Unix seqpacket sockets for tokio.

Seqpacket sockets combine a number of useful properties:

• They are connection oriented.
• They guarantee in-order message delivery.
• They provide datagrams with well-defined semantics for passing along file descriptors.

These properties make seqpacket sockets very well suited for local servers that need to pass file-descriptors around with their clients.

You can create a UnixSeqpacketListener to start accepting connections, or create a UnixSeqpacket to connect to a listening socket. You can also create a pair of connected sockets with UnixSeqpacket::pair().

You can use send_vectored_with_ancillary and recv_vectored_with_ancillary to send and receive ancillary data. This can be used to pass file descriptors and unix credentials over sockets.

Seqpacket sockets have well-defined semantics when sending or receiving on the same socket from different threads. Although the order is not guaranteed in that scenario, each datagram will be delivered intact. Since tokio 0.3, it is also possible for multiple tasks to await the same file descriptor. As such, all I/O functions now take &self instead of &mut self, and the split() API has been deprecated.

use tokio_seqpacket::UnixSeqpacket;

let mut socket = UnixSeqpacket::connect("/run/foo.sock").await?;
socket.send(b"Hello!").await?;

let mut buffer = [0u8; 128];
let len = socket.recv(&mut buffer).await?;
println!("{}", String::from_utf8_lossy(&buffer[..len]));