std::net

Trait ToSocketAddrs

1.0.0 · source

pub trait ToSocketAddrs {
    type Iter: Iterator<Item = SocketAddr>;

    // Required method
    fn to_socket_addrs(&self) -> Result<Self::Iter>;
}

Expand description

A trait for objects which can be converted or resolved to one or more SocketAddr values.

This trait is used for generic address resolution when constructing network objects. By default it is implemented for the following types:

SocketAddr: to_socket_addrs is the identity function.
SocketAddrV4, SocketAddrV6, (IpAddr, u16), (Ipv4Addr, u16), (Ipv6Addr, u16): to_socket_addrs constructs a SocketAddr trivially.
(&str, u16): &str should be either a string representation of an IpAddr address as expected by FromStr implementation or a host name. u16 is the port number.
&str: the string should be either a string representation of a SocketAddr as expected by its FromStr implementation or a string like <host_name>:<port> pair where <port> is a u16 value.

This trait allows constructing network objects like TcpStream or UdpSocket easily with values of various types for the bind/connection address. It is needed because sometimes one type is more appropriate than the other: for simple uses a string like "localhost:12345" is much nicer than manual construction of the corresponding SocketAddr, but sometimes SocketAddr value is the main source of the address, and converting it to some other type (e.g., a string) just for it to be converted back to SocketAddr in constructor methods is pointless.

Addresses returned by the operating system that are not IP addresses are silently ignored.

§Examples

Creating a SocketAddr iterator that yields one item:

use std::net::{ToSocketAddrs, SocketAddr};

let addr = SocketAddr::from(([127, 0, 0, 1], 443));
let mut addrs_iter = addr.to_socket_addrs().unwrap();

assert_eq!(Some(addr), addrs_iter.next());
assert!(addrs_iter.next().is_none());

Creating a SocketAddr iterator from a hostname:

use std::net::{SocketAddr, ToSocketAddrs};

// assuming 'localhost' resolves to 127.0.0.1
let mut addrs_iter = "localhost:443".to_socket_addrs().unwrap();
assert_eq!(addrs_iter.next(), Some(SocketAddr::from(([127, 0, 0, 1], 443))));
assert!(addrs_iter.next().is_none());

// assuming 'foo' does not resolve
assert!("foo:443".to_socket_addrs().is_err());

Creating a SocketAddr iterator that yields multiple items:

use std::net::{SocketAddr, ToSocketAddrs};

let addr1 = SocketAddr::from(([0, 0, 0, 0], 80));
let addr2 = SocketAddr::from(([127, 0, 0, 1], 443));
let addrs = vec![addr1, addr2];

let mut addrs_iter = (&addrs[..]).to_socket_addrs().unwrap();

assert_eq!(Some(addr1), addrs_iter.next());
assert_eq!(Some(addr2), addrs_iter.next());
assert!(addrs_iter.next().is_none());

Attempting to create a SocketAddr iterator from an improperly formatted socket address &str (missing the port):

use std::io;
use std::net::ToSocketAddrs;

let err = "127.0.0.1".to_socket_addrs().unwrap_err();
assert_eq!(err.kind(), io::ErrorKind::InvalidInput);

TcpStream::connect is an example of an function that utilizes ToSocketAddrs as a trait bound on its parameter in order to accept different types:

use std::net::{TcpStream, Ipv4Addr};

let stream = TcpStream::connect(("127.0.0.1", 443));
// or
let stream = TcpStream::connect("127.0.0.1:443");
// or
let stream = TcpStream::connect((Ipv4Addr::new(127, 0, 0, 1), 443));