Struct smol::net::UdpSocket

pub struct UdpSocket { /* private fields */ }

A UDP socket.

After creating a UdpSocket by binding it to a socket address, data can be sent to and received from any other socket address.

Cloning a UdpSocket creates another handle to the same socket. The socket will be closed when all handles to it are dropped.

Although UDP is a connectionless protocol, this implementation provides an interface to set an address where data should be sent and received from. After setting a remote address with connect(), data can be sent to and received from that address with send() and recv().

As stated in the User Datagram Protocol’s specification in IETF RFC 768, UDP is an unordered, unreliable protocol. Refer to TcpListener and TcpStream for TCP primitives.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:8080").await?;
let mut buf = vec![0u8; 20];

loop {
    // Receive a single datagram message.
    // If `buf` is too small to hold the entire message, it will be cut off.
    let (n, addr) = socket.recv_from(&mut buf).await?;

    // Send the message back to the same address that has sent it.
    socket.send_to(&buf[..n], &addr).await?;
}

Implementations

impl UdpSocket

pub async fn bind<A>(addr: A) -> impl Future<Output = Result<UdpSocket, Error>>where
    A: AsyncToSocketAddrs,

Creates a new UdpSocket bound to the given address.

Binding with a port number of 0 will request that the operating system assigns an available port to this socket. The assigned port can be queried via the local_addr() method.

If addr yields multiple addresses, binding will be attempted with each of the addresses until one succeeds and returns the socket. If none of the addresses succeed in creating a socket, the error from the last attempt is returned.

Examples

Create a UDP socket bound to 127.0.0.1:3400:

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:3400").await?;

Create a UDP socket bound to 127.0.0.1:3400. If that address is unavailable, then try binding to 127.0.0.1:3401:

use async_net::{SocketAddr, UdpSocket};

let addrs = [
    SocketAddr::from(([127, 0, 0, 1], 3400)),
    SocketAddr::from(([127, 0, 0, 1], 3401)),
];
let socket = UdpSocket::bind(&addrs[..]).await?;

pub fn local_addr(&self) -> Result<SocketAddr, Error>

Returns the local address this socket is bound to.

This can be useful, for example, when binding to port 0 to figure out which port was actually bound.

Examples

Bind to port 0 and then see which port was assigned by the operating system:

use async_net::{SocketAddr, UdpSocket};

let socket = UdpSocket::bind("127.0.0.1:0").await?;
println!("Bound to {}", socket.local_addr()?);

pub fn peer_addr(&self) -> Result<SocketAddr, Error>

Returns the remote address this socket is connected to.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
socket.connect("192.168.0.1:41203").await?;
println!("Connected to {}", socket.peer_addr()?);

pub async fn connect<A>(
    &self,
    addr: A
) -> impl Future<Output = Result<(), Error>>where
    A: AsyncToSocketAddrs,

Connects the UDP socket to an address.

When connected, methods send() and recv() will use the specified address for sending and receiving messages. Additionally, a filter will be applied to recv_from() so that it only receives messages from that same address.

If addr yields multiple addresses, connecting will be attempted with each of the addresses until the operating system accepts one. If none of the addresses are accepted, the error from the last attempt is returned.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:3400").await?;
socket.connect("127.0.0.1:8080").await?;

pub async fn recv_from(
    &self,
    buf: &mut [u8]
) -> impl Future<Output = Result<(usize, SocketAddr), Error>>

Receives a single datagram message.

On success, returns the number of bytes received and the address message came from.

This method must be called with a valid byte buffer of sufficient size to hold a message. If the received message is too long to fit into the buffer, it may be truncated.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;

let mut buf = vec![0u8; 1024];
let (n, addr) = socket.recv_from(&mut buf).await?;
println!("Received {} bytes from {}", n, addr);

pub async fn peek_from(
    &self,
    buf: &mut [u8]
) -> impl Future<Output = Result<(usize, SocketAddr), Error>>

Receives a single datagram message without removing it from the queue.

On success, returns the number of bytes peeked and the address message came from.

This method must be called with a valid byte buffer of sufficient size to hold a message. If the received message is too long to fit into the buffer, it may be truncated.

