Fiber Cheat Code

A quick-reference cheat sheet for Fiber developers and node operators. Keep this page bookmarked for everyday operations.

Node Quick Start

Use Run a Fiber Node for installation and startup steps. This page focuses on command, RPC, and configuration quick references after a node is running.

export NO_PROXY=127.0.0.1,localhost

Common CLI Commands

Node & Peer

Channel

Invoice & Payment

RPC Quick Reference

The default RPC endpoint is http://127.0.0.1:8227. All calls use JSON-RPC 2.0.

Node & Peer

Channel

Invoice & Payment

Example RPC Call

curl -s -X POST -H "Content-Type: application/json" \
  -d '{"id": 42, "jsonrpc": "2.0", "method": "node_info", "params": []}' \
  http://127.0.0.1:8227

Channel Lifecycle

NegotiatingFunding -> CollaboratingFundingTx -> SigningCommitment
SigningCommitment -> AwaitingTxSignatures -> AwaitingChannelReady
AwaitingChannelReady -> ChannelReady -> ShuttingDown -> Closed

Payment Lifecycle

Created ──▶ Inflight ──┬──▶ Success
                       └──▶ Failed

Fiber uses a two-level state machine: a high-level PaymentSession represents the intent, and one or more PaymentAttempts handle actual routing. An attempt can move through Created, Inflight, Retrying, Success, and Failed.

Fee Calculation

The forwarding fee for a TLC (Timelock Contract) is calculated as:

fee = ⌈(amount × tlc_fee_proportional_millionths) / 1,000,000⌉

Example: With tlc_fee_proportional_millionths = 1000 (0.1%), forwarding 1,000 CKB earns the relay node 1 CKB.

Important Constants & Parameters

Capacity Formula

For CKB channels, each side must reserve CKB for on-chain operations:

Available Balance = Funded Amount − 99 CKB

Example: Fund 499 CKB → 499 − 99 = 400 CKB available for off-chain payments.

Testnet Resources

Public Testnet Nodes

Common Patterns

Multi-Hop Routing

You don't need a direct channel to every peer. Fiber automatically discovers paths through intermediate relay nodes:

┌───────┐        ┌───────┐        ┌───────┐        ┌───────┐
│ nodeA │ ─────▶ │ node1 │ ─────▶ │ node2 │ ─────▶ │ nodeB │
│:8227  │        │public │        │public │        │:8237  │
└───────┘        └───────┘        └───────┘        └───────┘
  sender        relay node 1     relay node 2      receiver

Local nodes do not need a public IP — they connect through public relay nodes. See Multi-Hop Routing for full details.

Channel Rebalancing

When one side of a channel is depleted, rebalance by sending a payment back to yourself:

Automatic — use send_payment with allow_self_payment: true:

{
  "jsonrpc": "2.0",
  "method": "send_payment",
  "params": [{
    "target_pubkey": "<your_own_pubkey>",
    "amount": "0x5F5E100",
    "keysend": true,
    "allow_self_payment": true
  }],
  "id": 1
}

Manual — use build_router + send_payment_with_router for control over the exact path. See Channel Rebalancing for details.

Keysend Payments

Send a payment without an invoice by specifying the recipient's pubkey directly:

fnn-cli payment send_payment --target-pubkey <recipient_pubkey> --amount 100000000 --keysend true

Keysend is useful for spontaneous payments, tipping, and machine-to-machine transactions where the recipient cannot pre-generate an invoice. For CKB payments, the CLI amount is in shannons (100000000 = 1 CKB).

Further reading:

• Channel Lifecycle — detailed channel state transitions
• Payment Lifecycle — payment session and attempt states
• HTTP RPC Reference — full RPC API reference
• Network Resources — public nodes, faucets, and explorers
• Channel Rebalancing — liquidity management