Ethereum data

Trin is designed to serve the JSON-RPC methods that an Ethereum full node would provide. This includes methods the start with the eth_ namespace. Note that not every method is implemented yet.

Here are some methods that are available:

Get Block By Number

Here is an example of making an eth_getBlockByNumber request to a node, to load the block details for block 20,987,654. (In hexadecimal representation, this number is 0x1403f06.)

{"jsonrpc": "2.0", "method": "eth_getBlockByNumber", "params": ["0x1403f06", false], "id": 1}

IPC

By default, trin serves the JSON-RPC methods over an IPC socket. The default location on Linux is /tmp/trin-jsonrpc.ipc.

Make the request in your shell with this one-liner:

BLOCK_NUM=20987654; echo '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["0x'$(printf "%x" $BLOCK_NUM)'", false],"id":1}' | nc -U /tmp/trin-jsonrpc.ipc | jq

Note the following steps in the one-liner above:

• Convert the block number from decimal to hexadecimal using printf
• Send the request to trin using nc
• format the response with jq (optional, for pretty printing)

HTTP

Trin can also serve the JSON-RPC methods over HTTP. It needs to be activated with the flag --web3-transport http. The default port is 8545.

BLOCK_NUM=20987654; curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["0x'$(printf "%x" $BLOCK_NUM)'", false],"id":1}' localhost:8545 | jq

Call a contract function

To read data out of a contract, use the eth_call method.

The data needed to make this call is well populated in the Portal Network for the first 1 million blocks, and is being expanded over time. To activate contract storage access, connect to the Portal state network by running trin with the flag --portal-subnetworks state,history.

Calling a contract fuction usually involves enough formatting that it's helpful to use a tool to build the request, like Web3.py.

Below is an example of one of the earliest contracts posted to Ethereum, which allows you to write "graffiti" on the chain.

Calling Contract with Python

The following python code reads the graffiti from entry 7 in the contract. We read this data (ie~ call this contract fuction) as it was available in block 1,000,000, which has the hash 0x8e38b4dbf6b11fcc3b9dee84fb7986e29ca0a02cecd8977c161ff7333329681e.

from web3 import Web3

# Connect to trin
w3 = Web3(Web3.IPCProvider('/tmp/trin-jsonrpc.ipc'))

# Generate the contract interface
contract = w3.eth.contract(
    address='0x6e38A457C722C6011B2dfa06d49240e797844d66',
    abi='[{"constant":false,"inputs":[],"name":"number_of_claims","outputs":[{"name":"result","type":"uint256"}],"type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"claims","outputs":[{"name":"claimant","type":"address"},{"name":"message","type":"string"},{"name":"block_number","type":"uint256"}],"type":"function"},{"constant":false,"inputs":[{"name":"message","type":"string"}],"name":"claim","outputs":[],"type":"function"}]'
)

# Call the contract function
claim = contract.functions.claims(7).call(block_identifier='0x8e38b4dbf6b11fcc3b9dee84fb7986e29ca0a02cecd8977c161ff7333329681e')

print(f"claim graffiti: {claim}")

When running this python script, you should see the output:

claim graffiti: ['0xFb7Bc66a002762e28545eA0a7fc970d381863C42', 'Satisfy Values through Friendship and Ponies!', 50655]

This tells you that the 0xFb7Bc66a002762e28545eA0a7fc970d381863C42 address made the claim, shows you what they wrote, and shows which block number they made the claim in (50,655).

Call contract without Web3

Without a tool like Web3.py, you can build the JSON-RPC request manually. Here is an example of calling the same contract function as above manually:

echo '{"jsonrpc": "2.0", "method": "eth_call", "params": [{"to": "0x6e38A457C722C6011B2dfa06d49240e797844d66", "data": "0xa888c2cd0000000000000000000000000000000000000000000000000000000000000007"}, "0x8e38b4dbf6b11fcc3b9dee84fb7986e29ca0a02cecd8977c161ff7333329681e"], "id": 1}' | nc -U /tmp/trin-jsonrpc.ipc | jq

Which outputs:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x000000000000000000000000fb7bc66a002762e28545ea0a7fc970d381863c420000000000000000000000000000000000000000000000000000000000000060000000000000000000000000000000000000000000000000000000000000c5df000000000000000000000000000000000000000000000000000000000000002d536174697366792056616c756573207468726f75676820467269656e647368697020616e6420506f6e6965732100000000000000000000000000000000000000"
}

Decoding the result is left as an exercise to the reader.