Struct tokio::net::UnixDatagram

pub struct UnixDatagram { /* private fields */ }

An I/O object representing a Unix datagram socket.

A socket can be either named (associated with a filesystem path) or unnamed.

This type does not provide a split method, because this functionality can be achieved by wrapping the socket in an Arc. Note that you do not need a Mutex to share the UnixDatagram — an Arc<UnixDatagram> is enough. This is because all of the methods take &self instead of &mut self.

Note: named sockets are persisted even after the object is dropped and the program has exited, and cannot be reconnected. It is advised that you either check for and unlink the existing socket if it exists, or use a temporary file that is guaranteed to not already exist.

Examples

Using named sockets, associated with a filesystem path:

use tokio::net::UnixDatagram;
use tempfile::tempdir;

// We use a temporary directory so that the socket
// files left by the bound sockets will get cleaned up.
let tmp = tempdir()?;

// Bind each socket to a filesystem path
let tx_path = tmp.path().join("tx");
let tx = UnixDatagram::bind(&tx_path)?;
let rx_path = tmp.path().join("rx");
let rx = UnixDatagram::bind(&rx_path)?;

let bytes = b"hello world";
tx.send_to(bytes, &rx_path).await?;

let mut buf = vec![0u8; 24];
let (size, addr) = rx.recv_from(&mut buf).await?;

let dgram = &buf[..size];
assert_eq!(dgram, bytes);
assert_eq!(addr.as_pathname().unwrap(), &tx_path);

Using unnamed sockets, created as a pair

use tokio::net::UnixDatagram;

// Create the pair of sockets
let (sock1, sock2) = UnixDatagram::pair()?;

// Since the sockets are paired, the paired send/recv
// functions can be used
let bytes = b"hello world";
sock1.send(bytes).await?;

let mut buff = vec![0u8; 24];
let size = sock2.recv(&mut buff).await?;

let dgram = &buff[..size];
assert_eq!(dgram, bytes);

Implementations

impl UnixDatagram

pub async fn ready(&self, interest: Interest) -> Result<Ready>

Waits for any of the requested ready states.

This function is usually paired with try_recv() or try_send(). It can be used to concurrently recv / send to the same socket on a single task without splitting the socket.

The function may complete without the socket being ready. This is a false-positive and attempting an operation will return with io::ErrorKind::WouldBlock. The function can also return with an empty Ready set, so you should always check the returned value and possibly wait again if the requested states are not set.

Cancel safety

This method is cancel safe. Once a readiness event occurs, the method will continue to return immediately until the readiness event is consumed by an attempt to read or write that fails with WouldBlock or Poll::Pending.

Examples

Concurrently receive from and send to the socket on the same task without splitting.

use tokio::io::Interest;
use tokio::net::UnixDatagram;
use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let dir = tempfile::tempdir().unwrap();
    let client_path = dir.path().join("client.sock");
    let server_path = dir.path().join("server.sock");
    let socket = UnixDatagram::bind(&client_path)?;
    socket.connect(&server_path)?;

    loop {
        let ready = socket.ready(Interest::READABLE | Interest::WRITABLE).await?;

        if ready.is_readable() {
            let mut data = [0; 1024];
            match socket.try_recv(&mut data[..]) {
                Ok(n) => {
                    println!("received {:?}", &data[..n]);
                }
                // False-positive, continue
                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {}
                Err(e) => {
                    return Err(e);
                }
            }
        }

        if ready.is_writable() {
            // Write some data
            match socket.try_send(b"hello world") {
                Ok(n) => {
                    println!("sent {} bytes", n);
                }
                // False-positive, continue
                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {}
                Err(e) => {
                    return Err(e);
                }
            }
        }
    }
}

pub async fn writable(&self) -> Result<()>

Waits for the socket to become writable.

This function is equivalent to ready(Interest::WRITABLE) and is usually paired with try_send() or try_send_to().

The function may complete without the socket being writable. This is a false-positive and attempting a try_send() will return with io::ErrorKind::WouldBlock.

Cancel safety

This method is cancel safe. Once a readiness event occurs, the method will continue to return immediately until the readiness event is consumed by an attempt to write that fails with WouldBlock or Poll::Pending.

