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RPCs

CKB RPCs are a set of programming interfaces provided by the Nervos CKB blockchain, enabling developers to interact with the network for querying data, managing transactions, and deploying smart contracts directly.

Public JSON RPC Nodes​

  • These nodes are provided by community members, they may be unstable, incomplete or not work at all, use at your own risk.
  • You may use these nodes to try out or test some features, but you should not use them for production.
  • Since ckb v0.105.0, ckb already included indexer service, just use ckb jsonrpc url for indexer service.
TypeLink
Mainnethttps://mainnet.ckbapp.dev/
Mainnethttps://mainnet.ckb.dev/
Testnethttps://testnet.ckbapp.dev/
Testnethttps://testnet.ckb.dev/

RPC Provider: Ankr​

Ankr is an RPC provider that wors as intermediary to help you interact with the Nervos Network. You might experience some levels of latency depending on the provider’s location. Ankr’s endpoint root: https://rpc.ankr.com/nervos

CKB JSON-RPC Protocols​

CKB exposes a set of RPCs in JSON-RPC 2.0 protocols for interactions. For more details, please refer to CKB JSON RPC Protocols Documentation.

tip
  • The RPCs exposed by CKB are only designed for internal usage. Please limit the access to the CKB RPCs strictly to trusted machines (by using rpc.listen_address configuration option). Exposing CKB RPCs to the public Internet is dangerous and strongly discouraged.
  • CKB JSON-RPC only supports HTTP now. If you need SSL support, please setup a reverse proxy via nginx or other HTTPS servers.
  • Subscriptions require a full duplex connection. CKB offers such connections in the form of tcp (enable with rpc.tcp_listen_address configuration option) and websockets (enable with rpc.ws_listen_address), plain HTTP connection does not support subscriptions. See below for examples on this.

Basic Usage​

The following commands uses get_tip_block_number RPC to fetch the tip block number, of the latest block number in the longest blockchain:

echo '{
    "id": 2,
    "jsonrpc": "2.0",
    "method": "get_tip_block_number",
    "params": []
}' \
| tr -d '\n' \
| curl -H 'content-type: application/json' -d @- \
http://localhost:8114

The following commands uses send_transaction RPC to send transactions to the CKB network:

echo '{
  "id": 3,
  "jsonrpc": "2.0",
  "method": "send_transaction",
  "params": [
    {
      "cell_deps": [
        {
          "dep_type": "code",
          "out_point": {
            "index": "0x0",
            "tx_hash": "0xa4037a893eb48e18ed4ef61034ce26eba9c585f15c9cee102ae58505565eccc3"
          }
        }
      ],
      "header_deps": [
        "0x7978ec7ce5b507cfb52e149e36b1a23f6062ed150503c85bbf825da3599095ed"
      ],
      "inputs": [
        {
          "previous_output": {
            "index": "0x0",
            "tx_hash": "0x365698b50ca0da75dca2c87f9e7b563811d3b5813736b8cc62cc3b106faceb17"
          },
          "since": "0x0"
        }
      ],
      "outputs": [
        {
          "capacity": "0x2540be400",
          "lock": {
            "code_hash": "0x28e83a1277d48add8e72fadaa9248559e1b632bab2bd60b27955ebc4c03800a5",
            "hash_type": "data",
            "args": "0x"
          },
          "type": null
        }
      ],
      "outputs_data": [
        "0x"
      ],
      "version": "0x0",
      "witnesses": []
    }
  ]
}'\
| tr -d '\n' \
| curl -H 'content-type: application/json' -d @- \
http://localhost:8114

It should be noted that send_transaction is asynchronous, that is, the return of the transaction hash, does not mean that the transaction is fully verified, if you need to follow up on the status of the transaction, it is recommended to use the following get_transaction rpc：

echo '{
    "id": 4,
    "jsonrpc": "2.0",
    "method": "get_transaction",
    "params": ["0xa0ef4eb5f4ceeb08a4c8524d84c5da95dce2f608e0ca2ec8091191b0f330c6e3"]
}' \
| tr -d '\n' \
| curl -H 'content-type: application/json' -d @- \
http://localhost:8114

Subscription​

To use subscription feature, you need to configure CKB to enable such features. In this section, we assume you use the following configuration in CKB.tomlsection:

[rpc]
listen_address = "127.0.0.1:8114"
tcp_listen_address = "127.0.0.1:18114"
ws_listen_address = "127.0.0.1:18115"

# ... more configs

This above config ensures CKB listens at 8114 port for normal HTTP connections, 18114 port for TCP duplex connections, and 18115 port for WebSocket duplex connections.

