impl TcpListener

async fn bind<A: ToSocketAddrs>(addr: A) -> Result<TcpListener>

Creates a new TcpListener, which will be bound to the specified address.

The returned listener is ready for accepting connections.

Binding with a port number of 0 will request that the OS assigns a port to this listener. The port allocated can be queried via the local_addr method.

The address type can be any implementer of the ToSocketAddrs trait. If addr yields multiple addresses, bind will be attempted with each of the addresses until one succeeds and returns the listener. If none of the addresses succeed in creating a listener, the error returned from the last attempt (the last address) is returned.

This function sets the SO_REUSEADDR option on the socket on Unix.

To configure the socket before binding, you can use the TcpSocket type.

Examples

use tokio::net::TcpListener;
use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let listener = TcpListener::bind("127.0.0.1:2345").await?;

    // use the listener

    # let _ = listener;
    Ok(())
}

async fn accept(&self) -> Result<(TcpStream, SocketAddr)>

Accepts a new incoming connection from this listener.

This function will yield once a new TCP connection is established. When established, the corresponding TcpStream and the remote peer's address will be returned.

Cancel safety

This method is cancel safe. If the method is used as a branch in tokio::select! and another branch completes first, then it is guaranteed that no new connections were accepted by this method.

Examples

use tokio::net::TcpListener;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let listener = TcpListener::bind("127.0.0.1:8080").await?;

    match listener.accept().await {
        Ok((_socket, addr)) => println!("new client: {:?}", addr),
        Err(e) => println!("couldn't get client: {:?}", e),
    }

    Ok(())
}

fn poll_accept(&self, cx: &mut Context<'_>) -> Poll<Result<(TcpStream, SocketAddr)>>

Polls to accept a new incoming connection to this listener.

If there is no connection to accept, Poll::Pending is returned and the current task will be notified by a waker. Note that on multiple calls to poll_accept, only the Waker from the Context passed to the most recent call is scheduled to receive a wakeup.

fn from_std(listener: TcpListener) -> Result<TcpListener>

Creates new TcpListener from a std::net::TcpListener.

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

This API is typically paired with the socket2 crate and the Socket type to build up and customize a listener before it's shipped off to the backing event loop. This allows configuration of options like SO_REUSEPORT, binding to multiple addresses, etc.

Notes

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

Passing a listener in blocking mode is always erroneous, and the behavior in that case may change in the future. For example, it could panic.

Examples

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

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let std_listener = std::net::TcpListener::bind("127.0.0.1:0")?;
    std_listener.set_nonblocking(true)?;
    let listener = TcpListener::from_std(std_listener)?;
    Ok(())
}

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.

fn into_std(self) -> Result<TcpListener>

Turns a tokio::net::TcpListener into a std::net::TcpListener.

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

Examples

use std::error::Error;

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let tokio_listener = tokio::net::TcpListener::bind("127.0.0.1:0").await?;
    let std_listener = tokio_listener.into_std()?;
    std_listener.set_nonblocking(false)?;
    Ok(())
}

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

Returns the local address that this listener is bound to.

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

Examples

use tokio::net::TcpListener;

use std::io;
use std::net::{Ipv4Addr, SocketAddr, SocketAddrV4};

#[tokio::main]
async fn main() -> io::Result<()> {
    let listener = TcpListener::bind("127.0.0.1:8080").await?;

    assert_eq!(listener.local_addr()?,
               SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080)));

    Ok(())
}

fn ttl(&self) -> Result<u32>

Gets the value of the IP_TTL option for this socket.

For more information about this option, see set_ttl.

Examples

use tokio::net::TcpListener;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
   let listener = TcpListener::bind("127.0.0.1:0").await?;

   listener.set_ttl(100).expect("could not set TTL");
   assert_eq!(listener.ttl()?, 100);

   Ok(())
}

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

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::TcpListener;

use std::io;

#[tokio::main]
async fn main() -> io::Result<()> {
    let listener = TcpListener::bind("127.0.0.1:0").await?;

    listener.set_ttl(100).expect("could not set TTL");

    Ok(())
}