Examples

use tokio::net::UnixDatagram;
use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let dir = tempfile::tempdir().unwrap();
    let client_path = dir.path().join("client.sock");
    let server_path = dir.path().join("server.sock");
    let socket = UnixDatagram::bind(&client_path)?;
    socket.connect(&server_path)?;

    loop {
        // Wait for the socket to be writable
        socket.writable().await?;

        // Try to send data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match socket.try_send(b"hello world") {
            Ok(n) => {
                break;
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e);
            }
        }
    }

    Ok(())
}

pub fn poll_send_ready(&self, cx: &mut Context<'_>) -> Poll<Result<()>>

Polls for write/send readiness.

If the socket is not currently ready for sending, this method will store a clone of the Waker from the provided Context. When the socket becomes ready for sending, Waker::wake will be called on the waker.

Note that on multiple calls to poll_send_ready or poll_send, only the Waker from the Context passed to the most recent call is scheduled to receive a wakeup. (However, poll_recv_ready retains a second, independent waker.)

This function is intended for cases where creating and pinning a future via writable is not feasible. Where possible, using writable is preferred, as this supports polling from multiple tasks at once.

Return value

The function returns:

• Poll::Pending if the socket is not ready for writing.
• Poll::Ready(Ok(())) if the socket is ready for writing.
• Poll::Ready(Err(e)) if an error is encountered.

Errors

This function may encounter any standard I/O error except WouldBlock.

pub async fn readable(&self) -> Result<()>

Waits for the socket to become readable.

This function is equivalent to ready(Interest::READABLE) and is usually paired with try_recv().

The function may complete without the socket being readable. This is a false-positive and attempting a try_recv() will return with io::ErrorKind::WouldBlock.

Cancel safety

This method is cancel safe. Once a readiness event occurs, the method will continue to return immediately until the readiness event is consumed by an attempt to read that fails with WouldBlock or Poll::Pending.

Examples

use tokio::net::UnixDatagram;
use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let client_path = dir.path().join("client.sock");
    let server_path = dir.path().join("server.sock");
    let socket = UnixDatagram::bind(&client_path)?;
    socket.connect(&server_path)?;

    loop {
        // Wait for the socket to be readable
        socket.readable().await?;

        // The buffer is **not** included in the async task and will
        // only exist on the stack.
        let mut buf = [0; 1024];

        // Try to recv data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match socket.try_recv(&mut buf) {
            Ok(n) => {
                println!("GOT {:?}", &buf[..n]);
                break;
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e);
            }
        }
    }

    Ok(())
}

pub fn poll_recv_ready(&self, cx: &mut Context<'_>) -> Poll<Result<()>>

Polls for read/receive readiness.

If the socket is not currently ready for receiving, this method will store a clone of the Waker from the provided Context. When the socket becomes ready for reading, Waker::wake will be called on the waker.

Note that on multiple calls to poll_recv_ready, poll_recv or poll_peek, only the Waker from the Context passed to the most recent call is scheduled to receive a wakeup. (However, poll_send_ready retains a second, independent waker.)

This function is intended for cases where creating and pinning a future via readable is not feasible. Where possible, using readable is preferred, as this supports polling from multiple tasks at once.

Return value

The function returns:

• Poll::Pending if the socket is not ready for reading.
• Poll::Ready(Ok(())) if the socket is ready for reading.
• Poll::Ready(Err(e)) if an error is encountered.

Errors

This function may encounter any standard I/O error except WouldBlock.

pub fn bind<P>(path: P) -> Result<UnixDatagram>where
    P: AsRef<Path>,

Creates a new UnixDatagram bound to the specified path.

Examples

use tokio::net::UnixDatagram;
use tempfile::tempdir;

// We use a temporary directory so that the socket
// files left by the bound sockets will get cleaned up.
let tmp = tempdir()?;

// Bind the socket to a filesystem path
let socket_path = tmp.path().join("socket");
let socket = UnixDatagram::bind(&socket_path)?;

pub fn pair() -> Result<(UnixDatagram, UnixDatagram)>

Creates an unnamed pair of connected sockets.

This function will create a pair of interconnected Unix sockets for communicating back and forth between one another.

