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0.2.1 Oct 6, 2020
0.2.0 Sep 29, 2020
0.1.0 Sep 28, 2020

#85 in Unix APIs

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Used in fizyr-rpc


803 lines


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().

Passing file descriptors and other ancillary data.

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.

&self versus &mut self

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. As such, you might except the socket to allow sending and receiving from a shared reference.

However, the tokio runtime only supports a single read task and a single write task waiting for readiness events. For that reason, you can only send and receive messages through an exclusive reference.

You can split the socket into a read and write half using UnixSeqpacket::split().


use tokio_seqpacket::UnixSeqpacket;

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

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


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