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    use fmt;
    use io::{self, Error, ErrorKind};
    use net::{ToSocketAddrs, SocketAddr, Ipv4Addr, Ipv6Addr};
    use sys_common::net as net_imp;
    use sys_common::{AsInner, FromInner, IntoInner};
    use time::Duration;

    /// A UDP socket.
    ///
    /// After creating a `UdpSocket` by [`bind`]ing it to a socket address, data can be
    /// [sent to] and [received from] any other socket address.
    ///
    /// Although UDP is a connectionless protocol, this implementation provides an interface
    /// to set an address where data should be sent and received from. After setting a remote
    /// address with [`connect`], data can be sent to and received from that address with
    /// [`send`] and [`recv`].
    ///
    /// As stated in the User Datagram Protocol's specification in [IETF RFC 768], UDP is
    /// an unordered, unreliable protocol; refer to [`TcpListener`] and [`TcpStream`] for TCP
    /// primitives.
    ///
    /// [`bind`]: #method.bind
    /// [`connect`]: #method.connect
    /// [IETF RFC 768]: https://tools.ietf.org/html/rfc768
    /// [`recv`]: #method.recv
    /// [received from]: #method.recv_from
    /// [`send`]: #method.send
    /// [sent to]: #method.send_to
    /// [`TcpListener`]: ../../std/net/struct.TcpListener.html
    /// [`TcpStream`]: ../../std/net/struct.TcpStream.html
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use std::net::UdpSocket;
    ///
    /// fn main() -> std::io::Result<()> {
    ///     {
    ///         let mut socket = UdpSocket::bind("127.0.0.1:34254")?;
    ///
    ///         // Receives a single datagram message on the socket. If `buf` is too small to hold
    ///         // the message, it will be cut off.
    ///         let mut buf = [0; 10];
    ///         let (amt, src) = socket.recv_from(&mut buf)?;
    ///
    ///         // Redeclare `buf` as slice of the received data and send reverse data back to origin.
    ///         let buf = &mut buf[..amt];
    ///         buf.reverse();
    ///         socket.send_to(buf, &src)?;
    ///     } // the socket is closed here
    ///     Ok(())
    /// }
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct UdpSocket(net_imp::UdpSocket);

    impl UdpSocket {
        /// Creates a UDP socket from the given address.
        ///
        /// The address type can be any implementor of [`ToSocketAddrs`] trait. See
        /// its documentation for concrete examples.
        ///
        /// If `addr` yields multiple addresses, `bind` will be attempted with
        /// each of the addresses until one succeeds and returns the socket. If none
        /// of the addresses succeed in creating a socket, the error returned from
        /// the last attempt (the last address) is returned.
        ///
        /// [`ToSocketAddrs`]: ../../std/net/trait.ToSocketAddrs.html
        ///
        /// # Examples
        ///
        /// Create a UDP socket bound to `127.0.0.1:3400`:
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:3400").expect("couldn't bind to address");
        /// ```
        ///
        /// Create a UDP socket bound to `127.0.0.1:3400`. If the socket cannot be
        /// bound to that address, create a UDP socket bound to `127.0.0.1:3401`:
        ///
        /// ```no_run
        /// use std::net::{SocketAddr, UdpSocket};
        ///
        /// let addrs = [
        ///     SocketAddr::from(([127, 0, 0, 1], 3400)),
        ///     SocketAddr::from(([127, 0, 0, 1], 3401)),
        /// ];
        /// let socket = UdpSocket::bind(&addrs[..]).expect("couldn't bind to address");
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<UdpSocket> {
            super::each_addr(addr, net_imp::UdpSocket::bind).map(UdpSocket)
        }

        /// Receives a single datagram message on the socket. On success, returns the number
        /// of bytes read and the origin.
        ///
        /// 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.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// let mut buf = [0; 10];
        /// let (number_of_bytes, src_addr) = socket.recv_from(&mut buf)
        ///                                         .expect("Didn't receive data");
        /// let filled_buf = &mut buf[..number_of_bytes];
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
            self.0.recv_from(buf)
        }

