# [−] [src] Struct tokio::net::TcpStream

    pub struct TcpStream { /* fields omitted */ }

A TCP stream between a local and a remote socket.

A TCP stream can either be created by connecting to an endpoint, via the `connect` method, or by accepting a connection from a listener.

Reading and writing to a `TcpStream` is usually done using the convenience methods found on the `AsyncReadExt` and `AsyncWriteExt` traits.

# Examples

    use tokio::net::TcpStream;
    use tokio::io::AsyncWriteExt;
    use std::error::Error;

    #[tokio::main]
    async fn main() -> Result<(), Box<dyn Error>> {
        // Connect to a peer
        let mut stream = TcpStream::connect("127.0.0.1:8080").await?;

        // Write some data.
        stream.write_all(b"hello world!").await?;

        Ok(())
    }

The `write_all` method is defined on the `AsyncWriteExt` trait.

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 TcpStream` [src]

#### `pub async fn connect<A: ToSocketAddrs>(addr: A) -> Result<TcpStream>` [src]

Opens a TCP connection to a remote host.

`addr` is an address of the remote host. Anything which implements the `ToSocketAddrs` trait can be supplied as the address. Note that strings only implement this trait when the `net` feature is enabled, as strings may contain domain names that need to be resolved.

If `addr` yields multiple addresses, connect will be attempted with each of the addresses until a connection is successful. If none of the addresses result in a successful connection, the error returned from the last connection attempt (the last address) is returned.

# Examples

    use tokio::net::TcpStream;
    use tokio::io::AsyncWriteExt;
    use std::error::Error;

    #[tokio::main]
    async fn main() -> Result<(), Box<dyn Error>> {
        // Connect to a peer
        let mut stream = TcpStream::connect("127.0.0.1:8080").await?;

        // Write some data.
        stream.write_all(b"hello world!").await?;

        Ok(())
    }

The `write_all` method is defined on the `AsyncWriteExt` trait.

#### `pub fn from_std(stream: TcpStream) -> Result<TcpStream>` [src]

Creates new `TcpStream` from a `std::net::TcpStream`.

This function is intended to be used to wrap a TCP stream from the standard library in the Tokio equivalent. The conversion assumes nothing about the underlying stream; it is left up to the user to set it in non-blocking mode.

# Examples

    use std::error::Error;
    use tokio::net::TcpStream;

    #[tokio::main]
    async fn main() -> Result<(), Box<dyn Error>> {
        let std_stream = std::net::TcpStream::connect("127.0.0.1:34254")?;
        std_stream.set_nonblocking(true)?;
        let stream = TcpStream::from_std(std_stream)?;
        Ok(())
    }

# Panics

This function panics if thread-local runtime is not set.

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<TcpStream>` [src]

Turn a `tokio::net::TcpStream` into a `std::net::TcpStream`.

The returned `std::net::TcpStream` 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::TcpListener;

    #[tokio::main]
    async fn main() -> Result<(), Box<dyn Error>> {
        let mut data = [0u8; 12];
        let listener = TcpListener::bind("127.0.0.1:34254").await?;
        let (tokio_tcp_stream, _) = listener.accept().await?;
        let mut std_tcp_stream = tokio_tcp_stream.into_std()?;
        std_tcp_stream.set_nonblocking(false)?;
        std_tcp_stream.read_exact(&mut data)?;
        Ok(())
    }

#### `pub fn local_addr(&self) -> Result<SocketAddr>` [src]

Returns the local address that this stream is bound to.

# Examples

    use tokio::net::TcpStream;

    let stream = TcpStream::connect("127.0.0.1:8080").await?;

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

#### `pub fn peer_addr(&self) -> Result<SocketAddr>` [src]

Returns the remote address that this stream is connected to.

# Examples

    use tokio::net::TcpStream;

    let stream = TcpStream::connect("127.0.0.1:8080").await?;

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

#### `pub fn poll_peek(
&self,
cx: &mut Context<'_>,
buf: &mut ReadBuf<'_>
) -> Poll<Result<usize>>` [src]

Attempts to receive data on the socket, without removing that data from the queue, registering the current task for wakeup if data is not yet available.

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

# Return value

The function returns:

- `Poll::Pending` if data is not yet available.
- `Poll::Ready(Ok(n))` if data is available. `n` is the number of bytes peeked.
- `Poll::Ready(Err(e))` if an error is encountered.