TCP Based RPC​

The following command uses netcat to connect via TCP to CKB, then fire the same get_tip_block_number RPC as shown above to fetch the block number in the longest chain:

echo '{
    "id": 2,
    "jsonrpc": "2.0",
    "method": "get_tip_block_number",
    "params": []
}' \
| tr -d '\n' \
| sed -e "s/$/\n/"
| nc localhost 18114 -q 1
{"jsonrpc":"2.0","result":"0xdc90","id":2}

The following command uses netcat to connect to CKB, make a subscription request to monitor the latest committed block:

cat <(echo '{
    "id": 2,
    "jsonrpc": "2.0",
    "method": "get_tip_block_number",
    "params": []
}' \
| tr -d '\n' \
| sed -e "s/$/\n/") -
| nc localhost 18114
{"jsonrpc":"2.0","result":"0xa","id":2}
{"jsonrpc":"2.0","method":"subscribe","params":{"result":"{\"version\":\"0x0\",\"compact_target\":\"0x1a2810cf\",\"timestamp\":\"0x16ee81d0d5f\",\"number\":\"0x30673\",\"epoch\":\"0x5f102b400007a\",\"parent_hash\":\"0xc9020c79d4f19797022af3631eb9e76c57933bd608fe81a137b834975616c991\",\"transactions_root\":\"0x7d8e3c102a5c52598cdbe7d208deb986eb2f0af189bc4655e6dd1a71564c2b25\",\"proposals_hash\":\"0x0000000000000000000000000000000000000000000000000000000000000000\",\"uncles_hash\":\"0x0000000000000000000000000000000000000000000000000000000000000000\",\"dao\":\"0x15b9ae7648400f2fb61d57e0379b2300fc641b7e8db5160000060394d5580007\",\"nonce\":\"0x1f86f056000002460000000053170600\",\"hash\":\"0xa3c8feda83d7e184f09cb4f05e535bccd4c159e2cc0ac7a06ea7d457e0051a08\"}","subscription":"0xa"}}
{"jsonrpc":"2.0","method":"subscribe","params":{"result":"{\"version\":\"0x0\",\"compact_target\":\"0x1a2810cf\",\"timestamp\":\"0x16ee81d1dfd\",\"number\":\"0x30674\",\"epoch\":\"0x5f102b500007a\",\"parent_hash\":\"0xa3c8feda83d7e184f09cb4f05e535bccd4c159e2cc0ac7a06ea7d457e0051a08\",\"transactions_root\":\"0x6d2dfc88bd8dda743b5bae14453f5f405a2a29a3cf6fff00c60f0f5c60a84fbe\",\"proposals_hash\":\"0x0000000000000000000000000000000000000000000000000000000000000000\",\"uncles_hash\":\"0x0000000000000000000000000000000000000000000000000000000000000000\",\"dao\":\"0xb4e019376f400f2f34c172e7379b230031d1417d95b5160000a399ffd6580007\",\"nonce\":\"0xded8ffa1000000000000040a90000000\",\"hash\":\"0x7d10fd1fb459630aa2f87ee4de699b7466a5da6efc0aee6ff459ff17b6cc5904\"}","subscription":"0xa"}}
// ... more data

Use Ctrl-C to exit netcat here.

WebSocket Based RPC​

To play with WebSocket based RPC, please make sure to install wscat first:

npm install -g wscat

You can use the following command to start wscat and connect to CKB:

wscat -c ws://localhost:18115
Connected (press CTRL+C to quit)
>

Now we can run the same get_tip_block_number request as above:

> {"id": 2, "jsonrpc": "2.0", "method": "get_tip_block_number", "params": []}
< {"jsonrpc":"2.0","result":"0x76887","id":2}

You can also create subscriptions for new blocks:

