lightningd-rpc -- Lightning Daemon RPC Protocols

SYNOPSIS

~/.lightning/bitcoin/lightning-rpc

DESCRIPTION

lightningd(8) communicates via RPC, especially JSONRPC over the UNIX domain socket (by default $HOME/.lightning/bitcoin/lightning-rpc, but configuable with lightningd-config(5)).

JSON WIRE FORMAT

JSON RPC is defined at https://www.jsonrpc.org/specification and generally involves writing a JSON request with a unique ID, and receiving a response containing that ID.

Every response given by lightningd(8) is followed by two '\n' characters, which should not appear in normal JSON (though plugins may produce them). This means efficient code can simply read until it sees two '\n' characters, and then attempt to parse the JSON (if the JSON is incomplete, it should continue reading and file a bug).

JSON COMMANDS

We support "params" as an array (ordered parameters) or a dictionary (named parameters). In the array case, JSON "null" is treated as if the parameter was not specified (if that is allowed).

You should probably prefer named parameters if possible, as they have generally been shown to be less confusing for complex commands and more robust when fields are deprecated.

The lightning-cli(1) tool uses ordered parameters by default, but named parameters if explicitly specified or the first parameter contains an '='.

JSON IDS

JSON id fields in requests are used to match requests and responses. These used to be simple numbers, but with modern plugins that is deprecated: we use a specific format, which makes them very useful for debugging and tracking the cause of commands:

JSONID := IDPART ['/' IDPART]*
IDPART := PREFIX ':' METHOD '#' NUMBER

PREFIX is cln for the main daemon, cli for lightning-cli, and should be the plugin name for plugins. METHOD is an internal identifier, indicating what caused the request: for cli it's simply the method it's invoking, but for plugins it may be the routine which created the request. And NUMBER ensures uniqueness (it's usually a simple increment).

Importantly for plugins, incoming requests often trigger outgoing requests, and for these, the outgoing request id is created by appending a / and another id part into the incoming. This makes the chain of responsibility much clearer. e.g, this shows the JSON id of a sendrawtransaction RPC call, and we can tell that lightning-cli has invoked the withdraw command, which lightningd passes through to the txprepare plugin, which called sendrawtransaction.

cli:withdraw#123/cln:withdraw#7/txprepare:sendpsbt#1/cln:sendrawtransaction#9

JSON REPLIES

All JSON replies are wrapped in an object; this allows fields to be added in future. You should safely ignore any unknown fields.

Any field name which starts with "warning" is a specific warning, and should be documented in the commands' manual page. Each warning field has an associated human-readable string, but it's redudant, as each separate warning should have a distinct field name (e.g. warning_offer_unknown_currency and warning_offer_missing_description).

JSON TYPES

The exact specification for (most!) commands is specified in doc/schemas/ in the source directory. This is also used to generate part of the documentation for each command; the following types are referred to in addition to simple JSON types:

hex: an even-length string of hexidecimal digits.
hash: a 64-character hex which is a sha256 hash.
secret: a 64-character hex which is a secret of some kind.
u64: a JSON number without decimal point in the range 0 to 18446744073709551615 inclusive.
u32: a JSON number without decimal point in the range 0 to 4294967295 inclusive.
u16: a JSON number without decimal point in the range 0 to 65535 inclusive.
u16: a JSON number without decimal point in the range 0 to 255 inclusive.
pubkey: a 66-character hex which is an SEC-1 encoded secp256k1 point (usually used as a public key).
msat: a u64 which indicates an amount of millisatoshis. Deprecated: may also be a string of the number, with "msat" appended. As an input parameter, lightningd(8) will accept strings with suffixes (see below).
txid: a 64-character hex Bitcoin transaction identifier.
signature: a hex (144 bytes or less), which is a DER-encoded Bitcoin signature (without any sighash flags appended),
bip340sig: a 128-character hex which is a BIP-340 (Schnorr) signature.
point32: a 64-character hex which represents an x-only pubkey.
short_channel_id: a string of form BLOCK "x" TXNUM "x" OUTNUM.
short_channel_id_dir: a short_channel_id with "/0" or "/1" appended, indicating the direction between peers.
outpoint: a string containing a txid followed by a ":" and an output number (bitcoind uses this form).
feerate: an integer, or a string consisting of a number followed by "perkw" or "perkb".
outputdesc: an object containing onchain addresses as keys, and "all" or a valid msat field as values.

The following forms of msat are supported as parameters:

An integer (representing that many millisatoshis), e.g. 10000
A string of an integer N and the suffix msat (representing N millisatoshis) e.g. "10000msat"
A string of an integer N and the suffix sat (representing N times 1000 millisatoshis ) e.g. "10sat"
A string of a number N.M (where M is exactly three digits) and the suffix sat (representing N times 1000 plus M millisatoshis) e.g. "10.000sat"
A string of an integer N and the suffix btc (representing N times 100000000000 millisatoshis) e.g. "1btc"
A string of a number N.M (where M is exactly eight digits) and the suffix btc (representing N times 100000000000 plus M times 1000 millisatoshis) e.g "0.00000010btc"
A string of a number N.M (where M is exactly elevent digits) and the suffix btc (representing N times 100000000000 plus M millisatoshis) e.g "0.00000010000btc"

JSON NOTIFICATIONS

Notifications are (per JSONRPC spec) JSON commands without an "id" field. They give information about ongoing commands, but you need to enable them. See lightning-notifications(7).