        /// Receives a single datagram message on the socket, without removing it from the
        /// queue. On success, returns the number of bytes read and the origin.
        ///
        /// 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.
        ///
        /// Successive calls return the same data. This is accomplished by passing
        /// `MSG_PEEK` as a flag to the underlying `recvfrom` system call.
        ///
        /// Do not use this function to implement busy waiting, instead use `libc::poll` to
        /// synchronize IO events on one or more sockets.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// let mut buf = [0; 10];
        /// let (number_of_bytes, src_addr) = socket.peek_from(&mut buf)
        ///                                         .expect("Didn't receive data");
        /// let filled_buf = &mut buf[..number_of_bytes];
        /// ```
        #[stable(feature = "peek", since = "1.18.0")]
        pub fn peek_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
            self.0.peek_from(buf)
        }

        /// 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.
        ///
        /// It is possible for `addr` to yield multiple addresses, but `send_to`
        /// will only send data to the first address yielded by `addr`.
        ///
        /// This will return an error when the IP version of the local socket
        /// does not match that returned from [`ToSocketAddrs`].
        ///
        /// See <https://github.com/rust-lang/rust/issues/34202> for more details.
        ///
        /// [`ToSocketAddrs`]: ../../std/net/trait.ToSocketAddrs.html
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.send_to(&[0; 10], "127.0.0.1:4242").expect("couldn't send data");
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn send_to<A: ToSocketAddrs>(&self, buf: &[u8], addr: A)
                                         -> io::Result<usize> {
            match addr.to_socket_addrs()?.next() {
                Some(addr) => self.0.send_to(buf, &addr),
                None => Err(Error::new(ErrorKind::InvalidInput,
                                       "no addresses to send data to")),
            }
        }

        /// Returns the socket address that this socket was created from.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::{Ipv4Addr, SocketAddr, SocketAddrV4, UdpSocket};
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// assert_eq!(socket.local_addr().unwrap(),
        ///            SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 34254)));
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn local_addr(&self) -> io::Result<SocketAddr> {
            self.0.socket_addr()
        }

        /// Creates a new independently owned handle to the underlying socket.
        ///
        /// The returned `UdpSocket` is a reference to the same socket that this
        /// object references. Both handles will read and write the same port, and
        /// options set on one socket will be propagated to the other.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// let socket_clone = socket.try_clone().expect("couldn't clone the socket");
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn try_clone(&self) -> io::Result<UdpSocket> {
            self.0.duplicate().map(UdpSocket)
        }

        /// Sets the read timeout to the timeout specified.
        ///
        /// If the value specified is [`None`], then [`read`] calls will block
        /// indefinitely. An [`Err`] is returned if the zero [`Duration`] is
        /// passed to this method.
        ///
        /// # Platform-specific behavior
        ///
        /// Platforms may return a different error code whenever a read times out as
        /// a result of setting this option. For example Unix typically returns an
        /// error of the kind [`WouldBlock`], but Windows may return [`TimedOut`].
        ///
        /// [`None`]: ../../std/option/enum.Option.html#variant.None
        /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
        /// [`read`]: ../../std/io/trait.Read.html#tymethod.read
        /// [`Duration`]: ../../std/time/struct.Duration.html
        /// [`WouldBlock`]: ../../std/io/enum.ErrorKind.html#variant.WouldBlock
        /// [`TimedOut`]: ../../std/io/enum.ErrorKind.html#variant.TimedOut
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_read_timeout(None).expect("set_read_timeout call failed");
        /// ```
        ///
        /// An [`Err`] is returned if the zero [`Duration`] is passed to this
        /// method:
        ///
        /// ```no_run
        /// use std::io;
        /// use std::net::UdpSocket;
        /// use std::time::Duration;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").unwrap();
        /// let result = socket.set_read_timeout(Some(Duration::new(0, 0)));
        /// let err = result.unwrap_err();
        /// assert_eq!(err.kind(), io::ErrorKind::InvalidInput)
        /// ```
        #[stable(feature = "socket_timeout", since = "1.4.0")]
        pub fn set_read_timeout(&self, dur: Option<Duration>) -> io::Result<()> {
            self.0.set_read_timeout(dur)
        }