Successive calls return the same message. This is accomplished by passing MSG_PEEK as a flag to the underlying recvfrom system call.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;

let mut buf = vec![0u8; 1024];
let (n, addr) = socket.peek_from(&mut buf).await?;
println!("Peeked {} bytes from {}", n, addr);

pub async fn send_to<A>(
    &self,
    buf: &[u8],
    addr: A
) -> impl Future<Output = Result<usize, Error>>where
    A: AsyncToSocketAddrs,

Sends data to the given address.

On success, returns the number of bytes sent.

If addr yields multiple addresses, the message will only be sent to the first address.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
socket.send_to(b"hello", "127.0.0.1:4242").await?;

pub async fn recv(
    &self,
    buf: &mut [u8]
) -> impl Future<Output = Result<usize, Error>>

Receives a single datagram message from the connected address.

On success, returns the number of bytes received.

This method must be called with a valid byte buffer of sufficient size to hold a message. If the received message is too long to fit into the buffer, it may be truncated.

The connect() method connects this socket to an address. This method will fail if the socket is not connected.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
socket.connect("127.0.0.1:8080").await?;

let mut buf = vec![0u8; 1024];
let n = socket.recv(&mut buf).await?;
println!("Received {} bytes", n);

pub async fn peek(
    &self,
    buf: &mut [u8]
) -> impl Future<Output = Result<usize, Error>>

Receives a single datagram from the connected address without removing it from the queue.

On success, returns the number of bytes peeked.

This method must be called with a valid byte buffer of sufficient size to hold a message. If the received message is too long to fit into the buffer, it may be truncated.

Successive calls return the same message. This is accomplished by passing MSG_PEEK as a flag to the underlying recv system call.

The connect() method connects this socket to an address. This method will fail if the socket is not connected.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
socket.connect("127.0.0.1:8080").await?;

let mut buf = vec![0u8; 1024];
let n = socket.peek(&mut buf).await?;
println!("Peeked {} bytes", n);

pub async fn send(
    &self,
    buf: &[u8]
) -> impl Future<Output = Result<usize, Error>>

Sends data to the connected address.

The connect() method connects this socket to an address. This method will fail if the socket is not connected.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
socket.connect("127.0.0.1:8080").await?;
socket.send(b"hello").await?;

pub fn broadcast(&self) -> Result<bool, Error>

Gets the value of the SO_BROADCAST option for this socket.

If set to true, this socket is allowed to send packets to a broadcast address.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
println!("SO_BROADCAST is set to {}", socket.broadcast()?);

pub fn set_broadcast(&self, broadcast: bool) -> Result<(), Error>

Sets the value of the SO_BROADCAST option for this socket.

If set to true, this socket is allowed to send packets to a broadcast address.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
socket.set_broadcast(true)?;

pub fn multicast_loop_v4(&self) -> Result<bool, Error>

Gets the value of the IP_MULTICAST_LOOP option for this socket.

If set to true, multicast packets will be looped back to the local socket.

Note that this option may not have any affect on IPv6 sockets.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
println!("IP_MULTICAST_LOOP is set to {}", socket.multicast_loop_v4()?);

pub fn set_multicast_loop_v4(&self, multicast_loop_v4: bool) -> Result<(), Error>

Sets the value of the IP_MULTICAST_LOOP option for this socket.

If set to true, multicast packets will be looped back to the local socket.

Note that this option may not have any affect on IPv6 sockets.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
socket.set_multicast_loop_v4(true)?;

pub fn multicast_ttl_v4(&self) -> Result<u32, Error>

Gets the value of the IP_MULTICAST_TTL option for this socket.

Indicates the time-to-live value of outgoing multicast packets for this socket. The default value is 1, which means that multicast packets don’t leave the local network unless explicitly requested.

Note that this option may not have any effect on IPv6 sockets.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
println!("IP_MULTICAST_TTL is set to {}", socket.multicast_loop_v4()?);

pub fn set_multicast_ttl_v4(&self, ttl: u32) -> Result<(), Error>

Sets the value of the IP_MULTICAST_TTL option for this socket.

