Connect Public Nodes

Overview

This document provides a user manual for connecting to the public Testnet nodes of the Fiber network. It covers running a local node, establishing a channel with a public node, and transferring CKB and RUSD(stablecoin) within the channels. If you haven't read the Run a Fiber Node guide and the Basic Transfer Example, it is highly recommended to read them first.

Testnet Public Nodes' Addresses

node1

"/ip4/18.162.235.225/tcp/8119/p2p/QmXen3eUHhywmutEzydCsW4hXBoeVmdET2FJvMX69XJ1Eo"

node2

"/ip4/18.163.221.211/tcp/8119/p2p/QmbKyzq9qUmymW2Gi8Zq7kKVpPiNA1XUJ6uMvsUC4F3p89"

Local Node Deployment

1. Download fnn

   Please visit the releases page to download and use the latest version of fnn (v0.8.0 or higher).

   mkdir tmp && cd tmp
   tar xzvf fnn-latest.tar.gz

   macOS Security

   If you're using macOS, the downloaded binary may be blocked by Gatekeeper. Remove the quarantine attribute:

   xattr -d com.apple.quarantine fnn fnn-cli fnn-migrate

2. Export the account private key to the fiber node's ckb directory

   Here, the ckb-cli is used to create an account, which will later be used to pay for opening channels between the local node and the public testnet node. If ckb-cli is not installed, please download it from the releases.

   # Create a local node directory named nodeA
   mkdir -p testnet-fnn/nodeA/ckb
   
   # Create a new CKB account (save the lock_arg output)
   ./ckb-cli account new
   
   # Export the private key (replace with your actual lock_arg)
   ./ckb-cli account export --lock-arg <YOUR_LOCK_ARG> --extended-privkey-path ./exported-key
   
   # Copy the key to the node directory (run from the same directory as ckb-cli)
   head -n 1 ./exported-key > testnet-fnn/nodeA/ckb/key
   chmod 600 testnet-fnn/nodeA/ckb/key
   
   # Verify the key was copied correctly
   ./ckb-cli util key-info --privkey-path testnet-fnn/nodeA/ckb/key

3. Copy config.yml and fnn-cli

   cp config/testnet/config.yml testnet-fnn/nodeA
   cp fnn-cli testnet-fnn/nodeA

   HTTP Proxy Issues

   If you encounter 503 Service Unavailable errors when using fnn-cli, it may be due to HTTP proxy settings. Set NO_PROXY to exclude local addresses:

   export NO_PROXY=127.0.0.1,localhost

4. Fund nodeA's address with 10000ckb and 20RUSD via faucet

   The RUSD faucet cannot directly fill an address, so you can first claim 20RUSD through a wallet like joyid, then transfer it to nodeA's address from the joyid wallet page.

   • ckb: https://faucet.nervos.org

   • RUSD: https://testnet0815.stablepp.xyz/faucet

5. Start the node A

   You need to set a FIBER_SECRET_KEY_PASSWORD environment variable in the startup command to encrypt your wallet private key file. I used 123 here for demo purposes, but I recommend using a strong password.

   FIBER_SECRET_KEY_PASSWORD='123' RUST_LOG=info ./fnn -c testnet-fnn/nodeA/config.yml -d testnet-fnn/nodeA > testnet-fnn/nodeA/a.log 2>&1 &

Establishing a CKB Channel with Public Node 1

1. Establish a network connection between nodeA and node1

   First, get node1's pubkey by connecting to its RPC endpoint:

   curl -s --location 'http://18.162.235.225:8227' --header 'Content-Type: application/json' --data '{
       "id": 1,
       "jsonrpc": "2.0",
       "method": "node_info"
   }' | grep -o '"pubkey":"[^"]*"'

   Then connect using the pubkey:

   Using CLI:

   cd testnet-fnn/nodeA && ./fnn-cli peer connect_peer --address "/ip4/18.162.235.225/tcp/8119/p2p/QmXen3eUHhywmutEzydCsW4hXBoeVmdET2FJvMX69XJ1Eo"

