groestlcoin / eclair

A scala implementation of the Lightning Network.

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

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

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

🚨 If you run Eclair on mainnet (which is the default setting):

  • Keep in mind that it is beta-quality software and don't put too much money in it
  • Eclair's JSON API should NOT be accessible from the outside world (similarly to Groestlcoin Core API)

Lightning Network Specification Compliance

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


Eclair Demo


Eclair offers a feature rich HTTP API that enables application developers to easily integrate.

For more information please visit the API documentation website.


Please visit our wiki to find detailed instructions on how to configure your node, connect to other nodes, open channels, send and receive payments and more advanced scenario.

You will find detailed guides and frequently asked questions there.


Configuring Groestlcoin Core

⚠️ Eclair requires Groestlcoin Core 2.17.1 or higher. If you are upgrading an existing wallet, you need to create a new address and send all your funds to that address.

Eclair needs a synchronized, segwit-ready, zeromq-enabled, wallet-enabled, non-pruning, tx-indexing Groestlcoin Core node. Eclair will use any GRS it finds in the Groestlcoin Core wallet to fund any channels you choose to open. Eclair will return GRS from closed channels to this wallet. You can configure your Groestlcoin Node to use either p2sh-segwit addresses or bech32 addresses, Eclair is compatible with both modes. If your Groestlcoin Core wallet has "non-segwit UTXOs" (outputs that are neither p2sh-segwit or bech32), you must send them to a p2sh-segwit or bech32 address.

Run groestlcoind with the following minimal groestlcoin.conf:


Installing Eclair

Eclair is developed in Scala, a powerful functional language that runs on the JVM, and is packaged as a JAR (Java Archive) file. We provide 2 different packages, which internally use the same core libraries:

  • eclair-node, which is a headless application that you can run on servers and desktops, and control from the command line
  • eclair-node-gui, which also includes a JavaFX GUI

To run Eclair, you first need to install Java, we recommend that you use OpenJDK 11. Other runtimes also work but we don't recommend using them.

Then download our latest release 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:


Here are some of the most common options:

name description default value
eclair.chain Which blockchain to use: regtest, testnet or mainnet mainnet
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 Groestlcoin Core RPC user foo
eclair.bitcoind.rpcpassword Groestlcoin Core RPC password bar
eclair.bitcoind.zmqblock Groestlcoin Core ZMQ block address "tcp://"
eclair.bitcoind.zmqtx Groestlcoin Core ZMQ tx address "tcp://"
eclair.gui.unit Unit in which amounts are displayed (possible values: msat, sat, bits, 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


Eclair uses logback for logging. To use a different configuration, and override the internal logback.xml, run:

java -Dlogback.configurationFile=/path/to/logback-custom.xml -jar eclair-node-gui-<version>-<commit_id>.jar


The files that you need to backup are located in your data directory. You must backup:

  • your seed (seed.dat)
  • your channel database (eclair.sqlite.bak under directory mainnet, testnet or regtest depending on which chain you're running on)

Your seed never changes once it has been created, but your channels will change whenever you receive or send payments. Eclair will create and maintain a snapshot of its database, named eclair.sqlite.bak, in your data directory, and update it when needed. This file is always consistent and safe to use even when Eclair is running, and this is what you should backup regularly.

For example you could configure a cron task for your backup job. Or you could configure an optional notification script to be called by eclair once a new database snapshot has been created, using the following option:

eclair.backup-notify-script = "/absolute/path/to/"

Make sure that your script is executable and uses an absolute path name for eclair.sqlite.bak.

Note that depending on your filesystem, in your backup process we recommend first moving eclair.sqlite.bak to some temporary file before copying that file to your final backup location.


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= -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

If you enabled the API you can check the status of eclair using the command line tool:

docker exec <container_name> eclair-cli -p foobar getinfo


For advanced usage, Eclair supports plugins written in Scala, Java, or any JVM-compatible language.

A valid plugin is a jar that contains an implementation of the Plugin interface.

Here is how to run Eclair with plugins:

java -jar eclair-node-<version>-<commit_id>.jar <plugin1.jar> <plugin2.jar> <...>

Testnet usage

Eclair is configured to run on mainnet by default, but you can still run it on testnet (or regtest): start your Groestlcoin Node in testnet mode (add testnet=1 in groestlcoin.conf or start with -testnet), and change Eclair's chain parameter and Groestlcoin RPC port:


You may also want to take advantage of the new configuration sections in groestlcoin.conf to manage parameters that are network specific, so you can easily run your groestlcoin node on both mainnet and testnet. For example you could use: