rust-libp2p/ping

Handles the /ipfs/ping/1.0.0 protocol. This allows pinging a remote node and waiting for an answer.

Usage

Create a Ping struct, which implements the ConnectionUpgrade trait. When used as a connection upgrade, it will produce a tuple of type (Pinger, impl Future<Item = ()>) which are named the pinger and the ponger.

The pinger has a method named ping which will send a ping to the remote, while the ponger is a future that will process the data received on the socket and will be signalled only when the connection closes.

About timeouts

For technical reasons, this crate doesn't handle timeouts. The action of pinging returns a future that is signalled only when the remote answers. If the remote is not responsive, the future will never be signalled.

For implementation reasons, resources allocated for a ping are only ever fully reclaimed after a pong has been received by the remote. Therefore if you repeatedly ping a non-responsive remote you will end up using more and more memory (albeit the amount is very very small every time), even if you destroy the future returned by ping.

This is probably not a problem in practice, because the nature of the ping protocol is to determine whether a remote is still alive, and any reasonable user of this crate will close connections to non-responsive remotes (which would then de-allocate memory for the ping).

Example

extern crate futures;
extern crate libp2p_ping;
extern crate libp2p_core;
extern crate libp2p_tcp_transport;
extern crate tokio_current_thread;

use futures::Future;
use libp2p_ping::Ping;
use libp2p_core::Transport;

let ping_finished_future = libp2p_tcp_transport::TcpConfig::new()
    .with_upgrade(Ping)
    .dial("127.0.0.1:12345".parse::<libp2p_core::Multiaddr>().unwrap()).unwrap_or_else(|_| panic!())
    .and_then(|((mut pinger, service), _)| {
        pinger.ping().map_err(|_| panic!()).select(service).map_err(|_| panic!())
    });

// Runs until the ping arrives.
tokio_current_thread::block_on_all(ping_finished_future).unwrap();