# Errors

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

# Examples

    use tokio::io::{self, ReadBuf};
    use tokio::net::TcpStream;

    use futures::future::poll_fn;

    #[tokio::main]
    async fn main() -> io::Result<()> {
        let stream = TcpStream::connect("127.0.0.1:8000").await?;
        let mut buf = [0; 10];
        let mut buf = ReadBuf::new(&mut buf);

        poll_fn(|cx| {
            stream.poll_peek(cx, &mut buf)
        }).await?;

        Ok(())
    }

#### `pub async fn ready<'_>(&'_ self, interest: Interest) -> Result<Ready>` [src]

Wait 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.

# Examples

Concurrently read and write to the stream on the same task without splitting.

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

    #[tokio::main]
    async fn main() -> Result<(), Box<dyn Error>> {
        let stream = TcpStream::connect("127.0.0.1:8080").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<()>` [src]

Wait for the socket to become readable.

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

# Examples

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

    #[tokio::main]
    async fn main() -> Result<(), Box<dyn Error>> {
        // Connect to a peer
        let stream = TcpStream::connect("127.0.0.1:8080").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<()>>` [src]

Polls for read readiness.

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

Note that on multiple calls to `poll_read_ready`, `poll_read` or `poll_peek`, 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 tcp stream is not ready for reading.
- `Poll::Ready(Ok(()))` if the tcp 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>` [src]

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. `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::TcpStream;
    use std::error::Error;
    use std::io;

    #[tokio::main]
    async fn main() -> Result<(), Box<dyn Error>> {
        // Connect to a peer
        let stream = TcpStream::connect("127.0.0.1:8080").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 async fn writable<'_>(&'_ self) -> Result<()>` [src]

Wait for the socket to become writable.

This function is equivalent to `ready(Interest::WRITABLE)` and is usually paired with `try_write()`.

# Examples

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

    #[tokio::main]
    async fn main() -> Result<(), Box<dyn Error>> {
        // Connect to a peer
        let stream = TcpStream::connect("127.0.0.1:8080").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<()>>` [src]

Polls for write readiness.

If the tcp stream is not currently ready for writing, this method will store a clone of the `Waker` from the provided `Context`. When the tcp 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 tcp stream is not ready for writing.
- `Poll::Ready(Ok(()))` if the tcp 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>` [src]

Try 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::TcpStream;
    use std::error::Error;
    use std::io;

    #[tokio::main]
    async fn main() -> Result<(), Box<dyn Error>> {
        // Connect to a peer
        let stream = TcpStream::connect("127.0.0.1:8080").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 async fn peek<'_, '_>(&'_ self, buf: &'_ mut [u8]) -> Result<usize>` [src]

Receives data on the socket from the remote address to which it is connected, without removing that data from the queue. On success, returns the number of bytes peeked.

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

# Examples

    use tokio::net::TcpStream;
    use tokio::io::AsyncReadExt;
    use std::error::Error;

    #[tokio::main]
    async fn main() -> Result<(), Box<dyn Error>> {
        // Connect to a peer
        let mut stream = TcpStream::connect("127.0.0.1:8080").await?;

        let mut b1 = [0; 10];
        let mut b2 = [0; 10];

        // Peek at the data
        let n = stream.peek(&mut b1).await?;

        // Read the data
        assert_eq!(n, stream.read(&mut b2[..n]).await?);
        assert_eq!(&b1[..n], &b2[..n]);

        Ok(())
    }

The `read` method is defined on the `AsyncReadExt` trait.

#### `pub fn nodelay(&self) -> Result<bool>` [src]

Gets the value of the `TCP_NODELAY` option on this socket.

For more information about this option, see `set_nodelay`.

# Examples

    use tokio::net::TcpStream;

    let stream = TcpStream::connect("127.0.0.1:8080").await?;

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

#### `pub fn set_nodelay(&self, nodelay: bool) -> Result<()>` [src]

Sets the value of the `TCP_NODELAY` option on this socket.

If set, this option disables the Nagle algorithm. This means that segments are always sent as soon as possible, even if there is only a small amount of data. When not set, data is buffered until there is a sufficient amount to send out, thereby avoiding the frequent sending of small packets.

# Examples

    use tokio::net::TcpStream;

    let stream = TcpStream::connect("127.0.0.1:8080").await?;

    stream.set_nodelay(true)?;

#### `pub fn linger(&self) -> Result<Option<Duration>>` [src]

Reads the linger duration for this socket by getting the `SO_LINGER` option.