        /// Sets the write timeout to the timeout specified.
        ///
        /// If the value specified is [`None`], then [`write`] calls will block
        /// indefinitely. An [`Err`] is returned if the zero [`Duration`] is
        /// passed to this method.
        ///
        /// # Platform-specific behavior
        ///
        /// Platforms may return a different error code whenever a write times out
        /// as a result of setting this option. For example Unix typically returns
        /// an error of the kind [`WouldBlock`], but Windows may return [`TimedOut`].
        ///
        /// [`None`]: ../../std/option/enum.Option.html#variant.None
        /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
        /// [`write`]: ../../std/io/trait.Write.html#tymethod.write
        /// [`Duration`]: ../../std/time/struct.Duration.html
        /// [`WouldBlock`]: ../../std/io/enum.ErrorKind.html#variant.WouldBlock
        /// [`TimedOut`]: ../../std/io/enum.ErrorKind.html#variant.TimedOut
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_write_timeout(None).expect("set_write_timeout call failed");
        /// ```
        ///
        /// An [`Err`] is returned if the zero [`Duration`] is passed to this
        /// method:
        ///
        /// ```no_run
        /// use std::io;
        /// use std::net::UdpSocket;
        /// use std::time::Duration;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").unwrap();
        /// let result = socket.set_write_timeout(Some(Duration::new(0, 0)));
        /// let err = result.unwrap_err();
        /// assert_eq!(err.kind(), io::ErrorKind::InvalidInput)
        /// ```
        #[stable(feature = "socket_timeout", since = "1.4.0")]
        pub fn set_write_timeout(&self, dur: Option<Duration>) -> io::Result<()> {
            self.0.set_write_timeout(dur)
        }

        /// Returns the read timeout of this socket.
        ///
        /// If the timeout is [`None`], then [`read`] calls will block indefinitely.
        ///
        /// [`None`]: ../../std/option/enum.Option.html#variant.None
        /// [`read`]: ../../std/io/trait.Read.html#tymethod.read
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_read_timeout(None).expect("set_read_timeout call failed");
        /// assert_eq!(socket.read_timeout().unwrap(), None);
        /// ```
        #[stable(feature = "socket_timeout", since = "1.4.0")]
        pub fn read_timeout(&self) -> io::Result<Option<Duration>> {
            self.0.read_timeout()
        }

        /// Returns the write timeout of this socket.
        ///
        /// If the timeout is [`None`], then [`write`] calls will block indefinitely.
        ///
        /// [`None`]: ../../std/option/enum.Option.html#variant.None
        /// [`write`]: ../../std/io/trait.Write.html#tymethod.write
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_write_timeout(None).expect("set_write_timeout call failed");
        /// assert_eq!(socket.write_timeout().unwrap(), None);
        /// ```
        #[stable(feature = "socket_timeout", since = "1.4.0")]
        pub fn write_timeout(&self) -> io::Result<Option<Duration>> {
            self.0.write_timeout()
        }

        /// 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
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_broadcast(false).expect("set_broadcast call failed");
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn set_broadcast(&self, broadcast: bool) -> io::Result<()> {
            self.0.set_broadcast(broadcast)
        }

        /// Gets the value of the `SO_BROADCAST` option for this socket.
        ///
        /// For more information about this option, see
        /// [`set_broadcast`][link].
        ///
        /// [link]: #method.set_broadcast
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_broadcast(false).expect("set_broadcast call failed");
        /// assert_eq!(socket.broadcast().unwrap(), false);
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn broadcast(&self) -> io::Result<bool> {
            self.0.broadcast()
        }

        /// 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.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_multicast_loop_v4(false).expect("set_multicast_loop_v4 call failed");
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn set_multicast_loop_v4(&self, multicast_loop_v4: bool) -> io::Result<()> {
            self.0.set_multicast_loop_v4(multicast_loop_v4)
        }

        /// Gets the value of the `IP_MULTICAST_LOOP` option for this socket.
        ///
        /// For more information about this option, see
        /// [`set_multicast_loop_v4`][link].
        ///
        /// [link]: #method.set_multicast_loop_v4
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_multicast_loop_v4(false).expect("set_multicast_loop_v4 call failed");
        /// assert_eq!(socket.multicast_loop_v4().unwrap(), false);
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn multicast_loop_v4(&self) -> io::Result<bool> {
            self.0.multicast_loop_v4()
        }

