Struct UdpSocket

pub struct UdpSocket { /* private fields */ }

A User Datagram Protocol socket.

This is an implementation of a bound UDP socket. This supports both IPv4 and IPv6 addresses, and there is no corresponding notion of a server because UDP is a datagram protocol.

Examples

// An Echo program:
// SENDER -> sends a message.
// ECHOER -> listens and prints the message received.

use mio::net::UdpSocket;
use mio::{Events, Interest, Poll, Token};
use std::time::Duration;

const SENDER: Token = Token(0);
const ECHOER: Token = Token(1);

// This operation will fail if the address is in use, so we select different ports for each
// socket.
let mut sender_socket = UdpSocket::bind("127.0.0.1:0".parse()?)?;
let mut echoer_socket = UdpSocket::bind("127.0.0.1:0".parse()?)?;

// If we do not use connect here, SENDER and ECHOER would need to call send_to and recv_from
// respectively.
sender_socket.connect(echoer_socket.local_addr()?)?;

// We need a Poll to check if SENDER is ready to be written into, and if ECHOER is ready to be
// read from.
let mut poll = Poll::new()?;

// We register our sockets here so that we can check if they are ready to be written/read.
poll.registry().register(&mut sender_socket, SENDER, Interest::WRITABLE)?;
poll.registry().register(&mut echoer_socket, ECHOER, Interest::READABLE)?;

let msg_to_send = [9; 9];
let mut buffer = [0; 9];

let mut events = Events::with_capacity(128);
loop {
    poll.poll(&mut events, Some(Duration::from_millis(100)))?;
    for event in events.iter() {
        match event.token() {
            // Our SENDER is ready to be written into.
            SENDER => {
                let bytes_sent = sender_socket.send(&msg_to_send)?;
                assert_eq!(bytes_sent, 9);
                println!("sent {:?} -> {:?} bytes", msg_to_send, bytes_sent);
            },
            // Our ECHOER is ready to be read from.
            ECHOER => {
                let num_recv = echoer_socket.recv(&mut buffer)?;
                println!("echo {:?} -> {:?}", buffer, num_recv);
                buffer = [0; 9];
            }
            _ => unreachable!()
        }
    }
}

Implementations

impl UdpSocket

pub fn bind(addr: SocketAddr) -> Result<UdpSocket>

Creates a UDP socket from the given address.

Examples

use mio::net::UdpSocket;

// We must bind it to an open address.
let socket = match UdpSocket::bind("127.0.0.1:0".parse()?) {
    Ok(new_socket) => new_socket,
    Err(fail) => {
        // We panic! here, but you could try to bind it again on another address.
        panic!("Failed to bind socket. {:?}", fail);
    }
};

// Our socket was created, but we should not use it before checking it's readiness.

pub fn from_std(socket: UdpSocket) -> UdpSocket

Creates a new UdpSocket from a standard net::UdpSocket.

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

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

Returns the socket address that this socket was created from.

Examples

use mio::net::UdpSocket;

let addr = "127.0.0.1:0".parse()?;
let socket = UdpSocket::bind(addr)?;
assert_eq!(socket.local_addr()?.ip(), addr.ip());

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

Returns the socket address of the remote peer this socket was connected to.

Examples

use mio::net::UdpSocket;

let addr = "127.0.0.1:0".parse()?;
let peer_addr = "127.0.0.1:11100".parse()?;
let socket = UdpSocket::bind(addr)?;
socket.connect(peer_addr)?;
assert_eq!(socket.peer_addr()?.ip(), peer_addr.ip());

pub fn send_to(&self, buf: &[u8], target: SocketAddr) -> Result<usize>

Sends data on the socket to the given address. On success, returns the number of bytes written.

Address type can be any implementor of ToSocketAddrs trait. See its documentation for concrete examples.

Examples

use mio::net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:0".parse()?)?;

// We must check if the socket is writable before calling send_to,
// or we could run into a WouldBlock error.

let bytes_sent = socket.send_to(&[9; 9], "127.0.0.1:11100".parse()?)?;
assert_eq!(bytes_sent, 9);

pub fn recv_from(&self, buf: &mut [u8]) -> Result<(usize, SocketAddr)>

Receives data from the socket. On success, returns the number of bytes read and the address from whence the data came.

Notes

On Windows, if the data is larger than the buffer specified, the buffer is filled with the first part of the data, and recv_from returns the error WSAEMSGSIZE(10040). The excess data is lost. Make sure to always use a sufficiently large buffer to hold the maximum UDP packet size, which can be up to 65536 bytes in size.

