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 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-alpha10.

Configuring Bitcoin Core

Eclair needs a synchronized, segwit-ready, zeromq-enabled, wallet-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:

testnet=1
server=1
rpcuser=foo
rpcpassword=bar
txindex=1
zmqpubrawblock=tcp://127.0.0.1:29000
zmqpubrawtx=tcp://127.0.0.1:29000

# lines below only needed with Bitcoin Core 0.16+
deprecatedrpc=addwitnessaddress
addresstype=p2sh-segwit

Eclair will use any BTC it finds in the Bitcoin Core wallet to fund any channels you choose to open. Eclair will return BTC from closed channels to this wallet.

On testnet, the addresstype of all your UTXOs needs to be p2sh-of-p2wpkh. This is the default addresstype starting with Bitcoin Core 0.16, which provides native segwit support. For earlier versions of Bitcoin Core, additional steps are necessary.

• for new wallets created with Bitcoin Core 0.16 or later, no additional steps are necessary.
• for existing wallets migrated to Bitcoin Core 0.16 or later, you need to create a new address and send all your funds to that address.
• if you are running Bitcoin 0.15.1 or earlier, you need to create a segwit address manually. 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 available 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 ~/.eclair by default.

To change your node's configuration, create a file named eclair.conf in ~/.eclair. 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.enabled	Enable/disable the API	false. By default the API is disabled. If you want to enable it, you must set a password.
eclair.api.port	API HTTP port	8080
eclair.api.password	API password (BASIC)	"" (must be set if the API is enabled)
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"
eclair.gui.unit	Unit in which amounts are displayed (possible values: msat, sat, mbtc, btc)	btc

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	open a secure connection to a lightning node
connect	uri	open a secure connection to a lightning node
open	nodeId, fundingSatoshis, pushMsat = 0, feerateSatPerByte = ?, channelFlags = 0x01	open a channel with another lightning node, by default push = 0, feerate for the funding tx targets 6 blocks, and channel is announced
peers		list existing local peers
channels		list existing local channels
channels	nodeId	list existing local channels opened with a particular nodeId
channel	channelId	retrieve detailed information about a given channel
allnodes		list all known nodes
allchannels		list all known channels
allupdates		list all channels updates
allupdates	nodeId	list all channels updates for this nodeId
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
checkpayment	paymentHash	returns true if the payment has been received, false otherwise
checkpayment	paymentRequest	returns true if the payment has been received, false otherwise
close	channelId	close a channel
close	channelId, scriptPubKey	close a channel and send the funds to the given scriptPubKey
forceclose	channelId	force-close a channel by publishing the local commitment tx (careful: this is more expensive than a regular close and will incur a delay before funds are spendable)"
help		display available methods

Docker

A Dockerfile image is 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
• [3] Lightning Network Explorer - Explore testnet LN nodes you can connect to