Struct tokio::net::UnixStream

pub struct UnixStream { /* private fields */ }

A structure representing a connected Unix socket.

This socket can be connected directly with UnixStream::connect or accepted from a listener with UnixListener::accept. Additionally, a pair of anonymous Unix sockets can be created with UnixStream::pair.

To shut down the stream in the write direction, you can call the shutdown() method. This will cause the other peer to receive a read of length 0, indicating that no more data will be sent. This only closes the stream in one direction.

Implementations

impl UnixStream

pub async fn connect<P>(path: P) -> Result<UnixStream>

where P: AsRef<Path>,

Connects to the socket named by path.

This function will create a new Unix socket and connect to the path specified, associating the returned stream with the default event loop’s handle.

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

Waits for any of the requested ready states.

This function is usually paired with try_read() or try_write(). It can be used to concurrently read / write 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 read and write to the stream on the same task without splitting.

use tokio::io::Interest;
use tokio::net::UnixStream;
use std::error::Error;
use std::io;

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let dir = tempfile::tempdir().unwrap();
    let bind_path = dir.path().join("bind_path");
    let stream = UnixStream::connect(bind_path).await?;

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

        if ready.is_readable() {
            let mut data = vec![0; 1024];
            // Try to read data, this may still fail with `WouldBlock`
            // if the readiness event is a false positive.
            match stream.try_read(&mut data) {
                Ok(n) => {
                    println!("read {} bytes", n);        
                }
                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                    continue;
                }
                Err(e) => {
                    return Err(e.into());
                }
            }

        }

        if ready.is_writable() {
            // Try to write data, this may still fail with `WouldBlock`
            // if the readiness event is a false positive.
            match stream.try_write(b"hello world") {
                Ok(n) => {
                    println!("write {} bytes", n);
                }
                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                    continue;
                }
                Err(e) => {
                    return Err(e.into());
                }
            }
        }
    }
}

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_read().

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::UnixStream;
use std::error::Error;
use std::io;

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let bind_path = dir.path().join("bind_path");
    let stream = UnixStream::connect(bind_path).await?;

    let mut msg = vec![0; 1024];

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

        // Try to read data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match stream.try_read(&mut msg) {
            Ok(n) => {
                msg.truncate(n);
                break;
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e.into());
            }
        }
    }

    println!("GOT = {:?}", msg);
    Ok(())
}

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

Polls for read readiness.

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

Note that on multiple calls to poll_read_ready or poll_read, only the Waker from the Context passed to the most recent call is scheduled to receive a wakeup. (However, poll_write_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 unix stream is not ready for reading.
• Poll::Ready(Ok(())) if the unix stream 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 try_read(&self, buf: &mut [u8]) -> Result<usize>

Try to read data from the stream into the provided buffer, returning how many bytes were read.

Receives any pending data from the socket but does not wait for new data to arrive. On success, returns the number of bytes read. Because try_read() is non-blocking, the buffer does not have to be stored by the async task and can exist entirely on the stack.

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

Return

If data is successfully read, Ok(n) is returned, where n is the number of bytes read. If n is 0, then it can indicate one of two scenarios:

1. The stream’s read half is closed and will no longer yield data.
2. The specified buffer was 0 bytes in length.

If the stream is not ready to read data, Err(io::ErrorKind::WouldBlock) is returned.

Examples

use tokio::net::UnixStream;
use std::error::Error;
use std::io;

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let bind_path = dir.path().join("bind_path");
    let stream = UnixStream::connect(bind_path).await?;

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

        // Creating the buffer **after** the `await` prevents it from
        // being stored in the async task.
        let mut buf = [0; 4096];

        // Try to read data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match stream.try_read(&mut buf) {
            Ok(0) => break,
            Ok(n) => {
                println!("read {} bytes", n);
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e.into());
            }
        }
    }

    Ok(())
}

pub fn try_read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize>

Tries to read data from the stream into the provided buffers, returning how many bytes were read.

Data is copied to fill each buffer in order, with the final buffer written to possibly being only partially filled. This method behaves equivalently to a single call to try_read() with concatenated buffers.

Receives any pending data from the socket but does not wait for new data to arrive. On success, returns the number of bytes read. Because try_read_vectored() is non-blocking, the buffer does not have to be stored by the async task and can exist entirely on the stack.

