Ethcall

Ethcall, in the context of Ethereum, refers to the JSON-RPC method eth_call used to execute a contract function locally on a node without changing the blockchain state. It allows clients to read contract data, simulate function outputs, and test interactions without submitting a transaction or incurring gas costs.

The eth_call method takes two parameters: a call object and a block tag. The call object describes the hypothetical transaction to be executed and commonly includes fields such as from, to, gas, gasPrice, value, and data. The from field can influence contract logic that depends on the caller, while the to field is the target contract address. The gas field sets the maximum gas allowed for the simulated execution. The value field represents the amount of Ether sent with the call, and data carries the function selector and parameters. The block tag specifies the state of the blockchain to use for the simulation, with values like latest, pending, or a specific block number.

The response to eth_call is the return data from the contract function, encoded as a hex string. If the execution reverts or encounters an error, the node may return an error object or a revert message, depending on the client implementation. Importantly, eth_call does not modify any state on the blockchain, and it does not create a transaction or incur real transaction costs.

Common use cases include reading contract state, querying function outputs, and verifying what a function would return before sending a transaction. For state-changing operations, other methods such as eth_sendTransaction or eth_estimateGas are used instead.