        /// 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.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_multicast_ttl_v4(42).expect("set_multicast_ttl_v4 call failed");
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn set_multicast_ttl_v4(&self, multicast_ttl_v4: u32) -> io::Result<()> {
            self.0.set_multicast_ttl_v4(multicast_ttl_v4)
        }

        /// Gets the value of the `IP_MULTICAST_TTL` option for this socket.
        ///
        /// For more information about this option, see
        /// [`set_multicast_ttl_v4`][link].
        ///
        /// [link]: #method.set_multicast_ttl_v4
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_multicast_ttl_v4(42).expect("set_multicast_ttl_v4 call failed");
        /// assert_eq!(socket.multicast_ttl_v4().unwrap(), 42);
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn multicast_ttl_v4(&self) -> io::Result<u32> {
            self.0.multicast_ttl_v4()
        }

        /// 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.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_multicast_loop_v6(false).expect("set_multicast_loop_v6 call failed");
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn set_multicast_loop_v6(&self, multicast_loop_v6: bool) -> io::Result<()> {
            self.0.set_multicast_loop_v6(multicast_loop_v6)
        }

        /// Gets the value of the `IPV6_MULTICAST_LOOP` option for this socket.
        ///
        /// For more information about this option, see
        /// [`set_multicast_loop_v6`][link].
        ///
        /// [link]: #method.set_multicast_loop_v6
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_multicast_loop_v6(false).expect("set_multicast_loop_v6 call failed");
        /// assert_eq!(socket.multicast_loop_v6().unwrap(), false);
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn multicast_loop_v6(&self) -> io::Result<bool> {
            self.0.multicast_loop_v6()
        }

        /// 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
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_ttl(42).expect("set_ttl call failed");
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
            self.0.set_ttl(ttl)
        }

        /// Gets the value of the `IP_TTL` option for this socket.
        ///
        /// For more information about this option, see [`set_ttl`][link].
        ///
        /// [link]: #method.set_ttl
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.set_ttl(42).expect("set_ttl call failed");
        /// assert_eq!(socket.ttl().unwrap(), 42);
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn ttl(&self) -> io::Result<u32> {
            self.0.ttl()
        }

        /// 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.
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn join_multicast_v4(&self, multiaddr: &Ipv4Addr, interface: &Ipv4Addr) -> io::Result<()> {
            self.0.join_multicast_v4(multiaddr, interface)
        }

        /// 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).
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn join_multicast_v6(&self, multiaddr: &Ipv6Addr, interface: u32) -> io::Result<()> {
            self.0.join_multicast_v6(multiaddr, interface)
        }

        /// Executes an operation of the `IP_DROP_MEMBERSHIP` type.
        ///
        /// For more information about this option, see
        /// [`join_multicast_v4`][link].
        ///
        /// [link]: #method.join_multicast_v4
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn leave_multicast_v4(&self, multiaddr: &Ipv4Addr, interface: &Ipv4Addr) -> io::Result<()> {
            self.0.leave_multicast_v4(multiaddr, interface)
        }

        /// Executes an operation of the `IPV6_DROP_MEMBERSHIP` type.
        ///
        /// For more information about this option, see
        /// [`join_multicast_v6`][link].
        ///
        /// [link]: #method.join_multicast_v6
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn leave_multicast_v6(&self, multiaddr: &Ipv6Addr, interface: u32) -> io::Result<()> {
            self.0.leave_multicast_v6(multiaddr, interface)
        }

        /// 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.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// match socket.take_error() {
        ///     Ok(Some(error)) => println!("UdpSocket error: {:?}", error),
        ///     Ok(None) => println!("No error"),
        ///     Err(error) => println!("UdpSocket.take_error failed: {:?}", error),
        /// }
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn take_error(&self) -> io::Result<Option<io::Error>> {
            self.0.take_error()
        }

