Learning-Bitcoin-from-the-Command-Line/13_4_Paying_a_Invoice.md

13.4: Paying a Invoice

ℹ️ NOTE: This is a draft in progress, so that I can get some feedback from early reviewers. It is not yet ready for learning.

📖 ***What is an invoice

Almost all payments made on the Lightning Network require an invoice, which is nothing more than a request for payment made by the recipient of the money and sent by different means to the user who will pay. The format for a Lightning invoice uses bech32 encoding, which is already used for Bitcoin Segregated Witness and all payment requests are single use.

Invoices have two parts:

• Human readable part: ln + (lnbc for Bitcoin mainnet, lntb for Bitcoin testnet, and lnbcrt for Bitcoin regtest) + data amount

• Data part : UNIX Timestamp + tagged parts include a payment hash, the pubkey of the payee node, an optional description of the payment, an expiration time, and some extra routing information.

Conside this ln invoice

lntb1m1p03ft7lpp5zve4dsgwgdxekqqq39vhgcnv6gfa2g2ktqy9lf0aph60d0388xmqdqqcqzpgsp545a9fphd8m5ayplcu8m5845cr4m0zcnyxddwv4g3zm32yprkfd4q9qy9qsq3s4y6cmyvh0qw9qm0sf80llxyyjy9xwrjds7lpkqhzv247jsm6q5me8t9e6ftquma664gz5u4a2rvs0yf4f0mlwtwfs6as5uj5djzhcqpnqlcj

This invoice starts with prefix ln+tb+1m that indicates milli, so you should multi by 0.001. That means we'll pay an invoice by 100000 satoshis.

Understanding your invoice

If you want to decode your lightning invoice you should use lightning-cli decodepay command that receives a string and checks and parses as specified by the BOLT 11 specification.

c$lightning-cli --network=testnet decodepay lntb1m1p03ft7lpp5zve4dsgwgdxekqqq39vhgcnv6gfa2g2ktqy9lf0aph60d0388xmqdqqcqzpgsp545a9fphd8m5ayplcu8m5845cr4m0zcnyxddwv4g3zm32yprkfd4q9qy9qsq3s4y6cmyvh0qw9qm0sf80llxyyjy9xwrjds7lpkqhzv247jsm6q5me8t9e6ftquma664gz5u4a2rvs0yf4f0mlwtwfs6as5uj5djzhcqpnqlcj
{
   "currency": "tb",
   "created_at": 1595191263,
   "expiry": 3600,
   "payee": "0302d48972ba7eef8b40696102ad114090fd4c146e381f18c7932a2a1d73566f84",
   "msatoshi": 100000000,
   "amount_msat": "100000000msat",
   "description": "First LN Payment - Learning Bitcoin and Lightning from the Command line.",
   "min_final_cltv_expiry": 40,
   "payment_secret": "ad3a5486ed3ee9d207f8e1f743d6981d76f16264335ae6551116e2a204764b6a",
   "features": "028200",
   "payment_hash": "133356c10e434d9b0000895974626cd213d5215658085fa5fd0df4f6be2739b6",
   "signature": "30450221008c2a4d636465de07141b7c1277ffe621244299c39361ef86c0b898aafa50de8102204de4eb2e7495839beeb5540a9caf543641e44d52fdfdcb7261aec29c951b215f"
}

Check your balance

As we did in previous chapter we have established an channel with a total capacity of 280.000 sats.

