Receiving Payments

To receive a payment, you'll need to create an invoice of your own with an amount and description. ChannelManager contains the remaining information needed for the invoice. Use the provided utility to generate an invoice and register a pending payment in ChannelManager.

• Rust
• Java

let amt_msat = 10_000;
let description = "coffee".to_string();
let invoice = match utils::create_invoice_from_channelmanager(
	&channel_manager,
	keys_manager,
	currency,
	Some(amt_msat),
	description,
).expect("ERROR: failed to create invoice");
let encoded_invoice = invoice.to_string();

String description = "coffee";
long amt_msat = 10_000L;
Result_InvoiceSignOrCreationErrorZ invoice = UtilMethods.invoice_from_channelmanager(
    channel_manager, keys_manager.as_KeysInterface(), LDKCurrency.LDKCurrency_Bitcoin,
	Option_u64Z.some(amt_msat), description);
assert invoice instanceof
    Result_InvoiceSignOrCreationErrorZ.Result_InvoiceSignOrCreationErrorZ_OK;
Invoice invoice = ((Result_InvoiceSignOrCreationErrorZ.Result_InvoiceSignOrCreationErrorZ_OK) invoice).res;
String encoded_invoice = invoice.to_str();

While it is possible to create an invoice without using the utility, ChannelManager will reject any incoming HTLCs for unregistered payments to protect your privacy. In this case, use either create_inbound_payment or create_inbound_payment_for_hash to register a payment with ChannelManager before creating the invoice with the returned payment hash and/or secret.

As with sending a payment, LDK will generate an event once a payment is received. It is your responsibility to handle the PaymentReceived event by using ChannelManager to release the preimage and claim the funds.

• Rust
• Java

// In the event handler passed to BackgroundProcessor::start
match event {
	Event::PaymentReceived { payment_hash, payment_preimage, payment_secret, amt, .. } => {
		let payment_hash = hex_utils::hex_str(&payment_hash.0);
		match channel_manager.claim_funds(payment_preimage.unwrap()) {
			true => println!("EVENT: received payment for {}", payment_hash),
			false => panic!("ERROR: failed to claim payment for {}", payment_hash),
		}
	}
	// ...
}

// In the `handle_event` method of ChannelManagerPersister implementation
else if (e instanceof Event.PaymentReceived) {
	// Handle successful payment
	Event.PaymentReceived event = ((Event.PaymentReceived) e);
	assert event.payment_preimage instanceof Option_PaymentPreimageZ;
	byte[] payment_preimage = ((Option_PaymentPreimageZ.Some) event.payment_preimage).some;
	assert channel_manager.claim_funds(payment_preimage);
}

So there you have it! Those are the basics of using LDK. As you can see, LDK offers a ton of flexibility for building Lightning-enabled wallets and apps.