        /// Connects this UDP socket to a remote address, allowing the `send` and
        /// `recv` syscalls to be used to send data and also applies filters to only
        /// receive data from the specified address.
        ///
        /// If `addr` yields multiple addresses, `connect` will be attempted with
        /// each of the addresses until the underlying OS function returns no
        /// error. Note that usually, a successful `connect` call does not specify
        /// that there is a remote server listening on the port, rather, such an
        /// error would only be detected after the first send. If the OS returns an
        /// error for each of the specified addresses, the error returned from the
        /// last connection attempt (the last address) is returned.
        ///
        /// # Examples
        ///
        /// Create a UDP socket bound to `127.0.0.1:3400` and connect the socket to
        /// `127.0.0.1:8080`:
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:3400").expect("couldn't bind to address");
        /// socket.connect("127.0.0.1:8080").expect("connect function failed");
        /// ```
        ///
        /// Unlike in the TCP case, passing an array of addresses to the `connect`
        /// function of a UDP socket is not a useful thing to do: The OS will be
        /// unable to determine whether something is listening on the remote
        /// address without the application sending data.
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn connect<A: ToSocketAddrs>(&self, addr: A) -> io::Result<()> {
            super::each_addr(addr, |addr| self.0.connect(addr))
        }

        /// Sends data on the socket to the remote address to which it is connected.
        ///
        /// The [`connect`] method will connect this socket to a remote address. This
        /// method will fail if the socket is not connected.
        ///
        /// [`connect`]: #method.connect
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.connect("127.0.0.1:8080").expect("connect function failed");
        /// socket.send(&[0, 1, 2]).expect("couldn't send message");
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn send(&self, buf: &[u8]) -> io::Result<usize> {
            self.0.send(buf)
        }

        /// Receives a single datagram message on the socket from the remote address to
        /// which it is connected. On success, returns 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. This
        /// method will fail if the socket is not connected.
        ///
        /// [`connect`]: #method.connect
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.connect("127.0.0.1:8080").expect("connect function failed");
        /// let mut buf = [0; 10];
        /// match socket.recv(&mut buf) {
        ///     Ok(received) => println!("received {} bytes {:?}", received, &buf[..received]),
        ///     Err(e) => println!("recv function failed: {:?}", e),
        /// }
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn recv(&self, buf: &mut [u8]) -> io::Result<usize> {
            self.0.recv(buf)
        }

        /// Receives single datagram on the socket from the remote address to which it is
        /// connected, without removing the message from input queue. On success, returns
        /// the number of bytes peeked.
        ///
        /// 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.
        ///
        /// Successive calls return the same data. This is accomplished by passing
        /// `MSG_PEEK` as a flag to the underlying `recv` system call.
        ///
        /// Do not use this function to implement busy waiting, instead use `libc::poll` to
        /// synchronize IO events on one or more sockets.
        ///
        /// The [`connect`] method will connect this socket to a remote address. This
        /// method will fail if the socket is not connected.
        ///
        /// [`connect`]: #method.connect
        ///
        /// # Errors
        ///
        /// This method will fail if the socket is not connected. The `connect` method
        /// will connect this socket to a remote address.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
        /// socket.connect("127.0.0.1:8080").expect("connect function failed");
        /// let mut buf = [0; 10];
        /// match socket.peek(&mut buf) {
        ///     Ok(received) => println!("received {} bytes", received),
        ///     Err(e) => println!("peek function failed: {:?}", e),
        /// }
        /// ```
        #[stable(feature = "peek", since = "1.18.0")]
        pub fn peek(&self, buf: &mut [u8]) -> io::Result<usize> {
            self.0.peek(buf)
        }

        /// Moves this UDP socket into or out of nonblocking mode.
        ///
        /// This will result in `recv`, `recv_from`, `send`, and `send_to`
        /// operations becoming nonblocking, i.e., immediately returning from their
        /// calls. If the IO operation is successful, `Ok` is returned and no
        /// further action is required. If the IO operation could not be completed
        /// and needs to be retried, an error with kind
        /// [`io::ErrorKind::WouldBlock`] is returned.
        ///
        /// On Unix platforms, calling this method corresponds to calling `fcntl`
        /// `FIONBIO`. On Windows calling this method corresponds to calling
        /// `ioctlsocket` `FIONBIO`.
        ///
        /// [`io::ErrorKind::WouldBlock`]: ../io/enum.ErrorKind.html#variant.WouldBlock
        ///
        /// # Examples
        ///
        /// Create a UDP socket bound to `127.0.0.1:7878` and read bytes in
        /// nonblocking mode:
        ///
        /// ```no_run
        /// use std::io;
        /// use std::net::UdpSocket;
        ///
        /// let socket = UdpSocket::bind("127.0.0.1:7878").unwrap();
        /// socket.set_nonblocking(true).unwrap();
        ///
        /// # fn wait_for_fd() { unimplemented!() }
        /// let mut buf = [0; 10];
        /// let (num_bytes_read, _) = loop {
        ///     match socket.recv_from(&mut buf) {
        ///         Ok(n) => break n,
        ///         Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
        ///             // wait until network socket is ready, typically implemented
        ///             // via platform-specific APIs such as epoll or IOCP
        ///             wait_for_fd();
        ///         }
        ///         Err(e) => panic!("encountered IO error: {}", e),
        ///     }
        /// };
        /// println!("bytes: {:?}", &buf[..num_bytes_read]);
        /// ```
        #[stable(feature = "net2_mutators", since = "1.9.0")]
        pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
            self.0.set_nonblocking(nonblocking)
        }
    }

