Calling a contract on the Portal network

Once you have a Fluffy node running and connected to the network with the JSON-RPC interface enabled, then you can call contracts using the eth_call JSON-RPC method which should be enabled by default.

Note that eth_call in Fluffy requires both the history network, state network and the eth rpc api to be enabled. These should be enabled by default already but you can also manually enable these by running:

./build/fluffy --rpc --portal-subnetworks=history,state --rpc-api=eth

Here is an example which calls one of the earliest contracts deployed on Ethereum, which allows you to write "graffiti" on the chain:

curl -s -X POST -H 'Content-Type: application/json' -d '{
    "jsonrpc": "2.0",
    "method": "eth_call",
    "id": 1,
    "params": [
        {
            "to": "0x6e38A457C722C6011B2dfa06d49240e797844d66",
            "input": "0xa888c2cd0000000000000000000000000000000000000000000000000000000000000007"
        },
        "0xF4240"
    ]
}' http://localhost:8545

Fluffy is able to call mainnet smart contracts without having to run a full execution client and without even having the state data stored locally.

It does this by first fetching the bytecode of the contract being called from the portal state network and then fetching the required accounts and storage slots from the network on demand while the transaction is executing. We use the Nimbus in memory EVM for this which is configured to fetch the data from the portal network instead of from a local database as is usually the case for a full node.

We also make use of certain optimizations to speed up the call such as caching of recently fetched content, and concurrent state downloads (where possible) but even with these improvements the response time may be slower compared to when using a regular full node or RPC provider due to the network latency of fetching the state from the portal network.

Note

The portal state network is still in active development and the historical state data is not yet available for the full Ethereum history. For this reason some JSON-RPC calls may fail if the data is not yet seeded into the network.