Examples

use tokio::net::UnixDatagram;

// Create the pair of sockets
let (sock1, sock2) = UnixDatagram::pair()?;

// Since the sockets are paired, the paired send/recv
// functions can be used
let bytes = b"hail eris";
sock1.send(bytes).await?;

let mut buff = vec![0u8; 24];
let size = sock2.recv(&mut buff).await?;

let dgram = &buff[..size];
assert_eq!(dgram, bytes);

pub fn from_std(datagram: UnixDatagram) -> Result<UnixDatagram>

Creates new UnixDatagram from a std::os::unix::net::UnixDatagram.

This function is intended to be used to wrap a UnixDatagram from the standard library in the Tokio equivalent.

Notes

The caller is responsible for ensuring that the socker is in non-blocking mode. Otherwise all I/O operations on the socket will block the thread, which will cause unexpected behavior. Non-blocking mode can be set using set_nonblocking.

Panics

This function panics if it is not called from within a runtime with IO enabled.

The runtime is usually set implicitly when this function is called from a future driven by a Tokio runtime, otherwise runtime can be set explicitly with Runtime::enter function.

Examples

use tokio::net::UnixDatagram;
use std::os::unix::net::UnixDatagram as StdUDS;
use tempfile::tempdir;

// We use a temporary directory so that the socket
// files left by the bound sockets will get cleaned up.
let tmp = tempdir()?;

// Bind the socket to a filesystem path
let socket_path = tmp.path().join("socket");
let std_socket = StdUDS::bind(&socket_path)?;
std_socket.set_nonblocking(true)?;
let tokio_socket = UnixDatagram::from_std(std_socket)?;

pub fn into_std(self) -> Result<UnixDatagram>

Turns a tokio::net::UnixDatagram into a std::os::unix::net::UnixDatagram.

The returned std::os::unix::net::UnixDatagram will have nonblocking mode set as true. Use set_nonblocking to change the blocking mode if needed.

Examples

let tokio_socket = tokio::net::UnixDatagram::bind("/path/to/the/socket")?;
let std_socket = tokio_socket.into_std()?;
std_socket.set_nonblocking(false)?;

pub fn unbound() -> Result<UnixDatagram>

Creates a new UnixDatagram which is not bound to any address.

Examples

use tokio::net::UnixDatagram;
use tempfile::tempdir;

// Create an unbound socket
let tx = UnixDatagram::unbound()?;

// Create another, bound socket
let tmp = tempdir()?;
let rx_path = tmp.path().join("rx");
let rx = UnixDatagram::bind(&rx_path)?;

// Send to the bound socket
let bytes = b"hello world";
tx.send_to(bytes, &rx_path).await?;

let mut buf = vec![0u8; 24];
let (size, addr) = rx.recv_from(&mut buf).await?;

let dgram = &buf[..size];
assert_eq!(dgram, bytes);

pub fn connect<P: AsRef<Path>>(&self, path: P) -> Result<()>

Connects the socket to the specified address.

The send method may be used to send data to the specified address. recv and recv_from will only receive data from that address.

Examples

use tokio::net::UnixDatagram;
use tempfile::tempdir;

// Create an unbound socket
let tx = UnixDatagram::unbound()?;

// Create another, bound socket
let tmp = tempdir()?;
let rx_path = tmp.path().join("rx");
let rx = UnixDatagram::bind(&rx_path)?;

// Connect to the bound socket
tx.connect(&rx_path)?;

// Send to the bound socket
let bytes = b"hello world";
tx.send(bytes).await?;

let mut buf = vec![0u8; 24];
let (size, addr) = rx.recv_from(&mut buf).await?;

let dgram = &buf[..size];
assert_eq!(dgram, bytes);

pub async fn send(&self, buf: &[u8]) -> Result<usize>

Sends data on the socket to the socket’s peer.

Cancel safety

This method is cancel safe. If send is used as the event in a tokio::select! statement and some other branch completes first, then it is guaranteed that the message was not sent.

Examples

use tokio::net::UnixDatagram;

// Create the pair of sockets
let (sock1, sock2) = UnixDatagram::pair()?;

// Since the sockets are paired, the paired send/recv
// functions can be used
let bytes = b"hello world";
sock1.send(bytes).await?;

let mut buff = vec![0u8; 24];
let size = sock2.recv(&mut buff).await?;

let dgram = &buff[..size];
assert_eq!(dgram, bytes);

pub fn try_send(&self, buf: &[u8]) -> Result<usize>

Tries to send a datagram to the peer without waiting.