   HTTP Proxy Issues

   If you encounter 503 Service Unavailable or connection errors when using fnn-cli, it may be due to HTTP proxy settings on your system. Set NO_PROXY to exclude local addresses:

   export NO_PROXY=127.0.0.1,localhost

   Using RPC:

   curl -s --location 'http://127.0.0.1:8227' --header 'Content-Type: application/json' --data '{
       "id": 1,
       "jsonrpc": "2.0",
       "method": "connect_peer",
       "params": [
           {
               "pubkey": "<node1_pubkey>",
               "address": "/ip4/18.162.235.225/tcp/8119/p2p/QmXen3eUHhywmutEzydCsW4hXBoeVmdET2FJvMX69XJ1Eo"
           }
       ]
   }'

   {"jsonrpc":"2.0","result":null,"id":1}

2. Establish a channel with 500ckb: nodeA (500ckb) ⟺ node1 (250ckb)

   Node1 has open_channel_auto_accept_min_ckb_funding_amount set at 438ckb, so please input 500ckb or more.

   Using CLI:

   cd testnet-fnn/nodeA && ./fnn-cli channel open_channel \
     --pubkey <node1_pubkey> \
     --funding-amount 50000000000 \
     --public true

   Using RPC:

   curl -s --location 'http://127.0.0.1:8227' --header 'Content-Type: application/json' --data '{
       "id": 2,
       "jsonrpc": "2.0",
       "method": "open_channel",
       "params": [
           {
               "pubkey": "<node1_pubkey>",
               "funding_amount": "0xba43b7400",
               "public": true
           }
       ]
   }'

   {"jsonrpc":"2.0","result":{"temporary_channel_id":"0x30089ec4c8ce1e1d4930220c2bff856eec7ab44550e15b76d62489fd42eaafe8"},"id":2}

3. Query the channels between nodeA and node1

   Using CLI:

   ./fnn-cli channel list_channels

   Using RPC:

   curl -s --location 'http://127.0.0.1:8227' --header 'Content-Type: application/json' --data '{
       "id": 3,
       "jsonrpc": "2.0",
       "method": "list_channels",
       "params": [
           {
               "peer_pubkey": "<node1_pubkey>"
           }
       ]
   }'

   Wait until the state_name changes to ChannelReady.

   Note: When the channel has just changed to the ChannelReady state and you attempt to use send_payment, you may still encounter an error: Failed to build route. This is because the network graph (gossip protocol) has not fully synced yet, and your node doesn't know the routing paths to other nodes. It is advisable to wait for some time (usually a few minutes) before trying again.

   {"jsonrpc":"2.0","result":{"channels":[{"channel_id":"0x26ce85d57fb4a1a826cbf4862358862317a83b775090625550d8be12c6ce9569","is_public":true,"channel_outpoint":"0x9bb2a8a4bebaf793a235ba2ec87051ae0018b58736b6741df74009ca8101cb8d00000000","peer_pubkey":"<node1_pubkey>","funding_udt_type_script":null,"state":{"state_name":"CHANNEL_READY","state_flags":[]},"local_balance":"0xa32aef600","offered_tlc_balance":"0x0","remote_balance":"0x460913c00","received_tlc_balance":"0x0","latest_commitment_transaction_hash":"0x18ef541a5a195c0ea4715a7783964b3c4be8fba6bd25542e626f91ef1673e3e4","created_at":"0x195892d237f","enabled":true,"tlc_expiry_delta":"0x5265c00","tlc_fee_proportional_millionths":"0x3e8"}]},"id":3

   Why is the local_balance 0xa32aef600 (43,800,000,000) and the remote_balance 0x460913c00 (18,800,000,000)?

   This channel was established with nodeA contributing 500 ckb and node1 contributing 250 ckb.

   Since each cell requires a minimum of 98 ckb, this amount is reserved to ensure that there are sufficient funds to cover cell occupancy costs during on-chain settlement (when the channel closes). These 98 ckb will be returned to their respective nodes at the time of on-chain settlement.

   Actual available funds in the channel:

   nodeA: 500 ckb - 98 ckb = 402 ckb (local_balance is 0xa32aef600)

   node1: 250 ckb - 98 ckb = 152 ckb (remote_balance is 0x460913c00)

4. Call the new_invoice API on node2 to generate an invoice

   Multi-hop Payment Prerequisite

   This is a multi-hop payment (nodeA → node1 → node2). For this to work, node1 must already have an established channel with node2. The public testnet nodes (node1 and node2) already have channels between them, so you can proceed directly.

   If you're testing with your own nodes, make sure the intermediate node has a channel connected to the target node first.

