Struct tokio::net::TcpSocket

pub struct TcpSocket { /* fields omitted */ }

A TCP socket that has not yet been converted to a TcpStream or TcpListener.

TcpSocket wraps an operating system socket and enables the caller to configure the socket before establishing a TCP connection or accepting inbound connections. The caller is able to set socket option and explicitly bind the socket with a socket address.

The underlying socket is closed when the TcpSocket value is dropped.

TcpSocket should only be used directly if the default configuration used by TcpStream::connect and TcpListener::bind does not meet the required use case.

Calling TcpStream::connect("127.0.0.1:8080") is equivalent to:

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();

    let socket = TcpSocket::new_v4()?;
    let stream = socket.connect(addr).await?;

    Ok(())
}

Calling TcpListener::bind("127.0.0.1:8080") is equivalent to:

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();

    let socket = TcpSocket::new_v4()?;
    // On platforms with Berkeley-derived sockets, this allows to quickly
    // rebind a socket, without needing to wait for the OS to clean up the
    // previous one.
    //
    // On Windows, this allows rebinding sockets which are actively in use,
    // which allows “socket hijacking”, so we explicitly don't set it here.
    // https://docs.microsoft.com/en-us/windows/win32/winsock/using-so-reuseaddr-and-so-exclusiveaddruse
    socket.set_reuseaddr(true)?;
    socket.bind(addr)?;

    let listener = socket.listen(1024)?;

    Ok(())
}

Setting socket options not explicitly provided by TcpSocket may be done by accessing the RawFd/RawSocket using AsRawFd/AsRawSocket and setting the option with a crate like socket2.

Implementations

impl TcpSocket

pub fn new_v4() -> Result<TcpSocket>

Create a new socket configured for IPv4.

Calls socket(2) with AF_INET and SOCK_STREAM.

Returns

On success, the newly created TcpSocket is returned. If an error is encountered, it is returned instead.

Examples

Create a new IPv4 socket and start listening.

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();
    let socket = TcpSocket::new_v4()?;
    socket.bind(addr)?;

    let listener = socket.listen(128)?;
    Ok(())
}

pub fn new_v6() -> Result<TcpSocket>

Create a new socket configured for IPv6.

Calls socket(2) with AF_INET6 and SOCK_STREAM.

Returns

On success, the newly created TcpSocket is returned. If an error is encountered, it is returned instead.

Examples

Create a new IPv6 socket and start listening.

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "[::1]:8080".parse().unwrap();
    let socket = TcpSocket::new_v6()?;
    socket.bind(addr)?;

    let listener = socket.listen(128)?;
    Ok(())
}

pub fn set_reuseaddr(&self, reuseaddr: bool) -> Result<()>

Allow the socket to bind to an in-use address.

Behavior is platform specific. Refer to the target platform’s documentation for more details.

Examples

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();

    let socket = TcpSocket::new_v4()?;
    socket.set_reuseaddr(true)?;
    socket.bind(addr)?;

    let listener = socket.listen(1024)?;

    Ok(())
}

pub fn reuseaddr(&self) -> Result<bool>

Retrieves the value set for SO_REUSEADDR on this socket

Examples

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();

    let socket = TcpSocket::new_v4()?;
    socket.set_reuseaddr(true)?;
    assert!(socket.reuseaddr().unwrap());
    socket.bind(addr)?;

    let listener = socket.listen(1024)?;
    Ok(())
}

pub fn set_reuseport(&self, reuseport: bool) -> Result<()>

Allow the socket to bind to an in-use port. Only available for unix systems (excluding Solaris & Illumos).

Behavior is platform specific. Refer to the target platform’s documentation for more details.

Examples

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();

    let socket = TcpSocket::new_v4()?;
    socket.set_reuseport(true)?;
    socket.bind(addr)?;

    let listener = socket.listen(1024)?;
    Ok(())
}

pub fn reuseport(&self) -> Result<bool>

Allow the socket to bind to an in-use port. Only available for unix systems (excluding Solaris & Illumos).

Behavior is platform specific. Refer to the target platform’s documentation for more details.

Examples

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();

    let socket = TcpSocket::new_v4()?;
    socket.set_reuseport(true)?;
    assert!(socket.reuseport().unwrap());
    socket.bind(addr)?;

    let listener = socket.listen(1024)?;
    Ok(())
}

pub fn set_send_buffer_size(&self, size: u32) -> Result<()>

Sets the size of the TCP send buffer on this socket.