Examples

use tokio::net::UnixDatagram;
use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let dir = tempfile::tempdir().unwrap();
    let client_path = dir.path().join("client.sock");
    let server_path = dir.path().join("server.sock");
    let socket = UnixDatagram::bind(&client_path)?;
    socket.connect(&server_path)?;

    loop {
        // Wait for the socket to be writable
        socket.writable().await?;

        // Try to send data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match socket.try_send(b"hello world") {
            Ok(n) => {
                break;
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e);
            }
        }
    }

    Ok(())
}

pub fn try_send_to<P>(&self, buf: &[u8], target: P) -> Result<usize>where
    P: AsRef<Path>,

Tries to send a datagram to the peer without waiting.

Examples

use tokio::net::UnixDatagram;
use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let dir = tempfile::tempdir().unwrap();
    let client_path = dir.path().join("client.sock");
    let server_path = dir.path().join("server.sock");
    let socket = UnixDatagram::bind(&client_path)?;

    loop {
        // Wait for the socket to be writable
        socket.writable().await?;

        // Try to send data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match socket.try_send_to(b"hello world", &server_path) {
            Ok(n) => {
                break;
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e);
            }
        }
    }

    Ok(())
}

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

Receives data from the socket.

Cancel safety

This method is cancel safe. If recv is used as the event in a tokio::select! statement and some other branch completes first, it is guaranteed that no messages were received on this socket.

Examples

use tokio::net::UnixDatagram;

// Create the pair of sockets
let (sock1, sock2) = UnixDatagram::pair()?;

// Since the sockets are paired, the paired send/recv
// functions can be used
let bytes = b"hello world";
sock1.send(bytes).await?;

let mut buff = vec![0u8; 24];
let size = sock2.recv(&mut buff).await?;

let dgram = &buff[..size];
assert_eq!(dgram, bytes);

pub fn try_recv(&self, buf: &mut [u8]) -> Result<usize>

Tries to receive a datagram from the peer without waiting.

Examples

use tokio::net::UnixDatagram;
use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let client_path = dir.path().join("client.sock");
    let server_path = dir.path().join("server.sock");
    let socket = UnixDatagram::bind(&client_path)?;
    socket.connect(&server_path)?;

    loop {
        // Wait for the socket to be readable
        socket.readable().await?;

        // The buffer is **not** included in the async task and will
        // only exist on the stack.
        let mut buf = [0; 1024];

        // Try to recv data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match socket.try_recv(&mut buf) {
            Ok(n) => {
                println!("GOT {:?}", &buf[..n]);
                break;
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e);
            }
        }
    }

    Ok(())
}

pub fn try_recv_buf_from<B: BufMut>(
    &self,
    buf: &mut B
) -> Result<(usize, SocketAddr)>

Tries to receive data from the socket without waiting.

This method can be used even if buf is uninitialized.

Examples

use tokio::net::UnixDatagram;
use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let client_path = dir.path().join("client.sock");
    let server_path = dir.path().join("server.sock");
    let socket = UnixDatagram::bind(&client_path)?;

    loop {
        // Wait for the socket to be readable
        socket.readable().await?;

        let mut buf = Vec::with_capacity(1024);

        // Try to recv data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match socket.try_recv_buf_from(&mut buf) {
            Ok((n, _addr)) => {
                println!("GOT {:?}", &buf[..n]);
                break;
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e);
            }
        }
    }

    Ok(())
}

pub async fn recv_buf_from<B: BufMut>(
    &self,
    buf: &mut B
) -> Result<(usize, SocketAddr)>

Receives from the socket, advances the buffer’s internal cursor and returns how many bytes were read and the origin.

This method can be used even if buf is uninitialized.

