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.

🚨 We had reports of Eclair being tested on various segwit-enabled blockchains. Keep in mind that Eclair is still alpha quality software, by using it with actual coins you are putting your funds at risk!

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Lightning Network Specification Compliance

Please see the latest release note for detailed information on BOLT compliance.

Overview

Installation

⚠️ Those are valid for the most up-to-date, unreleased, version of eclair. Here are the instructions for Eclair 0.2-alpha5.

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+.

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

On testnet, you also need to make sure that all your UTXOs are p2sh-of-p2wpkh. To do this, use the debug console, create a new address with getnewaddress, import it as a witness address with addwitnessaddress, and send all your balance to this witness address. If you need to create and send funds manually, don't forget to create and specify a witness address for the change output (this option is avaliable on the GUI once you set the Enable coin control features wallet option).

Installing Eclair

The released binaries can be downloaded here.

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 (see below).

Then download the latest fat jar and depending on whether or not you want a GUI run the following command:

• with GUI:

java -jar eclair-node-gui-<version>-<commit_id>.jar

• without GUI:

java -jar eclair-node-<version>-<commit_id>.jar

Configuring Eclair

Configuration file

Eclair reads its configuration file, and write its logs, to a datadir directory, located in ~/.eclair by default.

To change your node's configuration, create a file named eclair.conf in datadir. Here's an example configuration file:

eclair.server.port=9735
eclair.node-alias=eclair
eclair.node-color=49daaa

Here are some of the most common options:

name	description	default value
eclair.server.port	Lightning TCP port	9735
eclair.api.port	API 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

Quotes are not required unless the value contains special characters. Full syntax guide here.

→ see reference.conf for full reference. There are many more options!

Java Environment Variables

Some advanced parameters can be changed with java environment variables. Most users won't need this and can skip this section.

⚠️ 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 eclair.conf (see above).

name	description	default value
eclair.datadir	Path to the data directory	~/.eclair
eclair.headless	Run eclair without a GUI
eclair.printToConsole	Log to stdout (in addition to eclair.log)

For example, to specify a different data directory you would run the following command:

java -Declair.datadir=/tmp/node1 -jar eclair-node-gui-<version>-<commit_id>.jar

JSON-RPC API

method	params	description
getinfo		return basic node information (id, chain hash, current block height)
connect	nodeId, host, port	connect to another lightning node through a secure connection
open	nodeId, host, port, 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
allnodes		list all known nodes
allchannels		list all known channels
receive	description	generate a payment request without a required amount (can be useful for donations)
receive	amountMsat, description	generate a payment request for a given amount
send	amountMsat, paymentHash, nodeId	send a payment to a lightning node
send	paymentRequest	send a payment to a lightning node using a BOLT11 payment request
send	paymentRequest, amountMsat	send a payment to a lightning node using a BOLT11 payment request and a custom amount
close	channelId	close a channel
close	channelId, scriptPubKey (optional)	close a channel and send the funds to the given scriptPubKey
help		display available methods

Docker

A Dockerfile images are built on each commit on docker hub for running a dockerized eclair-node.

You can use the JAVA_OPTS environment variable to set arguments to eclair-node.

docker run -ti --rm -e "JAVA_OPTS=-Xmx512m -Declair.api.binding-ip=0.0.0.0 -Declair.node-alias=node-pm -Declair.printToConsole" acinq\eclair

If you want to persist the data directory, you can make the volume to your host with the -v argument, as the following example:

docker run -ti --rm -v "/path_on_host:/data" -e "JAVA_OPTS=-Declair.printToConsole" acinq\eclair

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