Indicates the time-to-live value of outgoing multicast packets for this socket. The default value is 1, which means that multicast packets don’t leave the local network unless explicitly requested.

Note that this option may not have any effect on IPv6 sockets.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
socket.set_multicast_ttl_v4(10)?;

pub fn multicast_loop_v6(&self) -> Result<bool, Error>

Gets the value of the IPV6_MULTICAST_LOOP option for this socket.

Controls whether this socket sees the multicast packets it sends itself.

Note that this option may not have any effect on IPv4 sockets.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
println!("IPV6_MULTICAST_LOOP is set to {}", socket.multicast_loop_v6()?);

pub fn set_multicast_loop_v6(&self, multicast_loop_v6: bool) -> Result<(), Error>

Sets the value of the IPV6_MULTICAST_LOOP option for this socket.

Controls whether this socket sees the multicast packets it sends itself.

Note that this option may not have any effect on IPv4 sockets.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
socket.set_multicast_loop_v6(true)?;

pub fn ttl(&self) -> Result<u32, Error>

Gets the value of the IP_TTL option for this socket.

This option configures the time-to-live field that is used in every packet sent from this socket.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
println!("IP_TTL is set to {}", socket.ttl()?);

pub fn set_ttl(&self, ttl: u32) -> Result<(), Error>

Sets the value of the IP_TTL option for this socket.

This option configures the time-to-live field that is used in every packet sent from this socket.

Examples

use async_net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:34254").await?;
socket.set_ttl(100)?;

pub fn join_multicast_v4(
    &self,
    multiaddr: Ipv4Addr,
    interface: Ipv4Addr
) -> Result<(), Error>

Executes an operation of the IP_ADD_MEMBERSHIP type.

This method specifies a new multicast group for this socket to join. Argument multiaddr must be a valid multicast address, and interface is the address of the local interface with which the system should join the multicast group. If it’s equal to INADDR_ANY then an appropriate interface is chosen by the system.

pub fn leave_multicast_v4(
    &self,
    multiaddr: Ipv4Addr,
    interface: Ipv4Addr
) -> Result<(), Error>

Executes an operation of the IP_DROP_MEMBERSHIP type.

This method leaves a multicast group. Argument multiaddr must be a valid multicast address, and interface is the index of the interface to leave.

pub fn join_multicast_v6(
    &self,
    multiaddr: &Ipv6Addr,
    interface: u32
) -> Result<(), Error>

Executes an operation of the IPV6_ADD_MEMBERSHIP type.

This method specifies a new multicast group for this socket to join. Argument multiaddr must be a valid multicast address, and interface is the index of the interface to join (or 0 to indicate any interface).

pub fn leave_multicast_v6(
    &self,
    multiaddr: &Ipv6Addr,
    interface: u32
) -> Result<(), Error>

Executes an operation of the IPV6_DROP_MEMBERSHIP type.

This method leaves a multicast group. Argument multiaddr must be a valid multicast address, and interface is the index of the interface to leave.

Trait Implementations

impl AsFd for UdpSocket

fn as_fd(&self) -> BorrowedFd<'_>

Borrows the file descriptor.

impl AsRawFd for UdpSocket

fn as_raw_fd(&self) -> i32

Extracts the raw file descriptor.

impl Clone for UdpSocket

fn clone(&self) -> UdpSocket

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for UdpSocket

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

Formats the value using the given formatter.

impl From<Async<UdpSocket>> for UdpSocket

fn from(socket: Async<UdpSocket>) -> UdpSocket

Converts to this type from the input type.

impl TryFrom<OwnedFd> for UdpSocket

type Error = Error

The type returned in the event of a conversion error.

fn try_from(
    value: OwnedFd
) -> Result<UdpSocket, <UdpSocket as TryFrom<OwnedFd>>::Error>

Performs the conversion.

impl TryFrom<UdpSocket> for UdpSocket

type Error = Error

The type returned in the event of a conversion error.

fn try_from(socket: UdpSocket) -> Result<UdpSocket, Error>

Performs the conversion.