JSON RPC ERROR: Gas Estimates error; Random

[Umair72Raza]

Hello, I need help in my dApp where I am using Reown appkit with Unity and polygon amoy testnet to deploy and interact with contracts.

I am new to blockchain and using Reown Appkit to interact with ERC 20 and ERC1155 contracts. I am connecting to my account using the wallet connect feature from the Reown Appkit Modal to connect my mobile wallet to the unity app. In one of my code chunk, I am trying to mint ERC 20 token by giving the Polygon Amoy Testnet currency. The transaction fails randomly. It gets successful like 4 in 10 times. I am unable to observe the test case because the error and success are random. The mobile wallet app crashes and in the logs I see JSON RPC error or gas estimate failed. I am using Reown App-kit and deployed my contracts on the polygon amoy testnet that has chainId eip:80002.

` await AppKit.InitializeAsync(new AppKitConfig { projectId = "your-project-id", metadataUrl = "https://metadata-url.com",

supportedChains = new[]
{
    ChainConstants.Chains.Polygon,

    new Chain(ChainConstants.Namespaces.Evm,
        chainReference: "80002",
        name: "Polygon Amoy",
        nativeCurrency: new Currency("Pol", "POL", 18),
        blockExplorer: new BlockExplorer("Oklink", "https://www.oklink.com/amoy"),
        rpcUrl: "https://rpc-amoy.polygon.technology",
        isTestnet: true,
        imageUrl: $"https://api.web3modal.com/public/getAssetImage/your-image-id",
        viemName: "polygonAmoyTestnet"
    )
}

});

`

here is the function hashes of the contract:

{ "dd62ed3e": "allowance(address,address)", "095ea7b3": "approve(address,uint256)", "70a08231": "balanceOf(address)", "313ce567": "decimals()", "4b94f50e": "getTokenPrice()", "40c10f19": "mint(address,uint256)", "06fdde03": "name()", "8da5cb5b": "owner()", "715018a6": "renounceOwnership()", "6a61e5fc": "setTokenPrice(uint256)", "95d89b41": "symbol()", "7ff9b596": "tokenPrice()", "18160ddd": "totalSupply()", "a9059cbb": "transfer(address,uint256)", "23b872dd": "transferFrom(address,address,uint256)", "f2fde38b": "transferOwnership(address)" }

Here is the code:

` // mint mr token using matics [ContextMenu("MintTokensWithMatic")] private async void MintTokensWithMatic() { // Get the user's account information Account account = await AppKit.GetAccountAsync(); string recipientAddress = account.Address;

    // Set the amount of MR tokens to mint (adjust this to the desired number of tokens)
    BigInteger mintAmount = new BigInteger(1e18); // Mint 1 MR token, scaled to 18 decimals

    // Hardcoded price: 1 MATIC per token
    BigInteger maticPricePerToken = new BigInteger(1e18); // 1 MATIC in wei

    // Calculate the total MATIC needed (1 MATIC per token)
    BigInteger totalMaticToSend = mintAmount * maticPricePerToken / new BigInteger(1e18); // Adjust for scaling

    // ABI encoding for "mint(address to, uint256 amount)"
    var functionSignature = "0x40c10f19";
    string recipientParam = recipientAddress.Substring(2).PadLeft(64, '0'); // Pad address to 32 bytes
    string amountParam = mintAmount.ToString("x").PadLeft(64, '0');         // Pad amount to 32 bytes

    // Concatenate function signature and parameters
    string data = functionSignature + recipientParam + amountParam;
    try
    {
        // Send the transaction to mint tokens, including 1 MATIC in wei
        var transactionHash = await AppKit.Evm.SendTransactionAsync(contractAddressMRToken, totalMaticToSend, data);

        Debug.Log("Mint transaction with 1 MATIC sent, transaction hash: " + transactionHash);
    }
    catch (Exception ex)
    {
        Debug.LogError("Failed to mint tokens: " + ex.Message);
    }
}

`

[skibitsky]

Hi!

You don't need to build data from the method signature manually. Instead you can call contract methods directly with the contract ABI. Docs with example: https://docs.reown.com/appkit/unity/core/usage#send-erc20-token

[Umair72Raza]

Now, I am getting this error

ReownNetworkException: Internal JSON-RPC error. Reown.Sign.Engine.Request[T,TR] (System.String topic, T data, System.String chainId, System.Nullable`1[T] expiry) (at ./mailto:library/packagecache/com.reown.sign@1.0.1/runtime/engine.cs:734) Reown.Sign.Nethereum.ReownSignServiceCore.SendTransactionAsyncCore (Nethereum.RPC.Eth.DTOs.TransactionInput transaction) (at ./mailto:library/packagecache/com.reown.sign.nethereum@1.0.1/runtime/reownsignservicecore.cs:55) .....

This is my updated code:

`

[ContextMenu("MintTokensWithMatic")] private async void MintTokensWithMatic() { // Get the user's account information Account account = await AppKit.GetAccountAsync(); string recipientAddress = account.Address;

    // Set the amount of MR tokens to mint (adjust this to the desired number of tokens)
    BigInteger mintAmount = new BigInteger(1e18); // Mint 1 MR token, scaled to 18 decimals

    // Hardcoded price: 1 MATIC per token
    BigInteger maticPricePerToken = new BigInteger(1e18); // 1 MATIC in wei

    // Calculate the total MATIC needed (1 MATIC per token)
    BigInteger totalMaticToSend = mintAmount * maticPricePerToken / new BigInteger(1e18); // Adjust for scaling

    // ABI encoding for "mint(address to, uint256 amount)"
    var functionSignature = "0x40c10f19";
    string recipientParam = recipientAddress.Substring(2).PadLeft(64, '0'); // Pad address to 32 bytes
    string amountParam = mintAmount.ToString("x").PadLeft(64, '0');         // Pad amount to 32 bytes

    // Concatenate function signature and parameters
    string data = functionSignature + recipientParam + amountParam;

    ////////////////////////////////////////////////////////////////////////

    BigInteger amount = new BigInteger(1e18);

    var arguments = new object[]
    {
        recipientAddress,
        totalMaticToSend
    };
    var result = await AppKit.Evm.WriteContractAsync(contractAddressMRToken, PayableMRTokenABI ,"mint",  amount ,arguments);
    Debug.Log("<color=yellow> Result </color>" + result);
    ////////////////////////////////////////////////////////////////////////
        }

`

[skibitsky]

Could you please share your contract ABI and address so I could take a look myself? 🙏

[Umair72Raza]

I have attached the files with abi and contract MRTokenABI.txt MRTokenContract.txt