For more information about this option, see `set_linger`.

# Examples

    use tokio::net::TcpStream;

    let stream = TcpStream::connect("127.0.0.1:8080").await?;

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

#### `pub fn set_linger(&self, dur: Option<Duration>) -> Result<()>` [src]

Sets the linger duration of this socket by setting the SO_LINGER option.

This option controls the action taken when a stream has unsent messages and the stream is closed. If SO_LINGER is set, the system shall block the process until it can transmit the data or until the time expires.

If SO_LINGER is not specified, and the stream is closed, the system handles the call in a way that allows the process to continue as quickly as possible.

# Examples

    use tokio::net::TcpStream;

    let stream = TcpStream::connect("127.0.0.1:8080").await?;

    stream.set_linger(None)?;

#### `pub fn ttl(&self) -> Result<u32>` [src]

Gets the value of the `IP_TTL` option for this socket.

For more information about this option, see `set_ttl`.

# Examples

    use tokio::net::TcpStream;

    let stream = TcpStream::connect("127.0.0.1:8080").await?;

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

#### `pub fn set_ttl(&self, ttl: u32) -> Result<()>` [src]

Sets the value for the `IP_TTL` option on this socket.

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

# Examples

    use tokio::net::TcpStream;

    let stream = TcpStream::connect("127.0.0.1:8080").await?;

    stream.set_ttl(123)?;

#### `pub fn split<'a>(&'a mut self) -> (ReadHalf<'a>, WriteHalf<'a>)` [src]

Splits a `TcpStream` 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)` [src]

Splits a `TcpStream` 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 TCP stream. This is equivalent to calling `shutdown()` on the `TcpStream`.

## Trait Implementations

### `impl AsRawFd for TcpStream` [src]

#### `fn as_raw_fd(&self) -> RawFd` [src]

Extracts the raw file descriptor. Read more

### `impl<'_> AsRef<TcpStream> for ReadHalf<'_>` [src]

#### `fn as_ref(&self) -> &TcpStream` [src]

Performs the conversion.

### `impl<'_> AsRef<TcpStream> for WriteHalf<'_>` [src]

#### `fn as_ref(&self) -> &TcpStream` [src]

Performs the conversion.

### `impl AsRef<TcpStream> for OwnedReadHalf` [src]

#### `fn as_ref(&self) -> &TcpStream` [src]

Performs the conversion.

### `impl AsRef<TcpStream> for OwnedWriteHalf` [src]

#### `fn as_ref(&self) -> &TcpStream` [src]

Performs the conversion.

### `impl AsyncRead for TcpStream` [src]

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

Attempts to read from the `AsyncRead` into `buf`. Read more

### `impl AsyncWrite for TcpStream` [src]

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

Attempt to write bytes from `buf` into the object. Read more

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

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

#### `fn is_write_vectored(&self) -> bool` [src]

Determines if this writer has an efficient `poll_write_vectored` implementation. Read more

#### `fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Result<()>>` [src]

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

#### `fn poll_shutdown(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Result<()>>` [src]

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

### `impl Debug for TcpStream` [src]

#### `fn fmt(&self, f: &mut Formatter<'_>) -> Result` [src]

Formats the value using the given formatter. Read more

### `impl TryFrom<TcpStream> for TcpStream` [src]

#### `type Error = Error`

The type returned in the event of a conversion error.

#### `fn try_from(stream: TcpStream) -> Result<Self, Self::Error>` [src]

Consumes stream, returning the tokio I/O object.

This is equivalent to `TcpStream::from_std(stream)`.

## Auto Trait Implementations

### `impl !RefUnwindSafe for TcpStream`

### `impl Send for TcpStream`

### `impl Sync for TcpStream`

### `impl Unpin for TcpStream`

### `impl !UnwindSafe for TcpStream`

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `pub fn type_id(&self) -> TypeId` [src]

Gets the `TypeId` of `self`. Read more

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow(&self) -> &Tⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;`
` [src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow_mut(&mut self) -> &mut Tⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;`
` [src]

Mutably borrows from an owned value. Read more

### `impl<T> From<T> for T` [src]

#### `pub fn from(t: T) -> T` [src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `pub fn into(self) -> U` [src]

Performs the conversion.

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>` [src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.

#### `pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>` [src]

Performs the conversion.