Examples

use tokio::net::UnixDatagram;
use tempfile::tempdir;

// We use a temporary directory so that the socket
// files left by the bound sockets will get cleaned up.
let tmp = tempdir()?;

// Bind each socket to a filesystem path
let tx_path = tmp.path().join("tx");
let tx = UnixDatagram::bind(&tx_path)?;
let rx_path = tmp.path().join("rx");
let rx = UnixDatagram::bind(&rx_path)?;

let bytes = b"hello world";
tx.send_to(bytes, &rx_path).await?;

let mut buf = Vec::with_capacity(24);
let (size, addr) = rx.recv_buf_from(&mut buf).await?;

let dgram = &buf[..size];
assert_eq!(dgram, bytes);
assert_eq!(addr.as_pathname().unwrap(), &tx_path);

pub fn try_recv_buf<B: BufMut>(&self, buf: &mut B) -> Result<usize>

Tries to read data from the stream into the provided buffer, advancing the buffer’s internal cursor, returning how many bytes were read.

This method can be used even if buf is uninitialized.

Examples

use tokio::net::UnixDatagram;
use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let client_path = dir.path().join("client.sock");
    let server_path = dir.path().join("server.sock");
    let socket = UnixDatagram::bind(&client_path)?;
    socket.connect(&server_path)?;

    loop {
        // Wait for the socket to be readable
        socket.readable().await?;

        let mut buf = Vec::with_capacity(1024);

        // Try to recv data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match socket.try_recv_buf(&mut buf) {
            Ok(n) => {
                println!("GOT {:?}", &buf[..n]);
                break;
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e);
            }
        }
    }

    Ok(())
}

pub async fn recv_buf<B: BufMut>(&self, buf: &mut B) -> Result<usize>

Receives data from the socket from the address to which it is connected, advancing the buffer’s internal cursor, returning how many bytes were read.

This method can be used even if buf is uninitialized.

Examples

use tokio::net::UnixDatagram;

// Create the pair of sockets
let (sock1, sock2) = UnixDatagram::pair()?;

// Since the sockets are paired, the paired send/recv
// functions can be used
let bytes = b"hello world";
sock1.send(bytes).await?;

let mut buff = Vec::with_capacity(24);
let size = sock2.recv_buf(&mut buff).await?;

let dgram = &buff[..size];
assert_eq!(dgram, bytes);

pub async fn send_to<P>(&self, buf: &[u8], target: P) -> Result<usize>where
    P: AsRef<Path>,

Sends data on the socket to the specified address.

Cancel safety

This method is cancel safe. If send_to is used as the event in a tokio::select! statement and some other branch completes first, then it is guaranteed that the message was not sent.

Examples

use tokio::net::UnixDatagram;
use tempfile::tempdir;

// We use a temporary directory so that the socket
// files left by the bound sockets will get cleaned up.
let tmp = tempdir()?;

// Bind each socket to a filesystem path
let tx_path = tmp.path().join("tx");
let tx = UnixDatagram::bind(&tx_path)?;
let rx_path = tmp.path().join("rx");
let rx = UnixDatagram::bind(&rx_path)?;

let bytes = b"hello world";
tx.send_to(bytes, &rx_path).await?;

let mut buf = vec![0u8; 24];
let (size, addr) = rx.recv_from(&mut buf).await?;

let dgram = &buf[..size];
assert_eq!(dgram, bytes);
assert_eq!(addr.as_pathname().unwrap(), &tx_path);

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

Receives data from the socket.

Cancel safety

This method is cancel safe. If recv_from is used as the event in a tokio::select! statement and some other branch completes first, it is guaranteed that no messages were received on this socket.

Examples

use tokio::net::UnixDatagram;
use tempfile::tempdir;

// We use a temporary directory so that the socket
// files left by the bound sockets will get cleaned up.
let tmp = tempdir()?;

// Bind each socket to a filesystem path
let tx_path = tmp.path().join("tx");
let tx = UnixDatagram::bind(&tx_path)?;
let rx_path = tmp.path().join("rx");
let rx = UnixDatagram::bind(&rx_path)?;

let bytes = b"hello world";
tx.send_to(bytes, &rx_path).await?;

let mut buf = vec![0u8; 24];
let (size, addr) = rx.recv_from(&mut buf).await?;

let dgram = &buf[..size];
assert_eq!(dgram, bytes);
assert_eq!(addr.as_pathname().unwrap(), &tx_path);

pub fn poll_recv_from(
    &self,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<SocketAddr>>

Attempts to receive a single datagram on the specified address.

Note that on multiple calls to a poll_* method in the recv direction, only the Waker from the Context passed to the most recent call will be scheduled to receive a wakeup.

