Getting started: your lab and your first payment

In the book, Alice buys a coffee from Bob's café with a phone wallet. Here you play every part. Your lab has four nodes on regtest: Alice and Dina run LND, Bob and Chan run c-lightning, and they are already linked in a line, Alice → Bob → Chan → Dina.

Step 1: Start the lab

In a terminal (on Windows, inside WSL2):

git clone https://github.com/comwanga/bitsacco-jifunze
cd bitsacco-jifunze/lab
./lab doctor     # checks Docker, memory, disk and port 7777
./lab up         # starts the nodes; the first run downloads about 2 GB

./lab up ends by printing a pairing code like ABCD-EFGH-JKLM. Paste it into the lab bar at the top of this page and press Connect. You should see six green chips: bitcoind and the four nodes.

Step 2: Dina asks to be paid

An invoice is a payment request. Dina makes one for 50,000 sats:

⚡Dina creates an invoice

CLI

NodeAlice · LNDBob · c-lightningChan · c-lightningDina · LNDNo node

# Dina sells coffee. She asks for 50,000 sats. lncli addinvoice --amt 50000 --memo "kahawa"

▶ RunCheckReset lessonRestore starter code

These exercises need a laptop with the lab running. You can read the lesson on your phone.

Look at the output: payment_request is the invoice text (it starts with lnbcrt, for Lightning on regtest), and r_hash is the hash of a secret only Dina knows.

Step 3: Alice pays

Copy Dina's payment_request into the next exercise, replacing INVOICE, and run it. The --force flag skips the "are you sure?" question.

⚡Alice pays Dina's invoice

CLI

NodeAlice · LNDBob · c-lightningChan · c-lightningDina · LNDNo node

# Paste Dina's payment_request (it starts with lnbcrt) in place of INVOICE. lncli payinvoice --force INVOICE

▶ RunCheckReset lessonRestore starter code

These exercises need a laptop with the lab running. You can read the lesson on your phone.

The table in the output shows the route: Alice → Bob → Chan → Dina, with a tiny fee for each hop. Payment status SUCCEEDED and a preimage mean Dina was paid: in lesson 8 you'll see why that secret is the receipt.

If something gets stuck, press Reset lesson on any exercise to restore this lesson's starting channels.