    impl AsInner<net_imp::UdpSocket> for UdpSocket {
        fn as_inner(&self) -> &net_imp::UdpSocket { &self.0 }
    }

    impl FromInner<net_imp::UdpSocket> for UdpSocket {
        fn from_inner(inner: net_imp::UdpSocket) -> UdpSocket { UdpSocket(inner) }
    }

    impl IntoInner<net_imp::UdpSocket> for UdpSocket {
        fn into_inner(self) -> net_imp::UdpSocket { self.0 }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl fmt::Debug for UdpSocket {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            self.0.fmt(f)
        }
    }

    #[cfg(all(test, not(any(target_os = "cloudabi", target_os = "emscripten"))))]
    mod tests {
        use io::ErrorKind;
        use net::*;
        use net::test::{next_test_ip4, next_test_ip6};
        use sync::mpsc::channel;
        use sys_common::AsInner;
        use time::{Instant, Duration};
        use thread;

        fn each_ip(f: &mut dyn FnMut(SocketAddr, SocketAddr)) {
            f(next_test_ip4(), next_test_ip4());
            f(next_test_ip6(), next_test_ip6());
        }

        macro_rules! t {
            ($e:expr) => {
                match $e {
                    Ok(t) => t,
                    Err(e) => panic!("received error for `{}`: {}", stringify!($e), e),
                }
            }
        }

        #[test]
        fn bind_error() {
            match UdpSocket::bind("1.1.1.1:9999") {
                Ok(..) => panic!(),
                Err(e) => {
                    assert_eq!(e.kind(), ErrorKind::AddrNotAvailable)
                }
            }
        }

        #[test]
        fn socket_smoke_test_ip4() {
            each_ip(&mut |server_ip, client_ip| {
                let (tx1, rx1) = channel();
                let (tx2, rx2) = channel();

                let _t = thread::spawn(move|| {
                    let client = t!(UdpSocket::bind(&client_ip));
                    rx1.recv().unwrap();
                    t!(client.send_to(&[99], &server_ip));
                    tx2.send(()).unwrap();
                });

                let server = t!(UdpSocket::bind(&server_ip));
                tx1.send(()).unwrap();
                let mut buf = [0];
                let (nread, src) = t!(server.recv_from(&mut buf));
                assert_eq!(nread, 1);
                assert_eq!(buf[0], 99);
                assert_eq!(src, client_ip);
                rx2.recv().unwrap();
            })
        }

        #[test]
        fn socket_name_ip4() {
            each_ip(&mut |addr, _| {
                let server = t!(UdpSocket::bind(&addr));
                assert_eq!(addr, t!(server.local_addr()));
            })
        }

        #[test]
        fn udp_clone_smoke() {
            each_ip(&mut |addr1, addr2| {
                let sock1 = t!(UdpSocket::bind(&addr1));
                let sock2 = t!(UdpSocket::bind(&addr2));

                let _t = thread::spawn(move|| {
                    let mut buf = [0, 0];
                    assert_eq!(sock2.recv_from(&mut buf).unwrap(), (1, addr1));
                    assert_eq!(buf[0], 1);
                    t!(sock2.send_to(&[2], &addr1));
                });

                let sock3 = t!(sock1.try_clone());

                let (tx1, rx1) = channel();
                let (tx2, rx2) = channel();
                let _t = thread::spawn(move|| {
                    rx1.recv().unwrap();
                    t!(sock3.send_to(&[1], &addr2));
                    tx2.send(()).unwrap();
                });
                tx1.send(()).unwrap();
                let mut buf = [0, 0];
                assert_eq!(sock1.recv_from(&mut buf).unwrap(), (1, addr2));
                rx2.recv().unwrap();
            })
        }