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

Return

If data is successfully read, Ok(n) is returned, where n is the number of bytes read. Ok(0) indicates the stream’s read half is closed and will no longer yield data. If the stream is not ready to read data Err(io::ErrorKind::WouldBlock) is returned.

Examples

use tokio::net::UnixStream;
use std::error::Error;
use std::io::{self, IoSliceMut};

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let bind_path = dir.path().join("bind_path");
    let stream = UnixStream::connect(bind_path).await?;

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

        // Creating the buffer **after** the `await` prevents it from
        // being stored in the async task.
        let mut buf_a = [0; 512];
        let mut buf_b = [0; 1024];
        let mut bufs = [
            IoSliceMut::new(&mut buf_a),
            IoSliceMut::new(&mut buf_b),
        ];

        // Try to read data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match stream.try_read_vectored(&mut bufs) {
            Ok(0) => break,
            Ok(n) => {
                println!("read {} bytes", n);
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e.into());
            }
        }
    }

    Ok(())
}

pub fn try_read_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.

Receives any pending data from the socket but does not wait for new data to arrive. On success, returns the number of bytes read. Because try_read_buf() is non-blocking, the buffer does not have to be stored by the async task and can exist entirely on the stack.

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

Return

If data is successfully read, Ok(n) is returned, where n is the number of bytes read. Ok(0) indicates the stream’s read half is closed and will no longer yield data. If the stream is not ready to read data Err(io::ErrorKind::WouldBlock) is returned.

Examples

use tokio::net::UnixStream;
use std::error::Error;
use std::io;

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let bind_path = dir.path().join("bind_path");
    let stream = UnixStream::connect(bind_path).await?;

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

        let mut buf = Vec::with_capacity(4096);

        // Try to read data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match stream.try_read_buf(&mut buf) {
            Ok(0) => break,
            Ok(n) => {
                println!("read {} bytes", n);
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e.into());
            }
        }
    }

    Ok(())
}

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_write().

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::UnixStream;
use std::error::Error;
use std::io;

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let bind_path = dir.path().join("bind_path");
    let stream = UnixStream::connect(bind_path).await?;

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

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

    Ok(())
}

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

Polls for write readiness.

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

Note that on multiple calls to poll_write_ready or poll_write, only the Waker from the Context passed to the most recent call is scheduled to receive a wakeup. (However, poll_read_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 unix stream is not ready for writing.
• Poll::Ready(Ok(())) if the unix stream 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 fn try_write(&self, buf: &[u8]) -> Result<usize>

Tries to write a buffer to the stream, returning how many bytes were written.

The function will attempt to write the entire contents of buf, but only part of the buffer may be written.

This function is usually paired with writable().

Return

If data is successfully written, Ok(n) is returned, where n is the number of bytes written. If the stream is not ready to write data, Err(io::ErrorKind::WouldBlock) is returned.

Examples

use tokio::net::UnixStream;
use std::error::Error;
use std::io;

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let bind_path = dir.path().join("bind_path");
    let stream = UnixStream::connect(bind_path).await?;

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

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

    Ok(())
}

pub fn try_write_vectored(&self, buf: &[IoSlice<'_>]) -> Result<usize>

Tries to write several buffers to the stream, returning how many bytes were written.

Data is written from each buffer in order, with the final buffer read from possible being only partially consumed. This method behaves equivalently to a single call to try_write() with concatenated buffers.

This function is usually paired with writable().

Return

If data is successfully written, Ok(n) is returned, where n is the number of bytes written. If the stream is not ready to write data, Err(io::ErrorKind::WouldBlock) is returned.

Examples

use tokio::net::UnixStream;
use std::error::Error;
use std::io;

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    // Connect to a peer
    let dir = tempfile::tempdir().unwrap();
    let bind_path = dir.path().join("bind_path");
    let stream = UnixStream::connect(bind_path).await?;

    let bufs = [io::IoSlice::new(b"hello "), io::IoSlice::new(b"world")];

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

        // Try to write data, this may still fail with `WouldBlock`
        // if the readiness event is a false positive.
        match stream.try_write_vectored(&bufs) {
            Ok(n) => {
                break;
            }
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                continue;
            }
            Err(e) => {
                return Err(e.into());
            }
        }
    }

    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 UnixStream 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 UnixStream 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 from_std(stream: UnixStream) -> Result<UnixStream>

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

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

Notes

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

Examples

use tokio::net::UnixStream;
use std::os::unix::net::UnixStream as StdUnixStream;

let std_stream = StdUnixStream::connect("/path/to/the/socket")?;
std_stream.set_nonblocking(true)?;
let stream = UnixStream::from_std(std_stream)?;

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.

