path: root/tokio/src/net/udp/socket.rs

use crate::io::PollEvented;
use crate::net::{to_socket_addrs, ToSocketAddrs};

use std::convert::TryFrom;
use std::fmt;
use std::io;
use std::net::{self, Ipv4Addr, Ipv6Addr, SocketAddr};

cfg_net! {
    /// A UDP socket
    ///
    /// UDP is "connectionless", unlike TCP. Meaning, regardless of what address you've bound to, a `UdpSocket`
    /// is free to communicate with many different remotes. In tokio there are basically two main ways to use `UdpSocket`:
    ///
    /// * one to many: [`bind`](`UdpSocket::bind`) and use [`send_to`](`UdpSocket::send_to`)
    ///   and [`recv_from`](`UdpSocket::recv_from`) to communicate with many different addresses
    /// * one to one: [`connect`](`UdpSocket::connect`) and associate with a single address, using [`send`](`UdpSocket::send`)
    ///   and [`recv`](`UdpSocket::recv`) to communicate only with that remote address
    ///
    /// `UdpSocket` can also be used concurrently to `send_to` and `recv_from` in different tasks,
    /// all that's required is that you `Arc<UdpSocket>` and clone a reference for each task.
    ///
    /// # Streams
    ///
    /// If you need to listen over UDP and produce a [`Stream`](`crate::stream::Stream`), you can look
    /// at [`UdpFramed`].
    ///
    /// [`UdpFramed`]: https://docs.rs/tokio-util/latest/tokio_util/udp/struct.UdpFramed.html
    ///
    /// # Example: one to many (bind)
    ///
    /// Using `bind` we can create a simple echo server that sends and recv's with many different clients:
    /// ```no_run
    /// use tokio::net::UdpSocket;
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> io::Result<()> {
    ///     let sock = UdpSocket::bind("0.0.0.0:8080").await?;
    ///     let mut buf = [0; 1024];
    ///     loop {
    ///         let (len, addr) = sock.recv_from(&mut buf).await?;
    ///         println!("{:?} bytes received from {:?}", len, addr);
    ///
    ///         let len = sock.send_to(&buf[..len], addr).await?;
    ///         println!("{:?} bytes sent", len);
    ///     }
    /// }
    /// ```
    ///
    /// # Example: one to one (connect)
    ///
    /// Or using `connect` we can echo with a single remote address using `send` and `recv`:
    /// ```no_run
    /// use tokio::net::UdpSocket;
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> io::Result<()> {
    ///     let sock = UdpSocket::bind("0.0.0.0:8080").await?;
    ///
    ///     let remote_addr = "127.0.0.1:59611";
    ///     sock.connect(remote_addr).await?;
    ///     let mut buf = [0; 1024];
    ///     loop {
    ///         let len = sock.recv(&mut buf).await?;
    ///         println!("{:?} bytes received from {:?}", len, remote_addr);
    ///
    ///         let len = sock.send(&buf[..len]).await?;
    ///         println!("{:?} bytes sent", len);
    ///     }
    /// }
    /// ```
    ///
    /// # Example: Sending/Receiving concurrently
    ///
    /// Because `send_to` and `recv_from` take `&self`. It's perfectly alright to `Arc<UdpSocket>`
    /// and share the references to multiple tasks, in order to send/receive concurrently. Here is
    /// a similar "echo" example but that supports concurrent sending/receiving:
    ///
    /// ```no_run
    /// use tokio::{net::UdpSocket, sync::mpsc};
    /// use std::{io, net::SocketAddr, sync::Arc};
    ///
    /// #[tokio::main]
    /// async fn main() -> io::Result<()> {
    ///     let sock = UdpSocket::bind("0.0.0.0:8080".parse::<SocketAddr>().unwrap()).await?;
    ///     let r = Arc::new(sock);
    ///     let s = r.clone();
    ///     let (tx, mut rx) = mpsc::channel::<(Vec<u8>, SocketAddr)>(1_000);
    ///
    ///     tokio::spawn(async move {
    ///         while let Some((bytes, addr)) = rx.recv().await {
    ///             let len = s.send_to(&bytes, &addr).await.unwrap();
    ///             println!("{:?} bytes sent", len);
    ///         }
    ///     });
    ///
    ///     let mut buf = [0; 1024];
    ///     loop {
    ///         let (len, addr) = r.recv_from(&mut buf).await?;
    ///         println!("{:?} bytes received from {:?}", len, addr);
    ///         tx.send((buf[..len].to_vec(), addr)).await.unwrap();
    ///     }
    /// }
    /// ```
    ///
    pub struct UdpSocket {
        io: PollEvented<mio::net::UdpSocket>,
    }
}

impl UdpSocket {
    /// This function will create a new UDP socket and attempt to bind it to
    /// the `addr` provided.
    ///
    /// # Example
    ///
    /// ```no_run
    /// use tokio::net::UdpSocket;
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> io::Result<()> {
    ///     let sock = UdpSocket::bind("0.0.0.0:8080").await?;
    ///     // use `sock`
    /// #   let _ = sock;
    ///     Ok(())
    /// }
    /// ```
    pub async fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<UdpSocket> {
        let addrs = to_socket_addrs(addr).await?;
        let mut last_err = None;

        for addr in addrs {
            match UdpSocket::bind_addr(addr) {
                Ok(socket) => return Ok(socket),
                Err(e) => last_err = Some(e),
            }
        }