c$ lightning-cli --network=testnet listfunds
{
   "outputs": [
      {
         "txid": "9843c037f54a4660b297a9f2454e11d26d8659f084a284a5740bb15cb1d97aa6",
         "output": 0,
         "value": 19238,
         "amount_msat": "19238000msat",
         "scriptpubkey": "0014aa572371f29310cd677d039cdcd054156c1a9545",
         "address": "tb1q4ftjxu0jjvgv6emaqwwde5z5z4kp49299gmdpd",
         "status": "confirmed",
         "blockheight": 1780768,
         "reserved": false
      }
   ],
   "channels": [
      {
         "peer_id": "0302d48972ba7eef8b40696102ad114090fd4c146e381f18c7932a2a1d73566f84",
         "connected": true,
         "state": "CHANNELD_AWAITING_LOCKIN",
         "channel_sat": 280000,
         "our_amount_msat": "280000000msat",
         "channel_total_sat": **280000**,
         "amount_msat": "280000000msat",
         "funding_txid": "9843c037f54a4660b297a9f2454e11d26d8659f084a284a5740bb15cb1d97aa6",
         "funding_output": 1
      }
   ]
}

Paying your invoice

You should use lightning-cli pay command to pay the invoice. The pay RPC command attempts to find a route to the given destination, and send the funds asked in amount value.

c$lightning-cli --network=testnet pay 
lntb1m1p03ft7lpp5zve4dsgwgdxekqqq39vhgcnv6gfa2g2ktqy9lf0aph60d0388xmqdqqcqzpgsp545a9fphd8m5ayplcu8m5845cr4m0zcnyxddwv4g3zm32yprkfd4q9qy9qsq3s4y6cmyvh0qw9qm0sf80llxyyjy9xwrjds7lpkqhzv247jsm6q5me8t9e6ftquma664gz5u4a2rvs0yf4f0mlwtwfs6as5uj5djzhcqpnqlcj
{
   "id": 1,
   "payment_hash": "133356c10e434d9b0000895974626cd213d5215658085fa5fd0df4f6be2739b6",
   "destination": "0302d48972ba7eef8b40696102ad114090fd4c146e381f18c7932a2a1d73566f84",
   "msatoshi": 100000000,
   "amount_msat": "100000000msat",
   "msatoshi_sent": 100000000,
   "amount_sent_msat": "100000000msat",
   "created_at": 1595191379,
   "status": "complete",
   "payment_preimage": "8b7549ffd4e648374669d47992c1ab44086501d5dd85d7e3d15766d70e9196e3",
   "bolt11": "lntb1m1p03ft7lpp5zve4dsgwgdxekqqq39vhgcnv6gfa2g2ktqy9lf0aph60d0388xmqdqqcqzpgsp545a9fphd8m5ayplcu8m5845cr4m0zcnyxddwv4g3zm32yprkfd4q9qy9qsq3s4y6cmyvh0qw9qm0sf80llxyyjy9xwrjds7lpkqhzv247jsm6q5me8t9e6ftquma664gz5u4a2rvs0yf4f0mlwtwfs6as5uj5djzhcqpnqlcj"
}

Check your balance

We've performed payment successfully

c$ lightning-cli --network=testnet listfunds
{
   "outputs": [
      {
         "txid": "9843c037f54a4660b297a9f2454e11d26d8659f084a284a5740bb15cb1d97aa6",
         "output": 0,
         "value": 19238,
         "amount_msat": "19238000msat",
         "scriptpubkey": "0014aa572371f29310cd677d039cdcd054156c1a9545",
         "address": "tb1q4ftjxu0jjvgv6emaqwwde5z5z4kp49299gmdpd",
         "status": "confirmed",
         "blockheight": 1780768,
         "reserved": false
      }
   ],
   "channels": [
      {
         "peer_id": "0302d48972ba7eef8b40696102ad114090fd4c146e381f18c7932a2a1d73566f84",
         "connected": true,
         "state": "CHANNELD_NORMAL",
         "short_channel_id": "1780768x12x1",
         "channel_sat": 180000,
         "our_amount_msat": "180000000msat",
         "channel_total_sat": 280000,
         "amount_msat": "280000000msat",
         "funding_txid": "9843c037f54a4660b297a9f2454e11d26d8659f084a284a5740bb15cb1d97aa6",
         "funding_output": 1
      }
   ]
}