Return value

The function returns:

• Poll::Pending if the socket is not ready to read
• Poll::Ready(Ok(addr)) reads data from addr into ReadBuf if the socket is ready
• Poll::Ready(Err(e)) if an error is encountered.

Errors

This function may encounter any standard I/O error except WouldBlock.

pub fn poll_send_to<P>(
    &self,
    cx: &mut Context<'_>,
    buf: &[u8],
    target: P
) -> Poll<Result<usize>>where
    P: AsRef<Path>,

Attempts to send data to the specified address.

Note that on multiple calls to a poll_* method in the send direction, only the Waker from the Context passed to the most recent call will be scheduled to receive a wakeup.

Return value

The function returns:

• Poll::Pending if the socket is not ready to write
• Poll::Ready(Ok(n)) n is the number of bytes sent.
• Poll::Ready(Err(e)) if an error is encountered.

Errors

This function may encounter any standard I/O error except WouldBlock.

pub fn poll_send(&self, cx: &mut Context<'_>, buf: &[u8]) -> Poll<Result<usize>>

Attempts to send data on the socket to the remote address to which it was previously connected.

The connect method will connect this socket to a remote address. This method will fail if the socket is not connected.

Note that on multiple calls to a poll_* method in the send direction, only the Waker from the Context passed to the most recent call will be scheduled to receive a wakeup.

Return value

The function returns:

• Poll::Pending if the socket is not available to write
• Poll::Ready(Ok(n)) n is the number of bytes sent
• Poll::Ready(Err(e)) if an error is encountered.

Errors

This function may encounter any standard I/O error except WouldBlock.

pub fn poll_recv(
    &self,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<()>>

Attempts to receive a single datagram message on the socket from the remote address to which it is connected.

The connect method will connect this socket to a remote address. This method resolves to an error if the socket is not connected.

Note that on multiple calls to a poll_* method in the recv direction, only the Waker from the Context passed to the most recent call will be scheduled to receive a wakeup.

Return value

The function returns:

• Poll::Pending if the socket is not ready to read
• Poll::Ready(Ok(())) reads data ReadBuf if the socket is ready
• Poll::Ready(Err(e)) if an error is encountered.

Errors

This function may encounter any standard I/O error except WouldBlock.

pub fn try_recv_from(&self, buf: &mut [u8]) -> Result<(usize, SocketAddr)>

Tries to receive data from the socket without waiting.

Examples

use tokio::net::UnixDatagram;
use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let client_path = dir.path().join("client.sock");
    let server_path = dir.path().join("server.sock");
    let socket = UnixDatagram::bind(&client_path)?;

    loop {
        // Wait for the socket to be readable
        socket.readable().await?;

        // The buffer is **not** included in the async task and will
        // only exist on the stack.
        let mut buf = [0; 1024];

        // Try to recv data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match socket.try_recv_from(&mut buf) {
            Ok((n, _addr)) => {
                println!("GOT {:?}", &buf[..n]);
                break;
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e);
            }
        }
    }

    Ok(())
}

pub fn try_io<R>(
    &self,
    interest: Interest,
    f: impl FnOnce() -> Result<R>
) -> Result<R>

Tries to read or write from the socket using a user-provided IO operation.

If the socket is ready, the provided closure is called. The closure should attempt to perform IO operation on the socket by manually calling the appropriate syscall. If the operation fails because the socket is not actually ready, then the closure should return a WouldBlock error and the readiness flag is cleared. The return value of the closure is then returned by try_io.

If the socket is not ready, then the closure is not called and a WouldBlock error is returned.

The closure should only return a WouldBlock error if it has performed an IO operation on the socket that failed due to the socket not being ready. Returning a WouldBlock error in any other situation will incorrectly clear the readiness flag, which can cause the socket to behave incorrectly.

The closure should not perform the IO operation using any of the methods defined on the Tokio UnixDatagram type, as this will mess with the readiness flag and can cause the socket to behave incorrectly.

This method is not intended to be used with combined interests. The closure should perform only one type of IO operation, so it should not require more than one ready state. This method may panic or sleep forever if it is called with a combined interest.

Usually, readable(), writable() or ready() is used with this function.

pub async fn async_io<R>(
    &self,
    interest: Interest,
    f: impl FnMut() -> Result<R>
) -> Result<R>

Reads or writes from the socket using a user-provided IO operation.

