled locally.

This may change over the lifetime of a connection according to variation in the path MTU estimate. The peer can also enforce an arbitrarily small fixed limit, but if the peer’s limit is large this is guaranteed to be a little over a kilobyte at minimum.

Not necessarily the maximum size of received datagrams.

pub fn datagram_send_buffer_space(&self) -> usize

Bytes available in the outgoing datagram buffer

When greater than zero, calling send_datagram() with a datagram of at most this size is guaranteed not to cause older datagrams to be dropped.

pub fn remote_address(&self) -> SocketAddr

The peer’s UDP address

If ServerConfig::migration is true, clients may change addresses at will, e.g. when switching to a cellular internet connection.

pub fn local_ip(&self) -> Option<IpAddr>

The local IP address which was used when the peer established the connection

This can be different from the address the endpoint is bound to, in case the endpoint is bound to a wildcard address like 0.0.0.0 or ::.

This will return None for clients, or when the platform does not expose this information. See quinn_udp::RecvMeta::dst_ip for a list of supported platforms when using quinn_udp for I/O, which is the default.

pub fn rtt(&self) -> Duration

Current best estimate of this connection’s latency (round-trip-time)

pub fn stats(&self) -> ConnectionStats

Returns connection statistics

pub fn congestion_state(&self) -> Box<dyn Controller>

Current state of the congestion control algorithm, for debugging purposes

pub fn handshake_data(&self) -> Option<Box<dyn Any>>

Parameters negotiated during the handshake

Guaranteed to return Some on fully established connections or after Connecting::handshake_data() succeeds. See that method’s documentations for details on the returned value.

pub fn peer_identity(&self) -> Option<Box<dyn Any>>

Cryptographic identity of the peer

The dynamic type returned is determined by the configured Session. For the default rustls session, the return value can be downcast to a Vec<rustls::pki_types::CertificateDer>

pub fn stable_id(&self) -> usize

A stable identifier for this connection

Peer addresses and connection IDs can change, but this value will remain fixed for the lifetime of the connection.

pub fn export_keying_material( &self, output: &mut [u8], label: &[u8], context: &[u8], ) -> Result<(), ExportKeyingMaterialError>

Derive keying material from this connection’s TLS session secrets.

When both peers call this method with the same label and context arguments and output buffers of equal length, they will get the same sequence of bytes in output. These bytes are cryptographically strong and pseudorandom, and are suitable for use as keying material.

See RFC5705 for more information.

pub fn set_max_concurrent_uni_streams(&self, count: VarInt)

Modify the number of remotely initiated unidirectional streams that may be concurrently open

No streams may be opened by the peer unless fewer than count are already open. Large counts increase both minimum and worst-case memory consumption.

pub fn set_receive_window(&self, receive_window: VarInt)

See proto::TransportConfig::receive_window()

pub fn set_max_concurrent_bi_streams(&self, count: VarInt)

Modify the number of remotely initiated bidirectional streams that may be concurrently open

No streams may be opened by the peer unless fewer than count are already open. Large counts increase both minimum and worst-case memory consumption.

pub fn observed_external_addr(&self) -> Receiver<Option<SocketAddr>>

Track changed on our external address as reported by the peer.

Trait Implementations

impl Clone for Connection

fn clone(&self) -> Connection

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Connection

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

Formats the value using the given formatter.