   Set the amount to 0x5f5e100 (100,000,000 shannon), which is equivalent to 1 CKB. The payment_preimage should be a unique 32-byte hexadecimal number.

   # Generate a 32-byte random number and represent it in hexadecimal
   payment_preimage="0x$(openssl rand -hex 32)"
   echo $payment_preimage

   0xbc03e507befb33cfd5953a2e7046428e69cb8f0ade65c05d3661128aa4b4fff9

   Using CLI (on node2's host):

   ./fnn-cli --url http://18.163.221.211:8227 invoice new_invoice \
     --amount 100000000 \
     --currency Fibt \
     --description "test invoice generated by node2" \
     --expiry 3600 \
     --payment-preimage 0xbc03e507befb33cfd5953a2e7046428e69cb8f0ade65c05d3661128aa4b4fff9

   Using RPC:

   curl -s --location 'http://18.163.221.211:8227' --header 'Content-Type: application/json' --data '{
       "id": 4,
       "jsonrpc": "2.0",
       "method": "new_invoice",
       "params": [
           {
               "amount": "0x5f5e100",
               "currency": "Fibt",
               "description": "test invoice generated by node2",
               "expiry": "0xe10",
               "payment_preimage": "0xbc03e507befb33cfd5953a2e7046428e69cb8f0ade65c05d3661128aa4b4fff9",
               "hash_algorithm": "sha256"
           }
       ]
   }'

   {"jsonrpc":"2.0","result":{"invoice_address":"fibt1000000001peseucdphcxgfw0pnm6vk3uftyc36dakyjchs0p0unk9gaug0h36uhafww9pvy38gcesad084rx48xgx9xts49yp9fn87yfchld3l3qu5n0pfzvvy8c9g7dksrcxyrtk3hymspezmvtx4vg5v6uvt6tyxmq5uhrfejpk0j6wue9ef2pa8mzmrgqaz3wucutujtjcmq2x8f36faxuctg62ny73mhaj7rpwqe0ns0wp5wr4tku7qcl9r4a3swluvd2jqqwmsl7wsz4cwvhhe7p8tr7hz5qkqwr3r38hukckqzjtmntd8zrz0ywux4u8df005hl76thzsp9hz7dyefzk4mqhx4x9el98zjzmhcveqpfeur79","invoice":{"currency":"Fibt","amount":"0x5f5e100","signature":"0e1b101f1e0e100215180e0c1717191e01070b031e1702140016000e0311031107171c1618160002120b1b130b0d070203020f040e1c06151c070d090f0f14171f1e1a0b170210010517021e0d0419090216151b001706150605191f05070212021b17180c190001","data":{"timestamp":"0x1958944fa64","payment_hash":"0xafb604f74c28009732ed4c82983cf1efaddf62ee36442f360fb4a8c79b845432","attrs":[{"description":"test invoice generated by node2"},{"expiry_time":{"secs":3600,"nanos":0}},{"hash_algorithm":"sha256"},{"payee_public_key":"0291a6576bd5a94bd74b27080a48340875338fff9f6d6361fe6b8db8d0d1912fcc"}]}}},"id":4}

   Record the invoice_address from the response.

5. Before nodeA sends the payment, first query the local_balance and remote_balance of each channel

   nodeA ⟺ node1

   As shown in Step 3, the response included: {"local_balance":"0xa32aef600","remote_balance":"0x460913c00"}

   node1 ⟺ node2

   Using CLI:

   ./fnn-cli --url http://18.162.235.225:8227 channel list_channels

   Using RPC:

   curl -s --location 'http://18.162.235.225:8227' --header 'Content-Type: application/json' --data '{
       "id": 5,
       "jsonrpc": "2.0",
       "method": "list_channels",
       "params": [
           {
               "peer_pubkey": "<node2_pubkey>"
           }
       ]
   }'

