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I have setup a local private test net and now I want to connect from Node.js to a node in the testned using IPC. I started a node with this command: ./geth --identity "5" --datadir /home/davide/...

WinCon.sol EnemyCon.sol To create interaction, I am creating interface for EnemyCon in WinCon.sol, but Remix is throwing compilation error stating "EnemyCon should be marked abstract". I ...

I'm trying to have a simple array of integer sorted in Solidity but i couldn't find any real ressources so instead i'm trying to do it "the hard way" but so far with very little success. Is anyone ...

our project now uses scheduled task to query the eth address with infura API to get its balance every 10 seconds but as the number of addresses keep increasing, the efficiency is very bad. Is there ...

My question may be stupid. I'm trying to understand how ethereum is made and in all articles I read that a block header include a list of things and the stateRoot, the transactionsRoot and the ...

I am trying to withdraw a contracts balance to the owner of that contracts account. It works perfectly on the JVM in solidity browser. But on TestRPC it has an out of gas exception. The account has a ...

I am using Web3 1.3.0. Connecting using Node. Also if I try to enter the name of my Event I get an error saying that event does not exist. This is what I get, shouldn't event have a value ? I am using ...

gyp WARN install got an error, rolling back install gyp WARN install got an error, rolling back install gyp ERR! configure error gyp ERR! stack Error: EACCES: permission denied, mkdir '/usr/lib/...

I created a simple smart contract using OpenZeppelin and deployed the contract to the Kovan testnet. However, when I send KEth to the contract using MetaMask, nothing happens (I believe the buyTokens ...

Many of you might think that this question has already been answered but I don't think that there is a clear answer on the internet for the current Ethereum, Web3.js and React Native versions (for ...

I'm currently trying to set the token price of my ERC-20 token.The problem I'm having is trying to set the price to ETH(0.01) per token, but the closest value I keep getting to is ETH(0.001) per token ...

After building from Quorum source, I can see Swarm as on the binaries. How can one get Swarm to work alongside Quorum?

Unable to verify my contract on etherscan. This is the link - https://ropsten.etherscan.io/address/0xc68c67a1864060631817be1eebdb91e8661fae7a . Please help. Its urgent. Here is my code: pragma ...

I’m receiving then ex error: C:\Users\xxxxx\AppData\Roaming\npm\node_modules\truffle\build\commands.bundled.js:455204 throw new Error("Could not find artifacts for " + import_path + " ...

I've been using truffle console to interact with a contract which I developed locally with Ganache. I'd like to be able to call the contract's methods using the console once deployed to the Rinkeby ...

If I were to fork my private Proof of Authority chain can I revert without pruning a block with corrupted data and subsequently all successor blocks which do have complete data and if so how can I ...

I had created 100 million tokens and created a contract for crowdsale in test network If user sends a 1 ether using contract address i am able to receive 1 ether and send 1000 tokens to user who send ...

I have a problem running npm run dev when I create a crowd sale project reference yt: Dapp University this my app.js code: App = { web3Provider: null, contracts: {}, account: '0x0', loading: ...

I want to implement an ERC-1155 contract. Using TDD we would first write a test. Which begs the question of is there a way to validate that your contract properly implements ERC-1155?

I have the following struct inside my vyper file: races: public({ start: timestamp, end: timestamp, racersBetHash: bytes32[address], racersBetAmount: wei_value[address] }[int128]) Then I ...

I want to preview a major revision of my Dwebsite before I update the IPFS CID to which the mainnet ENS name resolves; this requires locally resolvable names so hyperlinks and resource references work ...

I have a constructor like so: constructor(bytes32[] proposalNames) public { ... How do I input values for it on deplyoment with remix? I tried ["foo", "bar"] but it said: ...

I'm trying to simulate a transaction on the public blockchain that invokes a contract's method with certain parameters. Then I want to make a follow-up transaction with some other method call. I ...

Do we have any standardized security scanning tool to go for security code review for solidity language? If not, what all opensource tools are there on which we can relay? Need response urgently.

I have this code to show the erc20 token balance of an account var tokenAddress = '0xb97E9bBB6fd49865709d3F1576e8506ad640a13B'; var walletAddress = '0x62f28320f688A7A4e0021c55d7ffD1acd770A133'; ...

