Eclair (french for Lightning) is a scala implementation of the Lightning Network. It can run with or without a GUI, and a JSON-RPC API is also available.

This software follows the Lightning Network Specifications (BOLTs). Other implementations include lightning-c, lit, and lnd.

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🚧 Both the BOLTs and Eclair itself are a work in progress. Expect things to break/change!

⚠️ Eclair currently only runs on regtest or testnet. We recommend testing in regtest, as it allows you to generate blocks manually and not wait for confirmations.

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Lightning Network Specification Compliance

Eclair 0.2-alpha1 is compliant with the BOLTs at commit 06a5e6cbdbb4c6f8b8dab444de497cdb9c7d7f02, with the following caveats:

• BOLT 1: Base Protocol
• BOLT 2: Peer Protocol for Channel Management
• BOLT 3: Bitcoin Transaction and Script Formats
• BOLT 4: Onion Routing Protocol
• BOLT 5: Recommendations for On-chain Transaction Handling
  • If a revoked commitment tx is published, only the offender's main output will be stolen as punishment, not the HTLCs.
• BOLT 7: P2P Node and Channel Discovery
• BOLT 8: Encrypted and Authenticated Transport
• BOLT 9: Assigned Feature Flags

Overview

Installation

⚠️ Those are valid for the most up-to-date, unreleased, version of eclair. Here are the instructions for Eclair 0.2-alpha1.

Configuring Bitcoin Core

Eclair needs a synchronized, segwit-ready, zeromq-enabled, non-pruning, tx-indexing Bitcoin Core node. This means that on Windows you will need Bitcoin Core 0.14.0.

Run bitcoind with the following minimal bitcoin.conf:

regtest=1
server=1
rpcuser=XXX
rpcpassword=XXX
txindex=1
zmqpubrawblock=tcp://127.0.0.1:29000
zmqpubrawtx=tcp://127.0.0.1:29000

Installing Eclair

Windows

Just use the windows installer, it should create a shortcut on your desktop.

Linux, macOS or manual install on Windows

You need to first install java, more precisely a JRE 1.8.

⚠️ If you are using the OpenJDK JRE, you will need to build OpenJFX yourself, or run the application in --headless mode.

Then download the latest fat jar and run:

java -jar eclair-node_xxxxxx-fat.jar

Configuring Eclair

Command-line parameters

option	description	default value
--datadir	Path to the data directory	~/.eclair
--headless	Run Eclair without the GUI
--help, -h	Display usage text

⚠️ Using separate datadir is mandatory if you want to run several instances of eclair on the same machine. You will also have to change ports in the configuration (see below).

Configuration file

To change your node configuration, edit the file eclair.conf in datadir.

option	description	default value
eclair.server.port	TCP port	9735
eclair.api.port	HTTP port	8080
eclair.bitcoind.rpcuser	Bitcoin Core RPC user	foo
eclair.bitcoind.rpcpassword	Bitcoin Core RPC password	bar
eclair.bitcoind.zmq	Bitcoin Core ZMQ address	tcp://127.0.0.1:29000

→ see application.conf for full reference.

JSON-RPC API

method	params	description
connect	host, port, pubkey	connect to another lightning node through a secure connection
open	host, port, pubkey, fundingSatoshis, pushMsat	opens a channel with another lightning node
peers		list existing local peers
channels		list existing local channels
channel	channelId	retrieve detailed information about a given channel
network		list all nodes that have been announced
genh		generate a payment H
send	amountMsat, paymentHash, nodeId	send a payment to a lightning node
close	channelId	close a channel
close	channelId, scriptPubKey (optional)	close a channel and send the funds to the given scriptPubKey
help		display available methods

Resources

• [1] The Bitcoin Lightning Network: Scalable Off-Chain Instant Payments by Joseph Poon and Thaddeus Dryja
• [2] Reaching The Ground With Lightning by Rusty Russell