c-lightning: A specification compliant Lightning Network implementation in C
c-lightning is a standard compliant implementation of the Lightning Network protocol. The Lightning Network is a scalability solution for Bitcoin, enabling secure and instant transfer of funds between any two parties for any amount.
For more information about the Lightning Network please refer to http://lightning.network.
Project Status
This implementation is still very much a work in progress. It can be used for testing, but it should not be used for real funds. We do our best to identify and fix problems, and implement missing features.
Any help testing the implementation, reporting bugs, or helping with outstanding issues is very welcome. Don't hesitate to reach out to us on IRC at #lightning-dev @ freenode.net, #c-lightning @ freenode.net, or on the implementation-specific mailing list c-lightning@lists.ozlabs.org, or on the Lightning Network-wide mailing list lightning-dev@lists.linuxfoundation.org.
Getting Started
c-lightning currently only works on Linux (and possibly Mac OS with some
tweaking), and requires a locally (or remotely) running bitcoind
(version 0.15 or
above) that is fully caught up with the network you're testing on.
Pruning (prune=n option in bitcoin.conf) is not currently supported.
Installation
Please refer to the installation documentation for detailed instructions. For the impatient here's the gist of it for Ubuntu and Debian:
sudo apt-get update
sudo apt-get install -y \
autoconf automake build-essential git libtool libgmp-dev \
libsqlite3-dev python python3 net-tools zlib1g-dev libsodium-dev
git clone https://github.com/ElementsProject/lightning.git
cd lightning
./configure
make
Or if you like to throw docker
into the mix, you can use the official docker image either directly or as a base layer for more complex images.
The docker image is elementsproject/lightningd (from this Dockerfile).
Image tags with -dev
at the end are images built with DEVELOPER=1
.
If you build the image yourself, you can use the build arg DEVELOPER=1
to build c-lightning in developer mode.
It has the following environment variable:
EXPOSE_TCP
default to false, if true, use expose c-lightning RPC on port 9835. (Use this only for testing)
Here is an example of a docker-compose file with bitcoind and c-lightning on testnet
which expose bitcoind's RPC interface on default ports 18332
and c-lightning API on port 9735
:
version: "3"
services:
bitcoind:
image: nicolasdorier/docker-bitcoin:0.16.3
container_name: bitcoind
environment:
BITCOIN_EXTRA_ARGS: |
testnet=1
whitelist=0.0.0.0/0
server=1
rpcuser=rpcuser
rpcpassword=rpcpass
expose:
- "18332"
ports:
- "0.0.0.0:18333:18333"
volumes:
- "bitcoin_datadir:/data"
clightning_bitcoin:
image: elementsproject/lightningd
container_name: lightningd
command:
- --bitcoin-rpcconnect=bitcoind
- --bitcoin-rpcuser=rpcuser
- --bitcoin-rpcpassword=rpcpass
- --plugin-dir=/usr/libexec/c-lightning/plugins
- --network=testnet
- --alias=myawesomenode
- --log-level=debug
environment:
EXPOSE_TCP: "true"
expose:
- "9735"
ports:
- "0.0.0.0:9735:9735"
volumes:
- "clightning_bitcoin_datadir:/root/.lightning"
- "bitcoin_datadir:/etc/bitcoin"
links:
- bitcoind
volumes:
bitcoin_datadir:
clightning_bitcoin_datadir:
lightningd
Starting In order to start lightningd
you will need to have a local bitcoind
node running in either testnet or regtest mode:
bitcoind -daemon -testnet
Wait until bitcoind
has synchronized with the testnet network.
Make sure that you do not have walletbroadcast=0
in your
~/.bitcoin/bitcoin.conf
, or you may run into trouble.
Notice that currently pruned nodes are not supported and may result in
lightningd
being unable to synchronize with the blockchain.
