Flare uses Athereum, a friendly fork of Ethereum that runs the EVM with some additional features provided by the Avalanche Platform. Since Flare is fully EVM-compatible, you can use Ethereum's JSON-RPC API to interact with the Flare Network. Check out the documentation on Ethereum's JSON-RPC API to learn more about the JSON-RPC protocol. The JSON-RPC API is a foundational data transfer protocol for interacting with any EVM-based network. JSON-RPC is the primary protocol to interact with an Athereum/Ethereum client. Libraries in other languages, such as Web3.js, are wrappers around JSON-RPC.
In this guide, we will interact with Flare's Coston Test Network using a commanline terminal. The JSON-RPC endpoint for the testnet is https://coston.flare.network/ext/bc/C/rpc.
Any of the JSON-RPC methods described in the Ethereum Wiki mentioned above can be used with Flare. Here is an example of calling the JSON-RPC API using curl:
$ curl -X POST https://coston.flare.network/ext/bc/C/rpc \
--data '{"jsonrpc": "2.0", "method": "web3_clientVersion", "params":[], "id":67 }' \
-H "Content-Type: application/json"
{"jsonrpc":"2.0","id":67,"result":"Athereum 1.0"}
The testnet response for the web3_clientVersion method us shows that the EVM uses the JSON-RPC 2.0 Specification. The client, which is a software implementation of Athereum, responds with information about the testnet node that we are connecting to through the endpoint.
There are a lot of great API methods so I recommend that you take a look at the full list. Let's take a look at some more examples:
Returns a list of addresses owned by the client.
$ curl -X POST https://coston.flare.network/ext/bc/C/rpc \
--data '{"jsonrpc": "2.0", "method": "eth_accounts", "params":[],"id": 67}' \
-H "Content-Type: application/json" \
| python -m json.tool
{
"id": 67,
"jsonrpc": "2.0",
"result": [
"0xdd5f754dc228450e818a2af8e412426feb954ce4",
"0x02e1c8693e1ceb256f295515df1fb731edf399a8",
"0x562b24f340c082771b27f285db979f0e3eb81cee",
"0xb3bb6397c235c569d5cb405c1a3f81112b04612b",
"0x543ed104265ae2f19f01c98ed5d9210632091dcc",
"0xe3760fc9bacf3574da5358486ea2d82d358c04b7",
"0x519ae06912d23588cf5b71e19064cfd1fa381758",
"0xcea79be98b0e3e101ef33ba16210f283eecf4988",
"0x44cfee2a75c57647add67828db92f7864a5b0be6",
"0x73fc45a2f61fa3f99a65b5e23feba3a243f88b21",
"0x8fff43c6c83fc9ec844a9781d4f3f1093c9e6a7c"
]
}
Returns the number of the most recent block.
$ curl -X POST https://coston.flare.network/ext/bc/C/rpc \
--data '{"jsonrpc": "2.0", "method": "eth_blockNumber", "params":[],"id": 67}' \
-H "Content-Type: application/json"
{"jsonrpc":"2.0","id":67,"result":"0x388a4"}
Some results are encoded in hex format and prefixed with 0x. To decode the actual value, there are several options. One option is to use the JavaScript console:
> parseInt('0x388a4', 16)
231588
It can also be decoded via the commandline with Python:
$ python -c "print int('0x388a4', 16)"
231588
We can now see that the most recent block is number 231588.
Returns information about the specified block. Note that the parameter expects a hex-encoded number.
$ curl -X POST https://coston.flare.network/ext/bc/C/rpc \
--data '{"jsonrpc": "2.0", "method": "eth_getBlockByNumber", "params": ["0x388a4", true],"id": 67}' \
-H "Content-Type: application/json"
{
"id": 67,
"jsonrpc": "2.0",
"result": {
"difficulty": "0x1",
"extraData": "0xd883010903846765746888676f312e31342e32856c696e7578d6dd3e6e27472e544f805783de8ff48f84b5147ac38cd0191f84ff9b9f161d6a",
"gasLimit": "0x7a1200",
"gasUsed": "0x5208",
"hash": "0x69ad4fbb5cda48271d6daba112d44ddf52b6c4f4a7f1cef1b9bff84a56de4f29",
"logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
"miner": "0x0100000000000000000000000000000000000000",
"mixHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
"nonce": "0x0000000000000000",
"number": "0x388a4",
"parentHash": "0x6284ee941c7b641865bb52271dacbe9770d6f218e3f81a38bba30c055dea4bb0",
"receiptsRoot": "0x056b23fbba480696b65fe5a59b8f2148a1299103c4f57df839233af2cf4ca2d2",
"sha3Uncles": "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",
"size": "0x2ad",
"stateRoot": "0x05ef08b75ef358cbb4001c1dca21717f6a9c4e3c1d3415df85f6ed961e6c72cc",
"timestamp": "0x602d7621",
"totalDifficulty": "0x388a4",
"transactions": [
{
"blockHash": "0x69ad4fbb5cda48271d6daba112d44ddf52b6c4f4a7f1cef1b9bff84a56de4f29",
"blockNumber": "0x388a4",
"from": "0x1c22a9dc4bfe93c49bba31c36a887c01b5eba265",
"gas": "0x33450",
"gasPrice": "0x4a817c800",
"hash": "0x0c80fb2a0086701992c14a36690fb3fb01fa640410c1e2765a7d9ca388892b66",
"input": "0x",
"nonce": "0xbce5",
"r": "0xb79d3aa808781c4257e598dccbbbb50cddccdf6de2372077cc07862a3f66218e",
"s": "0x1b2d12d868780633ff793db4b3a225786ce61efb88de08d7cd171bfde43c28c4",
"to": "0x0a218d00e8a71dbd8240758e062422c7f565ec6a",
"transactionIndex": "0x0",
"v": "0x25",
"value": "0xde0b6b3a7640000"
}
],
"transactionsRoot": "0x3c413200f2845f9ae816a093c3098378e0b1b90faff36c34afe4a496e99625c0",
"uncles": []
}
}
Gets the balance for an account in wei (1 Spark = 10^18 wei).
$ curl -X POST https://coston.flare.network/ext/bc/C/rpc \
--data '{"jsonrpc": "2.0", "method": "eth_getBalance", "params":["0xb7b685dD1b52D2939bD6f5d9515635c5a633fFAA", "latest"],"id": 67}' \
-H "Content-Type: application/json"
{"jsonrpc":"2.0","id":67,"result":"0x277370eb4dcb872296277e34800"}
$ python -c "print '{:.4f}'.format(int('0x277370eb4dcb872296277e34800', 16) * 10**-18)"
50010010001099.9922
The Python command formats the account balance to Spark.