        Err(last_err.unwrap_or_else(|| {
            io::Error::new(
                io::ErrorKind::InvalidInput,
                "could not resolve to any address",
            )
        }))
    }

    fn bind_addr(addr: SocketAddr) -> io::Result<UdpSocket> {
        let sys = mio::net::UdpSocket::bind(addr)?;
        UdpSocket::new(sys)
    }

    fn new(socket: mio::net::UdpSocket) -> io::Result<UdpSocket> {
        let io = PollEvented::new(socket)?;
        Ok(UdpSocket { io })
    }

    /// Creates a new `UdpSocket` from the previously bound socket provided.
    ///
    /// The socket given will be registered with the event loop that `handle`
    /// is associated with. This function requires that `socket` has previously
    /// been bound to an address to work correctly.
    ///
    /// This can be used in conjunction with net2's `UdpBuilder` interface to
    /// configure a socket before it's handed off, such as setting options like
    /// `reuse_address` or binding to multiple addresses.
    ///
    /// # 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`](crate::runtime::Runtime::enter) function.
    ///
    /// # Example
    ///
    /// ```no_run
    /// use tokio::net::UdpSocket;
    /// # use std::{io, net::SocketAddr};
    ///
    /// # #[tokio::main]
    /// # async fn main() -> io::Result<()> {
    /// let addr = "0.0.0.0:8080".parse::<SocketAddr>().unwrap();
    /// let std_sock = std::net::UdpSocket::bind(addr)?;
    /// let sock = UdpSocket::from_std(std_sock)?;
    /// // use `sock`
    /// # Ok(())
    /// # }
    /// ```
    pub fn from_std(socket: net::UdpSocket) -> io::Result<UdpSocket> {
        let io = mio::net::UdpSocket::from_std(socket);
        UdpSocket::new(io)
    }

    /// Returns the local address that this socket is bound to.
    ///
    /// # Example
    ///
    /// ```no_run
    /// use tokio::net::UdpSocket;
    /// # use std::{io, net::SocketAddr};
    ///
    /// # #[tokio::main]
    /// # async fn main() -> io::Result<()> {
    /// let addr = "0.0.0.0:8080".parse::<SocketAddr>().unwrap();
    /// let sock = UdpSocket::bind(addr).await?;
    /// // the address the socket is bound to
    /// let local_addr = sock.local_addr()?;
    /// # Ok(())
    /// # }
    /// ```
    pub fn local_addr(&self) -> io::Result<SocketAddr> {
        self.io.get_ref().local_addr()
    }

    /// Connects the UDP socket setting the default destination for send() and
    /// limiting packets that are read via recv from the address specified in
    /// `addr`.
    ///
    /// # Example
    ///
    /// ```no_run
    /// use tokio::net::UdpSocket;
    /// # use std::{io, net::SocketAddr};
    ///
    /// # #[tokio::main]
    /// # async fn main() -> io::Result<()> {
    /// let sock = UdpSocket::bind("0.0.0.0:8080".parse::<SocketAddr>().unwrap()).await?;
    ///
    /// let remote_addr = "127.0.0.1:59600".parse::<SocketAddr>().unwrap();
    /// sock.connect(remote_addr).await?;
    /// let mut buf = [0u8; 32];
    /// // recv from remote_addr
    /// let len = sock.recv(&mut buf).await?;
    /// // send to remote_addr
    /// let _len = sock.send(&buf[..len]).await?;
    /// # Ok(())
    /// # }
    /// ```
    pub async fn connect<A: ToSocketAddrs>(&self, addr: A) -> io::Result<()> {
        let addrs = to_socket_addrs(addr).await?;
        let mut last_err = None;

        for addr in addrs {
            match self.io.get_ref().connect(addr) {
                Ok(_) => return Ok(()),
                Err(e) => last_err = Some(e),
            }
        }

        Err(last_err.unwrap_or_else(|| {
            io::Error::new(
                io::ErrorKind::InvalidInput,
                "could not resolve to any address",
            )
        }))
    }

    /// Returns a future that sends data on the socket to the remote address to which it is connected.
    /// On success, the future will resolve to the number of bytes written.
    ///
    /// The [`connect`] method will connect this socket to a remote address. The future
    /// will resolve to an error if the socket is not connected.
    ///
    /// [`connect`]: method@Self::connect
    pub async fn send(&self, buf: &[u8]) -> io::Result<usize> {
        self.io
            .async_io(mio::Interest::WRITABLE, |sock| sock.send(buf))
            .await
    }

    /// Try to send data on the socket to the remote address to which it is
    /// connected.
    ///
    /// # Returns
    ///
    /// If successfull, the number of bytes sent is returned. Users
    /// should ensure that when the remote cannot receive, the
    /// [`ErrorKind::WouldBlock`] is properly handled.
    ///
    /// [`ErrorKind::WouldBlock`]: std::io::ErrorKind::WouldBlock
    pub fn try_send(&self, buf: &[u8]) -> io::Result<usize> {
        self.io.get_ref().send(buf)
    }

    /// Returns a future that receives a single datagram message on the socket from
    /// the remote address to which it is connected. On success, the future will resolve
    /// to the number of bytes read.
    ///
    /// The function must be called with valid byte array `buf` of sufficient size to
    /// hold the message bytes. If a message is too long to fit in the supplied buffer,
    /// excess bytes may be discarded.
    ///
    /// The [`connect`] method will connect this socket to a remote address. The future
    /// will fail if the socket is not connected.
    ///
    /// [`connect`]: method@Self::connect
    pub async fn recv(&self, buf: &mut [u8]) -> io::Result<usize> {