On most operating systems, this sets the SO_SNDBUF socket option.

pub fn send_buffer_size(&self) -> Result<u32>

Returns the size of the TCP send buffer for this socket.

On most operating systems, this is the value of the SO_SNDBUF socket option.

Note that if set_send_buffer_size has been called on this socket previously, the value returned by this function may not be the same as the argument provided to set_send_buffer_size. This is for the following reasons:

• Most operating systems have minimum and maximum allowed sizes for the send buffer, and will clamp the provided value if it is below the minimum or above the maximum. The minimum and maximum buffer sizes are OS-dependent.
• Linux will double the buffer size to account for internal bookkeeping data, and returns the doubled value from getsockopt(2). As per man 7 socket:

  Sets or gets the maximum socket send buffer in bytes. The kernel doubles this value (to allow space for bookkeeping overhead) when it is set using setsockopt(2), and this doubled value is returned by getsockopt(2).

pub fn set_recv_buffer_size(&self, size: u32) -> Result<()>

Sets the size of the TCP receive buffer on this socket.

On most operating systems, this sets the SO_RCVBUF socket option.

pub fn recv_buffer_size(&self) -> Result<u32>

Returns the size of the TCP receive buffer for this socket.

On most operating systems, this is the value of the SO_RCVBUF socket option.

Note that if set_recv_buffer_size has been called on this socket previously, the value returned by this function may not be the same as the argument provided to set_send_buffer_size. This is for the following reasons:

• Most operating systems have minimum and maximum allowed sizes for the receive buffer, and will clamp the provided value if it is below the minimum or above the maximum. The minimum and maximum buffer sizes are OS-dependent.
• Linux will double the buffer size to account for internal bookkeeping data, and returns the doubled value from getsockopt(2). As per man 7 socket:

  Sets or gets the maximum socket send buffer in bytes. The kernel doubles this value (to allow space for bookkeeping overhead) when it is set using setsockopt(2), and this doubled value is returned by getsockopt(2).

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

Get the local address of this socket.

Will fail on windows if called before bind.

Examples

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();

    let socket = TcpSocket::new_v4()?;
    socket.bind(addr)?;
    assert_eq!(socket.local_addr().unwrap().to_string(), "127.0.0.1:8080");
    let listener = socket.listen(1024)?;
    Ok(())
}

pub fn bind(&self, addr: SocketAddr) -> Result<()>

Bind the socket to the given address.

This calls the bind(2) operating-system function. Behavior is platform specific. Refer to the target platform’s documentation for more details.

Examples

Bind a socket before listening.

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();

    let socket = TcpSocket::new_v4()?;
    socket.bind(addr)?;

    let listener = socket.listen(1024)?;

    Ok(())
}

pub async fn connect(self, addr: SocketAddr) -> Result<TcpStream>

Establish a TCP connection with a peer at the specified socket address.

The TcpSocket is consumed. Once the connection is established, a connected TcpStream is returned. If the connection fails, the encountered error is returned.

This calls the connect(2) operating-system function. Behavior is platform specific. Refer to the target platform’s documentation for more details.

Examples

Connecting to a peer.

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();

    let socket = TcpSocket::new_v4()?;
    let stream = socket.connect(addr).await?;

    Ok(())
}

pub fn listen(self, backlog: u32) -> Result<TcpListener>

Convert the socket into a TcpListener.

backlog defines the maximum number of pending connections are queued by the operating system at any given time. Connection are removed from the queue with TcpListener::accept. When the queue is full, the operationg-system will start rejecting connections.

This calls the listen(2) operating-system function, marking the socket as a passive socket. Behavior is platform specific. Refer to the target platform’s documentation for more details.

Examples

Create a TcpListener.

use tokio::net::TcpSocket;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();

    let socket = TcpSocket::new_v4()?;
    socket.bind(addr)?;

    let listener = socket.listen(1024)?;

    Ok(())
}

Trait Implementations

impl AsRawFd for TcpSocket

fn as_raw_fd(&self) -> RawFd

Extracts the raw file descriptor.

impl Debug for TcpSocket

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

Formats the value using the given formatter.

impl FromRawFd for TcpSocket

unsafe fn from_raw_fd(fd: RawFd) -> TcpSocket

Converts a RawFd to a TcpSocket.

Notes

The caller is responsible for ensuring that the socket is in non-blocking mode.