How to call API in solidity with ethereum private network - ethereum

Question

I'm trying to call external API in smart contract code with Ethereum private network but didn't get any solution.
I have also gone through chainlink solutions but I didn't get oracle id and job id from markt.link as per latest website update.
Can someone please help me out on how to make HTTP get/post requests in solidity with Ethereum private network?

Answer 1

Solidity is compiled to EVM (Ethereum Virtual Machine) bytecode. To keep all operations deterministic, the code running inside the VM cannot communicate with resources outside of the VM.
Having said that, there are services such as Chainlink, allowing you to communicate with external APIs from Solidity code on public networks. When you invoke a specific Chainlink SDK function passing it an API URL and other params, it emits Solidity event. Their offchain app is listening to this event, queries the URL and sends back a new transaction to your contract, containing the result.
There are no Chainlink nodes on your private network. So on a private network, you can replicate this approach with your own offchain application.
Solidity:
pragma solidity ^0.8;
contract MyContract {
event DataRequested(string url);
function requestData(string memory url) public {
emit DataRequested(url);
}
function receiveData(bytes memory data) public {
// it's recommended to validate `msg.sender`
// and allow for this function to be invoked only from an authorized address
require(msg.sender == address(0x123));
}
}
JS:
const Web3 = require("web3");
const web3 = new Web3(YOUR_NODE_URL);
const myContract = new web3.eth.Contract(ABI, ADDRESS);
// handle the event when it's emitted
myContract.events.DataRequested(async (eventData) => {
// process the URL
const result = queryUrl(eventData.returnValues.url);
// send the data back from the authorized address
// your local `web3` instance or the node need to know the private key of `0x123` address
await myContract.methods.receiveData(result).send({
from: "0x123"
});
});