   {"jsonrpc":"2.0","result":{"channels":[{"channel_id":"0x29a2e93e70fcfcd8b64fd74646b3893247f2a73a9dd8706298b5defa17bfee0a","is_public":true,"channel_outpoint":"0xa065311059be4d2194d9d6dbc428fe794ed3c6d91e08fe1d960d1574c19f88d400000000","peer_pubkey":"<node2_pubkey>","funding_udt_type_script":{"code_hash":"0x1142755a044bf2ee358cba9f2da187ce928c91cd4dc8692ded0337efa677d21a","hash_type":"type","args":"0x878fcc6f1f08d48e87bb1c3b3d5083f23f8a39c5d5c764f253b55b998526439b"},"state":{"state_name":"CHANNEL_READY","state_flags":[]},"local_balance":"0x173c0e06bb","offered_tlc_balance":"0x1f5","remote_balance":"0xc68e145","received_tlc_balance":"0x0","latest_commitment_transaction_hash":"0x195e1cbd1dd062752e776a44dd9c12f3b83a69dfdd1e22edff19025572bcbd25","created_at":"0x1944491c154","enabled":true,"tlc_expiry_delta":"0x5265c00","tlc_fee_proportional_millionths":"0x3e8"},{"channel_id":"0x4cd5bdcac419b203fd5752c4daa00a6f24305123d65f7a7fa6b455df82e97eee","is_public":true,"channel_outpoint":"0xe7d8464be26933021810f31252a98e9b2b1ff00f70173fafb134861ce21bccbb00000000","peer_pubkey":"<node2_pubkey>","funding_udt_type_script":{"code_hash":"0x1142755a044bf2ee358cba9f2da187ce928c91cd4dc8692ded0337efa677d21a","hash_type":"type","args":"0x878fcc6f1f08d48e87bb1c3b3d5083f23f8a39c5d5c764f253b55b998526439b"},"state":{"state_name":"CHANNEL_READY","state_flags":[]},"local_balance":"0x1748630df7","offered_tlc_balance":"0x0","remote_balance":"0x13da09","received_tlc_balance":"0x0","latest_commitment_transaction_hash":"0x6bd9890fd65297359079d87a995d794becc90bafd5eca9676ccbfd96abcb3ffd","created_at":"0x194448fc295","enabled":true,"tlc_expiry_delta":"0x5265c00","tlc_fee_proportional_millionths":"0x3e8"},{"channel_id":"0x9e72e8dbf7409a5aaf456dbe25f61247450f72079249ee508bb23cb14d0408b1","is_public":true,"channel_outpoint":"0x49f5f1cf664d48df66943989ef87d1316f1dffe5aec96db9ee8f1b6879ccac1b00000000","peer_pubkey":"<node2_pubkey>","funding_udt_type_script":null,"state":{"state_name":"CHANNEL_READY","state_flags":[]},"local_balance":"0x45a9b5cf3","offered_tlc_balance":"0x0","remote_balance":"0x916e2dc010d","received_tlc_balance":"0x0","latest_commitment_transaction_hash":"0x195e1cbd1dd062752e776a44dd9c12f3b83a69dfdd1e22edff19025572bcbd25","created_at":"0x1944491c154","enabled":true,"tlc_expiry_delta":"0x5265c00","tlc_fee_proportional_millionths":"0x3e8"}]},"id":5}

   Find all entries in the response where funding_udt_type_script is null.

   {"local_balance":"0x45a9b5cf3","remote_balance":"0x916e2dc010d"}
   {"local_balance":"0x504f21d045c","remote_balance":"0x4164b5a59a4"}
   {"local_balance":"0x916d6f044e9","remote_balance":"0x466871917"}
   {"local_balance":"0x48ab5ace976","remote_balance":"0x49087ca748a"}
   {"local_balance":"0x48ab5acd200","remote_balance":"0x49087ca8c00"}

6. Send a send_payment request to nodeA to pay node2

   Pass in the previously recorded invoice_address to the send_payment request

   Using CLI:

   ./fnn-cli payment send_payment --invoice "fibt1000000001peseucdphcxgfw0pnm6vk3uftyc36dakyjchs0p0unk9gaug0h36uhafww9pvy38gcesad084rx48xgx9xts49yp9fn87yfchld3l3qu5n0pfzvvy8c9g7dksrcxyrtk3hymspezmvtx4vg5v6uvt6tyxmq5uhrfejpk0j6wue9ef2pa8mzmrgqaz3wucutujtjcmq2x8f36faxuctg62ny73mhaj7rpwqe0ns0wp5wr4tku7qcl9r4a3swluvd2jqqwmsl7wsz4cwvhhe7p8tr7hz5qkqwr3r38hukckqzjtmntd8zrz0ywux4u8df005hl76thzsp9hz7dyefzk4mqhx4x9el98zjzmhcveqpfeur79"