FIELD FILTERING

You can restrict what fields are in the output of any command, by including a "filter" member in your request, alongside the standard "method" and "params" fields.

filter is a template, with keys indicating what fields are to be output (values must be true). Only fields which appear in the template will be output. For example, here is a normal result of listtransactions:

"result": {
  "transactions": [
    {
      "hash": "3b15dbc81d6a70abe1e75c1796c3eeba71c3954b7a90dfa67d55c1e989e20dbb",
      "rawtx": "020000000001019db609b099735fada240b82cec9da880b35d7a944065c280b8534cb4e2f5a7e90000000000feffffff0240420f000000000017a914d8b7ebd0ccc80266a97d9a828baf1877032ac6648731aff6290100000017a9142cb0814338091a73b388579b025c34f328dfb7898702473044022060a7ede98390111bc33bb12b09b38ad8e31b2a6fd62e9ce39a165b4c15ed39f8022040537219d42af28be18fd223af7cb2367f2300c9f0eb20dcaf677a96cd23efc7012102b2e79c36f2173bc24754214b6eeecd8dc753afda44f606d6f8c55c60c4d614ac65000000",
      "blockheight": 102,
      "txindex": 1,
      "locktime": 101,
      "version": 2,
      "inputs": [
        {
          "txid": "e9a7f5e2b44c53b880c26540947a5db380a89dec2cb840a2ad5f7399b009b69d",
          "index": 0,
          "sequence": 4294967294
        }
      ],
      "outputs": [
        {
          "index": 0,
          "amount_msat": "1000000000msat",
          "type": "deposit",
          "scriptPubKey": "a914d8b7ebd0ccc80266a97d9a828baf1877032ac66487"
        },
        {
          "index": 1,
          "amount_msat": "4998999857000msat",
          "scriptPubKey": "a9142cb0814338091a73b388579b025c34f328dfb78987"
        }
      ]
    },
    {
      "hash": "3a5ebaae466a9cb69c59553a3100ed545523e7450c32684cbc6bf0b305a6c448",
      "rawtx": "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",
      "blockheight": 103,
      "txindex": 1,
      "locktime": 102,
      "version": 2,
      "inputs": [
        {
          "txid": "3b15dbc81d6a70abe1e75c1796c3eeba71c3954b7a90dfa67d55c1e989e20dbb",
          "index": 0,
          "sequence": 4294967293
        }
      ],
      "outputs": [
        {
          "index": 0,
          "amount_msat": "894743000msat",
          "type": "deposit",
          "scriptPubKey": "0014c2ccab171c2a5be9dab52ec41b825863024c5466"
        },
        {
          "index": 1,
          "amount_msat": "100000000msat",
          "type": "channel_funding",
          "channel": "103x1x1",
          "scriptPubKey": "00205b8cd3b914cf67cdd8fa6273c930353dd36476734fbd962102c2df53b90880cd"
        }
      ]
    }
  ]
}

If we only wanted the output amounts and types, we would create a filter like so:

"filter": {"transactions": [{"outputs": [{"amount_msat": true, "type": true}]}]}

The result would be:

"result": {
  "transactions": [
    {
      "outputs": [
        {
          "amount_msat": "1000000000msat",
          "type": "deposit",
        },
        {
          "amount_msat": "4998999857000msat",
        }
      ]
    },
    {
      "outputs": [
        {
          "amount_msat": "894743000msat",
          "type": "deposit",
        },
        {
          "amount_msat": "100000000msat",
          "type": "channel_funding",
        }
      ]
    }
  ]
}

Note: "filter" doesn't change the order, just which fields are printed. Any fields not explictly mentioned are omitted from the output, but plugins which don't support filter (and some routines doing simple JSON transfers) may ignore "filter", so you should treat it as an optimazation only).

Note: if you specify an array where an object is specified or vice versa, the response may include a warning_parameter_filter field which describes the problem.

DEALING WITH FORMAT CHANGES

Fields can be added to the JSON output at any time, but to remove (or, very rarely) change a field requires a minimum deprecation period of 6 months and two releases. Usually a new field will be added if one is deprecated, so both will be present in transition.

To test that you're not using deprecated fields, you can use the lightningd-config(5) option allow-deprecated-apis=false. You should only use this in internal tests: it is not recommended that users use this directly.

The documentation tends to only refer to non-deprecated items, so if you seen an output field which is not documented, its either a bug (like that ever happens!) or a deprecated field you should ignore.

DEBUGGING

You can use log-level=io to see much of the JSON conversation (in hex) that occurs. It's extremely noisy though!

AUTHOR

Rusty Russell <rusty@rustcorp.com.au> wrote this man page, and much of the configuration language, but many others did the hard work of actually implementing these options.

RESOURCES

Main web site: https://github.com/ElementsProject/lightning

COPYING

Note: the modules in the ccan/ directory have their own licenses, but the rest of the code is covered by the BSD-style MIT license.