> {"id": 2, "jsonrpc": "2.0", "method": "subscribe", "params": ["new_tip_header"]}                                                                                                        < {"jsonrpc":"2.0","result":"0x2","id":2}                                                                                                                                                 < {"jsonrpc":"2.0","method":"subscribe","params":{"result":"{\"version\":\"0x0\",\"compact_target\":\"0x1a216e17\",\"timestamp\":\"0x16f886b2223\",\"number\":\"0x77e2a\",\"epoch\":\"0x6c$01a9000135\",\"parent_hash\":\"0x2662c8056c638408d8f018a53785d68f633bd1edfa06b82d7c29ddcac1d98927\",\"transactions_root\":\"0xa6488b15373521ec0b1bc9dff1f117cc1cad7d3579e8a6c38cc6e35166dad9bd\",\"proposals_hash\":\"0x0000000000000000000000000000000000000000000000000000000000000000\",\"uncles_hash\":\"0x0000000000000000000000000000000000000000000000000000000000000000\",\"dao\":\"0x1a1aab41ad3eb72fa260f4eedeb9230092c4510af45b390000547d684fc40007\",\"nonce\":\"0xce1aaca681000089001d0003cb2d0500\",\"hash\":\"0x993e593921024167c1779146348fe2d82864ecd3f657b3bd2b14fbdfa87c4f06\"}","subscription":"0x2"}}
< {"jsonrpc":"2.0","method":"subscribe","params":{"result":"{\"version\":\"0x0\",\"compact_target\":\"0x1a216e17\",\"timestamp\":\"0x16f886b29e3\",\"number\":\"0x77e2b\",\"epoch\":\"0x6c601aa000135\",\"parent_hash\":\"0x993e593921024167c1779146348fe2d82864ecd3f657b3bd2b14fbdfa87c4f06\",\"transactions_root\":\"0xe64cb6afb57e92a2af1da34d8a1d547fcd8b833e187697ae28a9dfadaaeba247\",\"proposals_hash\":\"0x0000000000000000000000000000000000000000000000000000000000000000\",\"uncles_hash\":\"0xa807c9cbb16a5af7cf36fd5c20b29535f6db4de52062138ad21ea6790ba9529c\",\"dao\":\"0xba227d3fcf3eb72fc8d61ff5deb92300402b3f12fb5b390000f113d450c40007\",\"nonce\":\"0xfb68521601000000000000503c9e2338\",\"hash\":\"0xf55d0f7ae1d9b106eee96139d86313e46b109ec8fa0d92f9eb6eb8bc81c294ec\"}","subscription":"0x2"}}
< {"jsonrpc":"2.0","method":"subscribe","params":{"result":"{\"version\":\"0x0\",\"compact_target\":\"0x1a216e17\",\"timestamp\":\"0x16f886b40a3\",\"number\":\"0x77e2c\",\"epoch\":\"0x6c601ab000135\",\"parent_hash\":\"0xf55d0f7ae1d9b106eee96139d86313e46b109ec8fa0d92f9eb6eb8bc81c294ec\",\"transactions_root\":\"0xad2c9e1eabc586c8e38cc1eaca61eba5e320bbf4655c510c5be5de9eaafea96f\",\"proposals_hash\":\"0x0000000000000000000000000000000000000000000000000000000000000000\",\"uncles_hash\":\"0x0000000000000000000000000000000000000000000000000000000000000000\",\"dao\":\"0x5a2b4f3df13eb72feb4c4bfbdeb923008c922c1a025c3900008eaa3f52c40007\",\"nonce\":\"0x7b5ad85601000000000000005b340000\",\"hash\":\"0x2077e0c022514fe07844411436cfbf50e413694858a3d4775e0c836e787ce7ab\"}","subscription":"0x2"}}
<< // ... more data.

Serialization​

CKB's RPCs returns data in JSON format. While most fields are self-explanatory, CKB has special handling for numbers and binary data:

Numbers​

All numbers used in CKB's RPCs, including request parameters and return values, use hex encoding, the number is encoded first in hexadecimal in the most compact format(meaning useless leading zeros should be striped), and then prefixed with 0x. Here are some examples:

  • 0 is encoded as 0x0, we cannot remove the remaining 0 since otherwise it won't be a proper number
  • 4 is encoded as 0x4
  • 15 is encoded as 0xf
  • 42 is encoded as 0x2a
  • 291 is encoded as 0x123
  • 3984 is encoded as 0xf90

Binary Data​

All binary data, including all the hashes, args in script, outputs_data items, are represented as hex string with 0x prefix. Some examples include:

  • 0x65b253cdcb6226e7f8cffec5c47c959b3d74af2caf7970a1eb1500e9b92aa200
  • 0x927f3e74dceb87c81ba65a19da4f098b4de75a0d
  • 0x40420f00000000000000000000000000
  • 0x (empty data)

Unlike numbers, binary data should always have a even numbered length.