# Connect to Peers

In this section you'll learn how to join the lightning network.

Firstly we need to have the ability to do high performance I/O operations. LDK provides default implementations for initializing all of your networking needs. If you are using Rust, you can use our simple socket handling library lightning_net_tokio. In Kotlin/Java you can use the NioPeerHandler which uses Java's NIO I/O interface.

What it's used for: making peer connections, facilitating peer data to and from LDK

  • Rust
  • Kotlin
  • Swift 
use lightning_net_tokio; // use LDK's sample networking module

let listen_port = 9735;
let listener = tokio::net::TcpListener::bind(format!("0.0.0.0:{}", listen_port))
    .await.unwrap()
loop {
    let tcp_stream = listener.accept().await.unwrap().0;
    tokio::spawn(async move {
        // Use LDK's supplied networking battery to facilitate inbound
        // connections.
        lightning_net_tokio::setup_inbound(
            &peer_manager,
            tcp_stream.into_std().unwrap(),
        )
        .await;
    });
}

  
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Connections to other peers are established with PeerManager. You'll need to know the pubkey and address of another node that you want as a peer. Once the connection is established and the handshake is complete, PeerManager will show the peer's pubkey in its list of peers.

  • Rust
  • Kotlin
  • Swift 
match lightning_net_tokio::connect_outbound(Arc::clone(&peer_manager), pubkey, address).await {
	Some(connection_closed_future) => {
		let mut connection_closed_future = Box::pin(connection_closed_future);
		loop {
			// Make sure the connection is still established.
			match futures::poll!(&mut connection_closed_future) {
				std::task::Poll::Ready(_) => {
					panic!("ERROR: Peer disconnected before handshake completed");
				}
				std::task::Poll::Pending => {}
			}

			// Wait for the handshake to complete.
			match peer_manager.get_peer_node_ids().iter().find(|id| **id == pubkey) {
				Some(_) => break,
				None => tokio::time::sleep(std::time::Duration::from_millis(10)).await,
			}
		}
	}
	None => panic!("ERROR: Failed to connect to peer"),
}

  
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Dependencies: PeerManager

References: Rust lightning-net-tokio docs (opens new window), Rust PeerManager docs (opens new window), Java/Kotlin NioPeerHandler bindings (opens new window), Java/Kotlin PeerManager bindings (opens new window),

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