Examples

use mio::net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:0".parse()?)?;

// We must check if the socket is readable before calling recv_from,
// or we could run into a WouldBlock error.

let mut buf = [0; 9];
let (num_recv, from_addr) = socket.recv_from(&mut buf)?;
println!("Received {:?} -> {:?} bytes from {:?}", buf, num_recv, from_addr);

pub fn peek_from(&self, buf: &mut [u8]) -> Result<(usize, SocketAddr)>

Receives data from the socket, without removing it from the input queue. On success, returns the number of bytes read and the address from whence the data came.

Notes

On Windows, if the data is larger than the buffer specified, the buffer is filled with the first part of the data, and peek_from returns the error WSAEMSGSIZE(10040). The excess data is lost. Make sure to always use a sufficiently large buffer to hold the maximum UDP packet size, which can be up to 65536 bytes in size.

Examples

use mio::net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:0".parse()?)?;

// We must check if the socket is readable before calling recv_from,
// or we could run into a WouldBlock error.

let mut buf = [0; 9];
let (num_recv, from_addr) = socket.peek_from(&mut buf)?;
println!("Received {:?} -> {:?} bytes from {:?}", buf, num_recv, from_addr);

pub fn send(&self, buf: &[u8]) -> Result<usize>

Sends data on the socket to the address previously bound via connect(). On success, returns the number of bytes written.

pub fn recv(&self, buf: &mut [u8]) -> Result<usize>

Receives data from the socket previously bound with connect(). On success, returns the number of bytes read.

Notes

On Windows, if the data is larger than the buffer specified, the buffer is filled with the first part of the data, and recv returns the error WSAEMSGSIZE(10040). The excess data is lost. Make sure to always use a sufficiently large buffer to hold the maximum UDP packet size, which can be up to 65536 bytes in size.

pub fn peek(&self, buf: &mut [u8]) -> Result<usize>

Receives data from the socket, without removing it from the input queue. On success, returns the number of bytes read.

Notes

On Windows, if the data is larger than the buffer specified, the buffer is filled with the first part of the data, and peek returns the error WSAEMSGSIZE(10040). The excess data is lost. Make sure to always use a sufficiently large buffer to hold the maximum UDP packet size, which can be up to 65536 bytes in size.

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

Connects the UDP socket setting the default destination for send() and limiting packets that are read via recv from the address specified in addr.

This may return a WouldBlock in which case the socket connection cannot be completed immediately, it usually means there are insufficient entries in the routing cache.

pub fn set_broadcast(&self, on: bool) -> Result<()>

Sets the value of the SO_BROADCAST option for this socket.

When enabled, this socket is allowed to send packets to a broadcast address.

Examples

use mio::net::UdpSocket;

let broadcast_socket = UdpSocket::bind("127.0.0.1:0".parse()?)?;
if broadcast_socket.broadcast()? == false {
    broadcast_socket.set_broadcast(true)?;
}

assert_eq!(broadcast_socket.broadcast()?, true);

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

Gets the value of the SO_BROADCAST option for this socket.

For more information about this option, see set_broadcast.

Examples

use mio::net::UdpSocket;

let broadcast_socket = UdpSocket::bind("127.0.0.1:0".parse()?)?;
assert_eq!(broadcast_socket.broadcast()?, false);

pub fn set_multicast_loop_v4(&self, on: bool) -> Result<()>

Sets the value of the IP_MULTICAST_LOOP option for this socket.

If enabled, multicast packets will be looped back to the local socket. Note that this may not have any affect on IPv6 sockets.

pub fn multicast_loop_v4(&self) -> Result<bool>

Gets the value of the IP_MULTICAST_LOOP option for this socket.

For more information about this option, see set_multicast_loop_v4.

pub fn set_multicast_ttl_v4(&self, ttl: u32) -> Result<()>

Sets the value of the IP_MULTICAST_TTL option for this socket.

Indicates the time-to-live value of outgoing multicast packets for this socket. The default value is 1 which means that multicast packets don’t leave the local network unless explicitly requested.

Note that this may not have any affect on IPv6 sockets.

pub fn multicast_ttl_v4(&self) -> Result<u32>

Gets the value of the IP_MULTICAST_TTL option for this socket.

For more information about this option, see set_multicast_ttl_v4.

pub fn set_multicast_loop_v6(&self, on: bool) -> Result<()>

Sets the value of the IPV6_MULTICAST_LOOP option for this socket.

Controls whether this socket sees the multicast packets it sends itself. Note that this may not have any affect on IPv4 sockets.

pub fn multicast_loop_v6(&self) -> Result<bool>

Gets the value of the IPV6_MULTICAST_LOOP option for this socket.