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

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

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

Examples

use std::error::Error;
use std::io::Read;
use tokio::net::UnixListener;

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let dir = tempfile::tempdir().unwrap();
    let bind_path = dir.path().join("bind_path");

    let mut data = [0u8; 12];
    let listener = UnixListener::bind(&bind_path)?;
    let (tokio_unix_stream, _) = listener.accept().await?;
    let mut std_unix_stream = tokio_unix_stream.into_std()?;
    std_unix_stream.set_nonblocking(false)?;
    std_unix_stream.read_exact(&mut data)?;
    Ok(())
}

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

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. Each socket will be associated with the default event loop’s handle.

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

Returns the socket address of the local half of this connection.

Examples

use tokio::net::UnixStream;

let dir = tempfile::tempdir().unwrap();
let bind_path = dir.path().join("bind_path");
let stream = UnixStream::connect(bind_path).await?;

println!("{:?}", stream.local_addr()?);

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

Returns the socket address of the remote half of this connection.

Examples

use tokio::net::UnixStream;

let dir = tempfile::tempdir().unwrap();
let bind_path = dir.path().join("bind_path");
let stream = UnixStream::connect(bind_path).await?;

println!("{:?}", stream.peer_addr()?);

pub fn peer_cred(&self) -> Result<UCred>

Returns effective credentials of the process which called connect or pair.

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

Returns the value of the SO_ERROR option.

pub fn split<'a>(&'a mut self) -> (ReadHalf<'a>, WriteHalf<'a>)

Splits a UnixStream into a read half and a write half, which can be used to read and write the stream concurrently.

This method is more efficient than into_split, but the halves cannot be moved into independently spawned tasks.

pub fn into_split(self) -> (OwnedReadHalf, OwnedWriteHalf)

Splits a UnixStream into a read half and a write half, which can be used to read and write the stream concurrently.

Unlike split, the owned halves can be moved to separate tasks, however this comes at the cost of a heap allocation.

Note: Dropping the write half will shut down the write half of the stream. This is equivalent to calling shutdown() on the UnixStream.

Trait Implementations

impl AsFd for UnixStream

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

Borrows the file descriptor.

impl AsRawFd for UnixStream

fn as_raw_fd(&self) -> RawFd

Extracts the raw file descriptor.

impl AsRef<UnixStream> for OwnedReadHalf

fn as_ref(&self) -> &UnixStream

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<UnixStream> for OwnedWriteHalf

fn as_ref(&self) -> &UnixStream

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<UnixStream> for ReadHalf<'_>

fn as_ref(&self) -> &UnixStream

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<UnixStream> for WriteHalf<'_>

fn as_ref(&self) -> &UnixStream

Converts this type into a shared reference of the (usually inferred) input type.

impl AsyncRead for UnixStream

fn poll_read( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut ReadBuf<'_>, ) -> Poll<Result<()>>

Attempts to read from the AsyncRead into buf.

impl AsyncWrite for UnixStream

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

Attempt to write bytes from buf into the object.

fn poll_write_vectored( self: Pin<&mut Self>, cx: &mut Context<'_>, bufs: &[IoSlice<'_>], ) -> Poll<Result<usize>>

Like poll_write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

Determines if this writer has an efficient poll_write_vectored implementation.

fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Result<()>>

Attempts to flush the object, ensuring that any buffered data reach their destination.

fn poll_shutdown(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Result<()>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down.

impl Debug for UnixStream

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

Formats the value using the given formatter.

impl TryFrom<UnixStream> for UnixStream

fn try_from(stream: UnixStream) -> Result<Self>

Consumes stream, returning the tokio I/O object.

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

type Error = Error

The type returned in the event of a conversion error.