        #[test]
        fn udp_clone_two_read() {
            each_ip(&mut |addr1, addr2| {
                let sock1 = t!(UdpSocket::bind(&addr1));
                let sock2 = t!(UdpSocket::bind(&addr2));
                let (tx1, rx) = channel();
                let tx2 = tx1.clone();

                let _t = thread::spawn(move|| {
                    t!(sock2.send_to(&[1], &addr1));
                    rx.recv().unwrap();
                    t!(sock2.send_to(&[2], &addr1));
                    rx.recv().unwrap();
                });

                let sock3 = t!(sock1.try_clone());

                let (done, rx) = channel();
                let _t = thread::spawn(move|| {
                    let mut buf = [0, 0];
                    t!(sock3.recv_from(&mut buf));
                    tx2.send(()).unwrap();
                    done.send(()).unwrap();
                });
                let mut buf = [0, 0];
                t!(sock1.recv_from(&mut buf));
                tx1.send(()).unwrap();

                rx.recv().unwrap();
            })
        }

        #[test]
        fn udp_clone_two_write() {
            each_ip(&mut |addr1, addr2| {
                let sock1 = t!(UdpSocket::bind(&addr1));
                let sock2 = t!(UdpSocket::bind(&addr2));

                let (tx, rx) = channel();
                let (serv_tx, serv_rx) = channel();

                let _t = thread::spawn(move|| {
                    let mut buf = [0, 1];
                    rx.recv().unwrap();
                    t!(sock2.recv_from(&mut buf));
                    serv_tx.send(()).unwrap();
                });

                let sock3 = t!(sock1.try_clone());

                let (done, rx) = channel();
                let tx2 = tx.clone();
                let _t = thread::spawn(move|| {
                    match sock3.send_to(&[1], &addr2) {
                        Ok(..) => { let _ = tx2.send(()); }
                        Err(..) => {}
                    }
                    done.send(()).unwrap();
                });
                match sock1.send_to(&[2], &addr2) {
                    Ok(..) => { let _ = tx.send(()); }
                    Err(..) => {}
                }
                drop(tx);

                rx.recv().unwrap();
                serv_rx.recv().unwrap();
            })
        }

        #[test]
        fn debug() {
            let name = if cfg!(windows) {"socket"} else {"fd"};
            let socket_addr = next_test_ip4();

            let udpsock = t!(UdpSocket::bind(&socket_addr));
            let udpsock_inner = udpsock.0.socket().as_inner();
            let compare = format!("UdpSocket {{ addr: {:?}, {}: {:?} }}",
                                  socket_addr, name, udpsock_inner);
            assert_eq!(format!("{:?}", udpsock), compare);
        }

        // FIXME: re-enabled bitrig/openbsd/netbsd tests once their socket timeout code
        //        no longer has rounding errors.
        #[cfg_attr(any(target_os = "bitrig", target_os = "netbsd", target_os = "openbsd"), ignore)]
        #[test]
        fn timeouts() {
            let addr = next_test_ip4();

            let stream = t!(UdpSocket::bind(&addr));
            let dur = Duration::new(15410, 0);

            assert_eq!(None, t!(stream.read_timeout()));

            t!(stream.set_read_timeout(Some(dur)));
            assert_eq!(Some(dur), t!(stream.read_timeout()));

            assert_eq!(None, t!(stream.write_timeout()));

            t!(stream.set_write_timeout(Some(dur)));
            assert_eq!(Some(dur), t!(stream.write_timeout()));

            t!(stream.set_read_timeout(None));
            assert_eq!(None, t!(stream.read_timeout()));

            t!(stream.set_write_timeout(None));
            assert_eq!(None, t!(stream.write_timeout()));
        }

        #[test]
        fn test_read_timeout() {
            let addr = next_test_ip4();

            let stream = t!(UdpSocket::bind(&addr));
            t!(stream.set_read_timeout(Some(Duration::from_millis(1000))));

            let mut buf = [0; 10];

            let start = Instant::now();
            loop {
                let kind = stream.recv_from(&mut buf).err().expect("expected error").kind();
                if kind != ErrorKind::Interrupted {
                    assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut,
                            "unexpected_error: {:?}", kind);
                    break;
                }
            }
            assert!(start.elapsed() > Duration::from_millis(400));
        }