You can start lightningd
with the following command:
lightningd/lightningd --network=testnet --log-level=debug
Listing all commands:
cli/lightning-cli help
will print a table of the API and lists the
following commands
Opening a channel on the Bitcoin testnet
First you need to transfer some funds to lightningd
so that it can
open a channel:
# Returns an address <address>
cli/lightning-cli newaddr
# Returns a transaction id <txid>
bitcoin-cli -testnet sendtoaddress <address> <amount_in_bitcoins>
lightningd
will register the funds once the transaction is confirmed.
You can obtain testcoins from a faucet such as coinfaucet.eu.
You can send them directly to the lightningd
address.
You may need to generate a p2sh-segwit address if the faucet does not support bech32:
# Return a p2sh-segwit address
cli/lightning-cli newaddr p2sh-segwit
Confirm lightningd
got funds by:
# Returns an array of on-chain funds.
cli/lightning-cli listfunds
Once lightningd
has funds, we can connect to a node and open a channel.
Let's assume the remote node is accepting connections at <ip>
(and optional <port>
, if not 9735) and has the node ID <node_id>
:
cli/lightning-cli connect <node_id> <ip> [<port>]
cli/lightning-cli fundchannel <node_id> <amount_in_satoshis>
This opens a connection and, on top of that connection, then opens
a channel.
The funding transaction needs 1 confirmation in order for the channel
to be usable, and 6 to be broadcast for others to use.
You can check the status of the channel using cli/lightning-cli listpeers
, which after 3 confirmations (1 on testnet) should say
that state
is CHANNELD_NORMAL
; after 6 confirmations you can use
cli/lightning-cli listchannels
to verify that the public
field is now
true
.
Different states
OPENINGD
means thatlightning_openingd
is negotiating channel opening.CHANNELD_AWAITING_LOCKIN
means thatlightning_channeld
is waiting until the minimum number of confirmation on the channel funding transaction.CHANNELD_NORMAL
means your channel is operating normally.CHANNELD_SHUTTING_DOWN
means one or both sides have asked to shut down the channel, and we're waiting for existing HTLCs to clear.CLOSINGD_SIGEXCHANGE
means we're trying to negotiate the fee for the mutual close transaction.CLOSINGD_COMPLETE
means we've broadcast our mutual close transaction (which spends the funding transaction) , but haven't seen it in a block yet.FUNDING_SPEND_SEEN
means we've seen the funding transaction spent.ONCHAIN
means that thelightning_onchaind
is tracking the onchain closing of the channel.AWAITING_UNILATERAL
means that we're waiting for a unilateral close to hit the blockchain.
All these states have more information about what's going on in the
status
field in listpeers
.
Sending and receiving payments
Payments in Lightning are invoice based.
The recipient creates an invoice with the expected <amount>
in
millisatoshi (or "any"
for a donation), a unique <label>
and a
<description>
the payer will see:
cli/lightning-cli invoice <amount> <label> <description>
This returns some internal details, and a standard invoice
string called bolt11
(named after the BOLT #11 lightning
spec).
The sender can feed this bolt11
string to the decodepay
command to
see what it is, and pay it simply using the pay
command:
cli/lightning-cli pay <bolt11>
Note that there are lower-level interfaces (and more options to these interfaces) for more sophisticated use.
Configuration File
lightningd can be configured either by passing options via the command line, or via a configuration file. Command line options will always override the values in the configuration file.
To use a configuration file, create a file named "config" within your ".lightning" directory. Usually, this will be ~/.lightning/config
Configuration options are set using a key=value pair on each line of the file, for example:
alias=SLEEPYDRAGON
rgb=008000
port=9735
network=testnet
For a full list of possible lightningd configuration options, run:
lightningd/lightningd --help
Further information
Developers
Developers wishing to contribute should start with the developer guide here.
JSON RPC
JSON-RPC interface is documented in the following manual pages:
For simple access to the JSON-RPC interface you can use the
cli/lightning-cli
tool, or the python API client.