This is the contract I am calling from: contract MultiTransfer { function multiTransfer(Marcelo token, address _addresses, uint256 amount) public { token.transfer(_addresses, ...

I have this contract and I've deployed it to ganache pragma solidity >= 0.5.0; contract HelloWorld { string public payload; function setPayload(string memory content) public { ...

Why people wrap 'now' in _now() function that just returns 'now'? Found that on xDAI contracts: function _now() internal view returns (uint256) { return now; } Is it because in 0.7.0 'now' was ...

I know how a private smart contract works providing a list of accepted addreses to privateFor property, but what if I want to disable (or enable) any address visibility? Should I deploy a new Smart ...

I am trying to send ether from an account to my smart contract to another account through a function in my smart contract but I am receiving the error: "Transaction has been reverted by the EVM: {...

I am stuck with a weird situation. I create a local Ethereum network with Hyperledger Besu in docker environment. I try to deploy contracts to a rpc node using Truffle(different container in same ...

Let's say I want to have higher order function capabilities in my Solidity Dapp. Also I want to be able to pass in new functions as input to higher order functions contained within contracts that were ...

1)For this purpose, would like to build a SDK that can be integrated with my existing mobile app. 2)I have around 5million Downloads-users that would use this SDK. a)The User data would want to pass ...

I've been able to decode the inputs to a contract function transaction given the ABI as follows: var myFunction = contract.GetFunction("MyFunction"); var myFunctionTxn = await contract.Eth....

Is there any way that i could run a shell script after a contract is deployed,since the terminal has geth Javascript console running,and there are some commands which are already in the shell script. ...

I want to build an electronic device. This device can be a raspberry pi with a ledger USB device, or anything else. This device will need to call an Ethereum smart contract. For example let's suppose ...

I made ERC20 token. And I am going to implement to send token using web3.py. Here I want to calculate gas price and gas limit using token transaction. If anyone know about that, please help me. ...

When I was coding the unitary tests for my smart contract on Remix, I encountered a problem of gas limit: contract deployment failed after trying twice: The contract code couldn't be stored, please ...

I am developing a simple Voting dApp by following a tutorial. In this tutorial we are using npm install ethereumjs-testrpc web3 so that we can get the fake nodes of Ethereum. For that i first ...

The Spadina testnet launched less than 2 days ago. What is the purpose of the Zinken testnet? What is being covered that was not covered in Spadina? Related: What are the Ethereum 2.0 testnets?

I have read several differences between fungible and non fungible tokens. It cleared my few doubts though, I have few more remaining. I have requirement to create a platform on which users can ...

I have a smart contract deployed on the Testnet here - https://ropsten.etherscan.io/address/0xD99ea28F24317F28291556754edd24AA1352c26e This contract has a public function triggerAgeCount function ...

https://github.com/enjin/erc-1155/blob/master/contracts/ERC1155.sol says something about "operator approval". What is an operator and what is operator approval?

Developing an ERC1155 contract, how to generate an address for a new token? I need to create an API function like function createToken() returns (address). How? Should I just use an incrementing-by-...

New ERC1155 standard which is thought to be an improved version of ERC721 and ERC20. But I see many projects still prefer ERC20 or ERC721 standards. If so, do you know any projects implementing ...

I have created an NFT and now I want to add some metadata e.g card images, that shows in a compatible wallet like trust wallet. What step is needed next?

I want to check if a user had registered in my DAPP with Metamask..Do I need to store User struct in solidity to control that or just depend on metamask for authentication.??

I try to interact with Ethereum node via web3 lib. (meteor add ethereum:web3) Meteor 1.5.4.1 lib.js if (typeof web3 === ‘undefined’){ web3 = new Web3(new Web3.providers.HttpProvider(‘http://127.0.0....

I'm trying to create a contract factory that creates "Oracles". Oracles have state variables that are initialized in the contract constructor, and I'm trying to use Truffle Test to verify ...

This question will be very similar to this one, but I'm stuck and don't know what to do: Token contract source code not verified Anyways, my friend sent me 2 pieces of code, the actual contract code,...