        #[test]
        fn test_read_with_timeout() {
            let addr = next_test_ip4();

            let stream = t!(UdpSocket::bind(&addr));
            t!(stream.set_read_timeout(Some(Duration::from_millis(1000))));

            t!(stream.send_to(b"hello world", &addr));

            let mut buf = [0; 11];
            t!(stream.recv_from(&mut buf));
            assert_eq!(b"hello world", &buf[..]);

            let start = Instant::now();
            loop {
                let kind = stream.recv_from(&mut buf).err().expect("expected error").kind();
                if kind != ErrorKind::Interrupted {
                    assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut,
                            "unexpected_error: {:?}", kind);
                    break;
                }
            }
            assert!(start.elapsed() > Duration::from_millis(400));
        }

        // Ensure the `set_read_timeout` and `set_write_timeout` calls return errors
        // when passed zero Durations
        #[test]
        fn test_timeout_zero_duration() {
            let addr = next_test_ip4();

            let socket = t!(UdpSocket::bind(&addr));

            let result = socket.set_write_timeout(Some(Duration::new(0, 0)));
            let err = result.unwrap_err();
            assert_eq!(err.kind(), ErrorKind::InvalidInput);

            let result = socket.set_read_timeout(Some(Duration::new(0, 0)));
            let err = result.unwrap_err();
            assert_eq!(err.kind(), ErrorKind::InvalidInput);
        }

        #[test]
        fn connect_send_recv() {
            let addr = next_test_ip4();

            let socket = t!(UdpSocket::bind(&addr));
            t!(socket.connect(addr));

            t!(socket.send(b"hello world"));

            let mut buf = [0; 11];
            t!(socket.recv(&mut buf));
            assert_eq!(b"hello world", &buf[..]);
        }

        #[test]
        fn connect_send_peek_recv() {
            each_ip(&mut |addr, _| {
                let socket = t!(UdpSocket::bind(&addr));
                t!(socket.connect(addr));

                t!(socket.send(b"hello world"));

                for _ in 1..3 {
                    let mut buf = [0; 11];
                    let size = t!(socket.peek(&mut buf));
                    assert_eq!(b"hello world", &buf[..]);
                    assert_eq!(size, 11);
                }

                let mut buf = [0; 11];
                let size = t!(socket.recv(&mut buf));
                assert_eq!(b"hello world", &buf[..]);
                assert_eq!(size, 11);
            })
        }

        #[test]
        fn peek_from() {
            each_ip(&mut |addr, _| {
                let socket = t!(UdpSocket::bind(&addr));
                t!(socket.send_to(b"hello world", &addr));

                for _ in 1..3 {
                    let mut buf = [0; 11];
                    let (size, _) = t!(socket.peek_from(&mut buf));
                    assert_eq!(b"hello world", &buf[..]);
                    assert_eq!(size, 11);
                }

                let mut buf = [0; 11];
                let (size, _) = t!(socket.recv_from(&mut buf));
                assert_eq!(b"hello world", &buf[..]);
                assert_eq!(size, 11);
            })
        }

        #[test]
        fn ttl() {
            let ttl = 100;

            let addr = next_test_ip4();

            let stream = t!(UdpSocket::bind(&addr));

            t!(stream.set_ttl(ttl));
            assert_eq!(ttl, t!(stream.ttl()));
        }

        #[test]
        fn set_nonblocking() {
            each_ip(&mut |addr, _| {
                let socket = t!(UdpSocket::bind(&addr));

                t!(socket.set_nonblocking(true));
                t!(socket.set_nonblocking(false));

                t!(socket.connect(addr));

                t!(socket.set_nonblocking(false));
                t!(socket.set_nonblocking(true));

                let mut buf = [0];
                match socket.recv(&mut buf) {
                    Ok(_) => panic!("expected error"),
                    Err(ref e) if e.kind() == ErrorKind::WouldBlock => {}
                    Err(e) => panic!("unexpected error {}", e),
                }
            })
        }
    }

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