   Using RPC:

   curl -s --location 'http://127.0.0.1:8227' --header 'Content-Type: application/json' --data '{
       "id": 6,
       "jsonrpc": "2.0",
       "method": "send_payment",
       "params": [
           {
               "invoice": "fibt1000000001peseucdphcxgfw0pnm6vk3uftyc36dakyjchs0p0unk9gaug0h36uhafww9pvy38gcesad084rx48xgx9xts49yp9fn87yfchld3l3qu5n0pfzvvy8c9g7dksrcxyrtk3hymspezmvtx4vg5v6uvt6tyxmq5uhrfejpk0j6wue9ef2pa8mzmrgqaz3wucutujtjcmq2x8f36faxuctg62ny73mhaj7rpwqe0ns0wp5wr4tku7qcl9r4a3swluvd2jqqwmsl7wsz4cwvhhe7p8tr7hz5qkqwr3r38hukckqzjtmntd8zrz0ywux4u8df005hl76thzsp9hz7dyefzk4mqhx4x9el98zjzmhcveqpfeur79"
           }
       ]
   }'

   {"jsonrpc":"2.0","result":{"payment_hash":"0xafb604f74c28009732ed4c82983cf1efaddf62ee36442f360fb4a8c79b845432","status":"Created","created_at":"0x1958957cc7d","last_updated_at":"0x1958957cc7d","failed_error":null,"fee":"0x186a0"},"id":6}

7. Repeat Steps 4 and 6 two more times

   Performing two additional new_invoice and send_payment requests, keeping the amount set to 0x5f5e100.

8. Query the local_balance and remote_balance of each channel again

   nodeA ⟺ node1

   Balances changed from{"local_balance":"0xa32aef600","remote_balance":"0x460913c00"}to{"local_balance":"0xa2cb78e60","remote_balance":"0x46688a3a0"}.

   node1 ⟺ node2

   Balances changed from {"local_balance":"0x48ab5acd200","remote_balance":"0x49087ca8c00"}to{"local_balance":"0x48aa3cb2f00","remote_balance":"0x49099ac2f00"}.

   All other entries remain unchanged.

   This means the channel balances have changed as follows before and after the payments:

   • Before payments

     nodeA (43800000000) ⟺ node1 (18800000000)

     node1 (4993800000000) ⟺ node2 (5018800000000)

   • After payments

     nodeA (43499700000) ⟺ node1 (19100300000)

     node1 (4993500000000) ⟺ node2 (5019100000000)

   Funds changes:

   nodeA: 43499700000 - 43800000000 = -300300000

   node1: 4993500000000 + 19100300000 - 4993800000000 - 18800000000 = 300000

   node2: 5019100000000 - 5018800000000 = 300000000

   Conclusion: Three CKB payments of 100,000,000 shannon each from nodeA → node1 → node2 were successfully completed. The intermediate node (node1) earned a total fee of 300,000 shannon.

9. Close the channel between nodeA and node1

   Pass in the channel_id and the receiving address as parameters.

   Using CLI:

   ./fnn-cli channel shutdown_channel \
     --channel-id 0x26ce85d57fb4a1a826cbf4862358862317a83b775090625550d8be12c6ce9569 \
     --close-script '{"code_hash":"0x9bd7e06f3ecf4be0f2fcd2188b23f1b9fcc88e5d4b65a8637b17723bbda3cce8","hash_type":"type","args":"0xcc015401df73a3287d8b2b19f0cc23572ac8b14d"}'

   Using RPC:

   curl -s --location 'http://127.0.0.1:8227' --header 'Content-Type: application/json' --data '{
       "id": 9,
       "jsonrpc": "2.0",
       "method": "shutdown_channel",
       "params": [
           {
               "channel_id": "0x26ce85d57fb4a1a826cbf4862358862317a83b775090625550d8be12c6ce9569",
               "close_script": {
                   "code_hash": "0x9bd7e06f3ecf4be0f2fcd2188b23f1b9fcc88e5d4b65a8637b17723bbda3cce8",
                   "hash_type": "type",
                   "args": "0xcc015401df73a3287d8b2b19f0cc23572ac8b14d"
               },
               "fee_rate": "0x3FC"
           }
       ]
   }'

   {"jsonrpc":"2.0","result":null,"id":9}

   You can see on the CKB explorer that nodeA's address received a new transaction of +496.99699462 CKB. This indicates that multiple off-chain CKB transfers through Fiber nodes are eventually settled on-chain upon channel closure via the shutdown_channel request.

