pub struct TcpListener { /* private fields */ }
Available on crate features async-networking and net only.
Expand description

A TCP socket server, listening for connections.

You can accept a new connection by using the accept method.

A TcpListener can be turned into a Stream with TcpListenerStream.

Errors

Note that accepting a connection can lead to various errors and not all of them are necessarily fatal ‒ for example having too many open file descriptors or the other side closing the connection while it waits in an accept queue. These would terminate the stream if not handled in any way.

Examples

Using accept:

use tokio::net::TcpListener;

use std::io;

async fn process_socket<T>(socket: T) {
    // do work with socket here
}

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

    loop {
        let (socket, _) = listener.accept().await?;
        process_socket(socket).await;
    }
}

Implementations§

Available on non-tokio_wasi only.

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 implementor 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.

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

    Ok(())
}

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 the event in a tokio::select! statement and some other 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(())
}

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.

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. The conversion assumes nothing about the underlying listener; it is left up to the user to set it in non-blocking mode.

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.

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.

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(())
}

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(())
}

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(())
}

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(())
}

Trait Implementations§

Extracts the raw file descriptor. Read more
Formats the value using the given formatter. Read more

Consumes stream, returning the tokio I/O object.

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

The type returned in the event of a conversion error.

Auto Trait Implementations§

Blanket Implementations§

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
Instruments this type with the current Span, returning an Instrumented wrapper. Read more

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

Should always be Self
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.
Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more