For more information about this option, see set_multicast_loop_v6.

pub 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 mio::net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:0".parse()?)?;
if socket.ttl()? < 255 {
    socket.set_ttl(255)?;
}

assert_eq!(socket.ttl()?, 255);

pub 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 mio::net::UdpSocket;

let socket = UdpSocket::bind("127.0.0.1:0".parse()?)?;
socket.set_ttl(255)?;

assert_eq!(socket.ttl()?, 255);

pub fn join_multicast_v4( &self, multiaddr: &Ipv4Addr, interface: &Ipv4Addr, ) -> Result<()>

Executes an operation of the IP_ADD_MEMBERSHIP type.

This function specifies a new multicast group for this socket to join. The address must be a valid multicast address, and interface is the address of the local interface with which the system should join the multicast group. If it’s equal to INADDR_ANY then an appropriate interface is chosen by the system.

pub fn join_multicast_v6( &self, multiaddr: &Ipv6Addr, interface: u32, ) -> Result<()>

Executes an operation of the IPV6_ADD_MEMBERSHIP type.

This function specifies a new multicast group for this socket to join. The address must be a valid multicast address, and interface is the index of the interface to join/leave (or 0 to indicate any interface).

pub fn leave_multicast_v4( &self, multiaddr: &Ipv4Addr, interface: &Ipv4Addr, ) -> Result<()>

Executes an operation of the IP_DROP_MEMBERSHIP type.

For more information about this option, see join_multicast_v4.

pub fn leave_multicast_v6( &self, multiaddr: &Ipv6Addr, interface: u32, ) -> Result<()>

Executes an operation of the IPV6_DROP_MEMBERSHIP type.

For more information about this option, see join_multicast_v6.

pub fn only_v6(&self) -> Result<bool>

Get the value of the IPV6_V6ONLY option on this socket.

pub fn take_error(&self) -> Result<Option<Error>>

Get the value of the SO_ERROR option on this socket.

This will retrieve the stored error in the underlying socket, clearing the field in the process. This can be useful for checking errors between calls.

pub fn try_io<F, T>(&self, f: F) -> Result<T>

where F: FnOnce() -> Result<T>,

Execute an I/O operation ensuring that the socket receives more events if it hits a WouldBlock error.

Notes

This method is required to be called for all I/O operations to ensure the user will receive events once the socket is ready again after returning a WouldBlock error.

Examples

use std::io;
#[cfg(any(unix, target_os = "wasi"))]
use std::os::fd::AsRawFd;
#[cfg(windows)]
use std::os::windows::io::AsRawSocket;
use mio::net::UdpSocket;

let address = "127.0.0.1:8080".parse().unwrap();
let dgram = UdpSocket::bind(address)?;

// Wait until the dgram is readable...

// Read from the dgram using a direct libc call, of course the
// `io::Read` implementation would be easier to use.
let mut buf = [0; 512];
let n = dgram.try_io(|| {
    let buf_ptr = &mut buf as *mut _ as *mut _;
    #[cfg(unix)]
    let res = unsafe { libc::recv(dgram.as_raw_fd(), buf_ptr, buf.len(), 0) };
    #[cfg(windows)]
    let res = unsafe { libc::recvfrom(dgram.as_raw_socket() as usize, buf_ptr, buf.len() as i32, 0, std::ptr::null_mut(), std::ptr::null_mut()) };
    if res != -1 {
        Ok(res as usize)
    } else {
        // If EAGAIN or EWOULDBLOCK is set by libc::recv, the closure
        // should return `WouldBlock` error.
        Err(io::Error::last_os_error())
    }
})?;
eprintln!("read {} bytes", n);

Trait Implementations

impl AsFd for UdpSocket

fn as_fd(&self) -> BorrowedFd<'_>

Borrows the file descriptor.

impl AsRawFd for UdpSocket

fn as_raw_fd(&self) -> RawFd

Extracts the raw file descriptor.

impl Debug for UdpSocket

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

Formats the value using the given formatter.

impl From<UdpSocket> for UdpSocket

fn from(socket: UdpSocket) -> Self

Converts to this type from the input type.

impl FromRawFd for UdpSocket

unsafe fn from_raw_fd(fd: RawFd) -> UdpSocket

Converts a RawFd to a UdpSocket.

Notes

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

impl IntoRawFd for UdpSocket

fn into_raw_fd(self) -> RawFd

Consumes this object, returning the raw underlying file descriptor.

impl Source for UdpSocket

fn register( &mut self, registry: &Registry, token: Token, interests: Interest, ) -> Result<()>

Register self with the given Registry instance.

fn reregister( &mut self, registry: &Registry, token: Token, interests: Interest, ) -> Result<()>

Re-register self with the given Registry instance.

fn deregister(&mut self, registry: &Registry) -> Result<()>

Deregister self from the given Registry instance.