Establishing a UDT Channel with Public Node 1

1. Establish a network connection between nodeA and node1

   Using CLI:

   ./fnn-cli peer connect_peer --address "/ip4/18.162.235.225/tcp/8119/p2p/QmXen3eUHhywmutEzydCsW4hXBoeVmdET2FJvMX69XJ1Eo"

   Using RPC:

   curl -s --location 'http://127.0.0.1:8227' --header 'Content-Type: application/json' --data '{
       "id": 1,
       "jsonrpc": "2.0",
       "method": "connect_peer",
       "params": [
           {
               "pubkey": "<node1_pubkey>",
               "address": "/ip4/18.162.235.225/tcp/8119/p2p/QmXen3eUHhywmutEzydCsW4hXBoeVmdET2FJvMX69XJ1Eo"
           }
       ]
   }'

2. Establish a channel with 20 RUSD: nodeA (20 RUSD) ⟺ node1 (0)

   Node1 has auto_accept_amount for RUSD set to 20 RUSD, so please input 20 RUSD or more as the funding_amount.

   Using CLI:

   ./fnn-cli channel open_channel \
     --pubkey <node1_pubkey> \
     --funding-amount 20 \
     --public true \
     --funding-udt-type-script '{"code_hash":"0x1142755a044bf2ee358cba9f2da187ce928c91cd4dc8692ded0337efa677d21a","hash_type":"type","args":"0x878fcc6f1f08d48e87bb1c3b3d5083f23f8a39c5d5c764f253b55b998526439b"}'

   Using RPC:

   curl -s --location 'http://127.0.0.1:8227' --header 'Content-Type: application/json' --data '{
       "id": 2,
       "jsonrpc": "2.0",
       "method": "open_channel",
       "params": [
           {
               "pubkey": "<node1_pubkey>",
               "funding_amount": "0x2540be400",
               "public": true,
               "funding_udt_type_script": {
                   "code_hash": "0x1142755a044bf2ee358cba9f2da187ce928c91cd4dc8692ded0337efa677d21a",
                   "hash_type": "type",
                   "args": "0x878fcc6f1f08d48e87bb1c3b3d5083f23f8a39c5d5c764f253b55b998526439b"
               }
           }
       ]
   }'

   {"jsonrpc":"2.0","result":{"temporary_channel_id":"0xa3137338377b67ea90c2f2c15b7d60ad27b3e891095f4b093772d7db3aa79344"},"id":2}

3. Query the channels between nodeA and node1

   Using CLI:

   ./fnn-cli channel list_channels

   Using RPC:

   curl -s --location 'http://127.0.0.1:8227' --header 'Content-Type: application/json' --data '{
       "id": 3,
       "jsonrpc": "2.0",
       "method": "list_channels",
       "params": [
           {
               "peer_pubkey": "<node1_pubkey>"
           }
       ]
   }'

   {"jsonrpc":"2.0","result":{"channels":[{"channel_id":"0x75dce35923a79086afd0f81b0134ac87619756b6c04a15669ce232aa7db142d8","is_public":true,"channel_outpoint":"0x8e133056792766e1fd34e870fb33990b58c4ebb9615526b38dacdf3686cf6d3f00000000","peer_pubkey":"<node1_pubkey>","funding_udt_type_script":{"code_hash":"0x1142755a044bf2ee358cba9f2da187ce928c91cd4dc8692ded0337efa677d21a","hash_type":"type","args":"0x878fcc6f1f08d48e87bb1c3b3d5083f23f8a39c5d5c764f253b55b998526439b"},"state":{"state_name":"ChannelReady","state_flags":[]},"local_balance":"0x2540be400","offered_tlc_balance":"0x0","remote_balance":"0x0","received_tlc_balance":"0x0","latest_commitment_transaction_hash":"0x2b0b36c5db14778484358a4641bfe00a4f351660c280255ef8e8538898e399d0","created_at":"0x1958977b7be","enabled":true,"tlc_expiry_delta":"0x5265c00","tlc_fee_proportional_millionths":"0x3e8"}]},"id":3}

4. Call the new_invoice API on node2 to generate an invoice

   Set the amount to 0x5f5e100 (100,000,000), which is equivalent to 1 RUSD.