The readiness of the socket is awaited and when the socket is ready, the provided closure is called. The closure should attempt to perform IO operation on the socket by manually calling the appropriate syscall. If the operation fails because the socket is not actually ready, then the closure should return a WouldBlock error. In such case the readiness flag is cleared and the socket readiness is awaited again. This loop is repeated until the closure returns an Ok or an error other than WouldBlock.

The closure should only return a WouldBlock error if it has performed an IO operation on the socket that failed due to the socket not being ready. Returning a WouldBlock error in any other situation will incorrectly clear the readiness flag, which can cause the socket to behave incorrectly.

The closure should not perform the IO operation using any of the methods defined on the Tokio UnixDatagram type, as this will mess with the readiness flag and can cause the socket to behave incorrectly.

This method is not intended to be used with combined interests. The closure should perform only one type of IO operation, so it should not require more than one ready state. This method may panic or sleep forever if it is called with a combined interest.

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

Returns the local address that this socket is bound to.

Examples

For a socket bound to a local path

use tokio::net::UnixDatagram;
use tempfile::tempdir;

// We use a temporary directory so that the socket
// files left by the bound sockets will get cleaned up.
let tmp = tempdir()?;

// Bind socket to a filesystem path
let socket_path = tmp.path().join("socket");
let socket = UnixDatagram::bind(&socket_path)?;

assert_eq!(socket.local_addr()?.as_pathname().unwrap(), &socket_path);

For an unbound socket

use tokio::net::UnixDatagram;

// Create an unbound socket
let socket = UnixDatagram::unbound()?;

assert!(socket.local_addr()?.is_unnamed());

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

Returns the address of this socket’s peer.

The connect method will connect the socket to a peer.

Examples

For a peer with a local path

use tokio::net::UnixDatagram;
use tempfile::tempdir;

// Create an unbound socket
let tx = UnixDatagram::unbound()?;

// Create another, bound socket
let tmp = tempdir()?;
let rx_path = tmp.path().join("rx");
let rx = UnixDatagram::bind(&rx_path)?;

// Connect to the bound socket
tx.connect(&rx_path)?;

assert_eq!(tx.peer_addr()?.as_pathname().unwrap(), &rx_path);

For an unbound peer

use tokio::net::UnixDatagram;

// Create the pair of sockets
let (sock1, sock2) = UnixDatagram::pair()?;

assert!(sock1.peer_addr()?.is_unnamed());

pub fn take_error(&self) -> Result<Option<Error>>

Returns the value of the SO_ERROR option.

Examples

use tokio::net::UnixDatagram;

// Create an unbound socket
let socket = UnixDatagram::unbound()?;

if let Ok(Some(err)) = socket.take_error() {
    println!("Got error: {:?}", err);
}

pub fn shutdown(&self, how: Shutdown) -> Result<()>

Shuts down the read, write, or both halves of this connection.

This function will cause all pending and future I/O calls on the specified portions to immediately return with an appropriate value (see the documentation of Shutdown).

Examples

use tokio::net::UnixDatagram;
use std::net::Shutdown;

// Create an unbound socket
let (socket, other) = UnixDatagram::pair()?;

socket.shutdown(Shutdown::Both)?;

// NOTE: the following commented out code does NOT work as expected.
// Due to an underlying issue, the recv call will block indefinitely.
// See: https://github.com/tokio-rs/tokio/issues/1679
//let mut buff = vec![0u8; 24];
//let size = socket.recv(&mut buff).await?;
//assert_eq!(size, 0);

let send_result = socket.send(b"hello world").await;
assert!(send_result.is_err());

Trait Implementations

impl AsFd for UnixDatagram

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

Borrows the file descriptor.

impl AsRawFd for UnixDatagram

fn as_raw_fd(&self) -> RawFd

Extracts the raw file descriptor.

impl Debug for UnixDatagram

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

Formats the value using the given formatter.

impl TryFrom<UnixDatagram> for UnixDatagram

fn try_from(stream: UnixDatagram) -> Result<Self, Self::Error>

Consumes stream, returning the Tokio I/O object.

This is equivalent to UnixDatagram::from_std(stream).

type Error = Error

The type returned in the event of a conversion error.