Add support of ldk-node by randomlogin · Pull Request #307 · bitcoin-dev-project/sim-ln

randomlogin · 2026-04-08T13:13:25Z

This PR adds support of ldk-node to sim-ln.

Closes: #26

As ldk-node is not a daemon, before we start we parse the simulation config file and extract all ldk-nodes, build them and start. For that an additional chain source (bitcoind/esplora/electrum) is needed to start.

Before this PR can be merged, an update of used lighting libraries should be merged, as the current ldk-node has newer versions.

carlaKC · 2026-04-08T15:30:53Z

Before this PR can be merged, an update of used lighting libraries should be merged, as the current ldk-node has newer versions.

Feel free to bump this in a preparatory commit in this PR!

Add `LdkNode` as a new `LightningNode` implementation backed by ldk-server-client over gRPC-over-HTTPS. Supports keysend via `spontaneous_send`, payment tracking via polling `get_payment_details`, graph queries, and channel capacity reporting. Wire up `NodeConnection::Ldk` in sim-cli parsing so ldk-server nodes can be specified in sim.json alongside LND, CLN, and Eclair nodes. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

randomlogin · 2026-04-22T13:44:15Z

Initially I was trying to wire up ldk-node, which is not a daemon and I thought sim-ln could orchestrate ldk-node building, initialization. However it turned out that we want already running and funded nodes with opened channels, so this wasn't an option.

Added support of https://github.com/lightningdevkit/ldk-server, which is a reference daemon implementation with external API, it uses ldk-node internally.

Please note, that ldk-server has not yet been released, therefore a git reference and a revision is used in Cargo.toml

The configuration for ldk-server looks in the following way:

{
  "address": <ip:port or domain:port>,
  "api_key": <hex_encoded_api_key>,
  "cert": <path_to_tls_cert>,
  "network": <bitcoin|testnet|signet|regtest>
}

Please note that currently it's not possible to guess the network via RPC calls, that's why we need to provide it in the config. This might change in future.

carlaKC · 2026-04-22T14:21:58Z

Added support of https://github.com/lightningdevkit/ldk-server, which is a reference daemon implementation with external API, it uses ldk-node internally.
Please note, that ldk-server has not yet been released, therefore a git reference and a revision is used in Cargo.toml

Happy to go with server, I believe a release is coming soon ™️ !

carlaKC · 2026-04-27T13:39:14Z

Promise to get to review this week - sorry I've been a bit slow but it's on my list!

Previously we had to specify the network in the config file. Now, as the network field is added to the get-node-info response we can deduce it ourselves.

chuksys

Thanks for working on this! I've done a quick initial code/design review. It looks good so far, but I still need to run some local tests. I'll do that ASAP and get back to you with final feedback.

chuksys · 2026-05-11T15:28:09Z

 };

-pub struct LdkNode {
+pub struct LdkServer {


To align with the naming conventions of the other impls, let's go with LdkServerNode here & elsewhere. Sorry for the back-and-forth!

Renamed. Force pushed without a new commit.

chuksys · 2026-05-12T18:05:06Z

Just tested this using the following config:

{
    "nodes": [
      {
        "id": "alice",
        "address": "172.23.48.1:10002",
        "macaroon": "/mnt/c/Users/User/.polar/networks/1/volumes/lnd/alice/data/chain/bitcoin/regtest/admin.macaroon",
        "cert": "/mnt/c/Users/User/.polar/networks/1/volumes/lnd/alice/tls.cert"
      },
      {
        "id": "carol",
        "address": "172.23.48.1:10003",
        "macaroon": "/mnt/c/Users/User/.polar/networks/1/volumes/lnd/carol/data/chain/bitcoin/regtest/admin.macaroon",
        "cert": "/mnt/c/Users/User/.polar/networks/1/volumes/lnd/carol/tls.cert"      
      },
      {
        "address": "https://localhost:3536",
        "api_key": "b91adc35b0d407dab92f5b821d51e343a19497cadd0b7fd518b846c156db6df3",
        "cert": "/tmp/ldk-server/tls.crt"
      }
    ],
    "activity": [
      {
        "source": "alice",
        "destination": "carol",
        "interval_secs": 1,
        "amount_msat": 2000
      },
      {
        "source": "alice",
        "destination": "02df5ad45ae0bfc2b9fef546640ea89cd482274e92b7bb38e1d394822c8368d173",
        "interval_secs": 5,
        "amount_msat": 5000
      }
    ]
}

These are the logs:

chuksys · 2026-05-12T18:07:09Z

    Lnd(lnd::LndConnection),
    Cln(cln::ClnConnection),
    Eclair(eclair::EclairConnection),
+    Ldk(ldk_server::LdkServerConnection),


This should be LdkServer not Ldk.

chuksys · 2026-05-12T18:08:00Z

            NodeConnection::Lnd(c) => Arc::new(Mutex::new(LndNode::new(c).await?)),
            NodeConnection::Cln(c) => Arc::new(Mutex::new(ClnNode::new(c).await?)),
            NodeConnection::Eclair(c) => Arc::new(Mutex::new(EclairNode::new(c).await?)),
+            NodeConnection::Ldk(c) => Arc::new(Mutex::new(LdkServerNode::new(c).await?)),


This should be LdkServer not Ldk.

randomlogin force-pushed the add-ldk-support branch from b7eef3c to 8a6efb5 Compare April 15, 2026 16:00

randomlogin force-pushed the add-ldk-support branch from 83e2d28 to 526eb15 Compare April 22, 2026 13:29

update readme with ldk-server info

8d3e399

randomlogin marked this pull request as ready for review April 22, 2026 13:44

add ldk-server notes to readme

3a53974

randomlogin mentioned this pull request May 5, 2026

Support LDK server (daemon node) enigbe/sim-ln#1

Draft

2 tasks

Deduce ldk-server network via its API

d0a385e

Previously we had to specify the network in the config file. Now, as the network field is added to the get-node-info response we can deduce it ourselves.

chuksys reviewed May 11, 2026

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randomlogin requested a review from chuksys May 11, 2026 12:48

chuksys suggested changes May 11, 2026

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randomlogin force-pushed the add-ldk-support branch from 8337320 to 0c69012 Compare May 11, 2026 22:54

randomlogin requested a review from chuksys May 11, 2026 22:55

chuksys reviewed May 12, 2026

View reviewed changes

rename LdkNode to LdkServer

590d5ae

randomlogin force-pushed the add-ldk-support branch from 0c69012 to 590d5ae Compare May 12, 2026 18:19

randomlogin requested a review from chuksys May 12, 2026 18:20

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randomlogin commented Apr 8, 2026

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carlaKC commented Apr 8, 2026

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randomlogin commented Apr 22, 2026

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carlaKC commented Apr 22, 2026

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