   Here, a unique payment_preimage is still required. You can generate one using: echo "0x$(openssl rand -hex 32)"

   Using CLI (on node2's host):

   ./fnn-cli --url http://18.163.221.211:8227 invoice new_invoice \
     --amount 100000000 \
     --currency Fibt \
     --description "test invoice generated by node2" \
     --expiry 3600 \
     --udt-type-script '{"code_hash":"0x1142755a044bf2ee358cba9f2da187ce928c91cd4dc8692ded0337efa677d21a","hash_type":"type","args":"0x878fcc6f1f08d48e87bb1c3b3d5083f23f8a39c5d5c764f253b55b998526439b"}'

   Using RPC:

   curl -s --location 'http://18.163.221.211:8227' --header 'Content-Type: application/json' --data '{
       "id": 4,
       "jsonrpc": "2.0",
       "method": "new_invoice",
       "params": [
           {
               "amount": "0x5f5e100",
               "currency": "Fibt",
               "description": "test invoice generated by node2",
               "expiry": "0xe10",
               "payment_preimage": "0xf7d121b132b4f53bb8301591028b34fccc065f92161bb6e7d41cf6d32ad32a22",
               "hash_algorithm": "sha256",
               "udt_type_script": {
                   "code_hash": "0x1142755a044bf2ee358cba9f2da187ce928c91cd4dc8692ded0337efa677d21a",
                   "hash_type": "type",
                   "args": "0x878fcc6f1f08d48e87bb1c3b3d5083f23f8a39c5d5c764f253b55b998526439b"
               }
           }
       ]
   }'

   {"jsonrpc":"2.0","result":{"invoice_address":"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","invoice":{"currency":"Fibt","amount":"0x5f5e100","signature":"161b1405170f18161b1e1c090c0a0a010a190409061c1b1a1107130413040f1a0204080504121212150f1b031b171a040417030102191d010a1317090f1f1c120e1909121b0d041b17101f071e1b020d170a151a15121d0d081d12151816171c0d000215190a1801","data":{"timestamp":"0x1958e785913","payment_hash":"0x6a356ad088b704a9c53728029bd968e894daf5adab1da838bf06f6755239b005","attrs":[{"description":"test invoice generated by node2"},{"expiry_time":{"secs":3600,"nanos":0}},{"udt_script":"0x550000001000000030000000310000001142755a044bf2ee358cba9f2da187ce928c91cd4dc8692ded0337efa677d21a0120000000878fcc6f1f08d48e87bb1c3b3d5083f23f8a39c5d5c764f253b55b998526439b"},{"hash_algorithm":"sha256"},{"payee_public_key":"0291a6576bd5a94bd74b27080a48340875338fff9f6d6361fe6b8db8d0d1912fcc"}]}}},"id":4}

5. Before nodeA sends the payment, first query the local_balance and remote_balance of each channel

   nodeA ⟺ node1

   As shown in Step 3, the response included: {"local_balance":"0x77359400","remote_balance":"0x0"}

   node1 ⟺ node2

   Using CLI:

   ./fnn-cli --url http://18.162.235.225:8227 channel list_channels

   Using RPC:

   curl -s --location 'http://18.162.235.225:8227' --header 'Content-Type: application/json' --data '{
       "id": 5,
       "jsonrpc": "2.0",
       "method": "list_channels",
       "params": [
           {
               "peer_pubkey": "<node2_pubkey>"
           }
       ]
   }'

   Find all entries in the response where funding_udt_type_script is not null.

   {"local_balance":"0x172a2c63bb","remote_balance":"0x1e4a8445"}
   {"local_balance":"0x1748630df7","remote_balance":"0x13da09"}
   {"local_balance":"0xa38b9d","remote_balance":"0x1747d35c63"}
   {"local_balance":"0xc505f","remote_balance":"0x17486a97a1"}

6. Send a send_payment request to nodeA to pay node2

   Using CLI:

   ./fnn-cli payment send_payment --invoice "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"

   Using RPC:

   curl -s --location 'http://127.0.0.1:8227' --header 'Content-Type: application/json' --data '{
       "id": 6,
       "jsonrpc": "2.0",
       "method": "send_payment",
       "params": [
           {
               "invoice": "fibt1000000001px88ja42xcmczxzat8lhtuq9f29ga8x244qk737nl4r7lq8aw7y7puhjn6jp50xsd2c6ndfxkmn5wnl4z8clk7fej9trwx0gjlmtvnj2wqwlvcu0eekzqvtehlc42t8lpstmgc7ntskh5ef36f8hgvck8c9pescktlx05fpuaceews94kvyrvgf87gvd9wnmh86puzyz2vp6h6jppt8lsq5u8tc87y6szha9587f90dmlmwt5mtetxz9ekukxu6x7s2fyuuy2re0etzzksqnt8rtr5925qypz2224j5xf56nlscnmtvcvywdxg40hsy5w5xt40d5cdest3kvhqswfftfc3qqs7plhlk7m5n9hyzqws9qlxw2huurg7l6c4q9evyg7fljcl3cqh3h3ecpg3fue3cq4slpxapvc2uye6jl77sfcflc8jf8fvr4qwly9wxuyehqf573hu454qy92wqke0hdgrvm7y83sgspn4a29h69s7ucp4cedle"
           }
       ]
   }'

   {"jsonrpc":"2.0","result":{"payment_hash":"0x6a356ad088b704a9c53728029bd968e894daf5adab1da838bf06f6755239b005","status":"Created","created_at":"0x1958e7b66b5","last_updated_at":"0x1958e7b66b5","failed_error":null,"fee":"0x186a0"},"id":6}

7. Repeat Steps 4 and 6 two more times

   Performing two additional new_invoice and send_payment requests, keeping the amount set to 0x5f5e100.

8. Query the local_balance and remote_balance of each channel again

   nodeA ⟺ node1

   Balances changed from{"local_balance":"0x77359400","remote_balance":"0x0"}to{"local_balance":"0x654f5d20","remote_balance":"0x11e636e0"}.

   node1 ⟺ node2

   Balances changed from{"local_balance":"0x172a2c63bb","remote_balance":"0x1e4a8445"}to{"local_balance":"0x17184ac0bb","remote_balance":"0x302c2745"}.

   All other entries remain unchanged.

   This means the channel balances have changed as follows before and after the payments:

   • Before payments

     nodeA (2000000000) ⟺ node1 (0)

     node1 (99491799995) ⟺ node2 (508200005)

   • After payments

     nodeA (1699700000) ⟺ node1 (300300000)

     node1 (99191799995) ⟺ node2 (808200005)

   Funds changes:

   nodeA: 1699700000 - 2000000000 = -300300000

   node1: 99191799995 + 300300000 - 99491799995 = 300000

   node2: 808200005 - 508200005 = 300000000

   Conclusion: Three UDT payments of 100,000,000 each from nodeA → node1 → node2 were successfully completed. The intermediate node (node1) earned a total fee of 300,000.

9. Close the channel between nodeA and node1

   Using CLI:

   ./fnn-cli channel shutdown_channel \
     --channel-id 0x75dce35923a79086afd0f81b0134ac87619756b6c04a15669ce232aa7db142d8 \
     --close-script '{"code_hash":"0x9bd7e06f3ecf4be0f2fcd2188b23f1b9fcc88e5d4b65a8637b17723bbda3cce8","hash_type":"type","args":"0xcc015401df73a3287d8b2b19f0cc23572ac8b14d"}'

   Using RPC:

   curl -s --location 'http://127.0.0.1:8227' --header 'Content-Type: application/json' --data '{
       "id": 9,
       "jsonrpc": "2.0",
       "method": "shutdown_channel",
       "params": [
           {
               "channel_id": "0x75dce35923a79086afd0f81b0134ac87619756b6c04a15669ce232aa7db142d8",
               "close_script": {
                   "code_hash": "0x9bd7e06f3ecf4be0f2fcd2188b23f1b9fcc88e5d4b65a8637b17723bbda3cce8",
                   "hash_type": "type",
                   "args": "0xcc015401df73a3287d8b2b19f0cc23572ac8b14d"
               },
               "fee_rate": "0x3FC"
           }
       ]
   }'

   {"jsonrpc":"2.0","result":null,"id":9}

   You can see on the CKB explorer that nodeA's address received a new transaction of +16.997 RUSD. This indicates that multiple off-chain UDT transfers through Fiber nodes are eventually settled on-chain upon channel closure via the shutdown_channel request.