All Questions

I want to write a smart contract that gets id numbers as inputs and then retrieve data that are recorded in a database.Is there any specific database for that process.

i have a doubt can i use an account created in metamask using nethereum? i tried this. var abi = @""; var addressContract = ""; var myAddress = "xxxxx"; var password = "password"; var managedAccount =...

I start a blockchain with ganache-cli, then I create a workspace in Ganache GUI the same seed phrase and port, but I keep getting this error in Ganache: I get and error this port is being used by ...

Recent code: pragma solidity ^0.5.11; pragma experimental ABIEncoderV2; contract Master { address Pi_C_Owner; address payable public NewAuctionPayable; //Hilfsvariable um ...

I am using a private network. I am trying to transfer network gas to another account, but I get this error: Returned error: Insufficient funds. The account you tried to send transaction from does not ...

I have been chacking around the site for possible solutions but i havent found any that would solve my (probably most basic) error. The account from which i'm sending has around 1 ether and i'm ...

I have created a node in quorum-maker using my ip address but that node is not starting.If i create a node using local ip(127.0.0.1), node starts.why?

When I call web3.eth.blockNumber from a specific full-node, where does it getting the last block? I know that the full-block holds part of the chain which he gets from gossiping with other full-nodes....

contract Evcharge { using Itmap for Itmap.AddressUintMap; event Transfer(address indexed _from, address indexed _to, uint256 _value); event Approval(address indexed _owner, address indexed ...

I build own ethereum private blockchain.Generating address and assign to users.Now how I will get the transaction info If user make payment from any third party api to our generated address then how I ...

i was trying to upload files to ipfs via nodejs. I want to upload file async without page refreshing. And receive hash on front and jquery Ajax --> nodejs--> ipfs. div class="input-group"> <...

How can I add mint and burn function to my erc20 contract code? This code is working properly but I couldn't add mint and burn function that work. Is there anyone who will help me about fixing this ...

I found this in the official solidity docs. The values of all members of msg, including msg.sender and msg.value can change for every external function call. This includes calls to library ...

Sorry, I'm a newbie on ERC721 token. Please help. I have deployed ERC721 contract in the localhost testnet. I use looping function for mint token and it works. But when I use looping function for ...

I was able to deploy to the contract and everything but I wanted to see another account interacting with the contract, but on Remix only one account at a time

I already built a smart contract for Ethereum Blockchain by using truffle to track the ownership of IoT devices; Now, I'm looking to connect my smart contract with the IoT environment (node) to detect ...

I already built a smart contract for Ethereum Blockchain by using truffle; Now, I'm looking to connect my smart contract with the IoT environment. So are there any IoT simulators (platform, framework,...

I use angular-truffle-box to create a dapp and when i tried to create a method getAge() and deploy the contract it shows me this error: Error: Returned error: {"id":12,"jsonrpc":"2.0","error":{"code":...

I tried to write a smart contract like the following. There are two function of a contract: the first function makes confirmation of a condition, the second function makes a new contract, if all ...

I am trying to verify an RSA signature using Ethereum smart contract. I have some doubts regarding my design. I am using the precompile at address 0X05 to generate s^e mod n, where s is the ...

Im trying to create my own new currency using solidity and ethereum platform and also i want to create an Ewallet of my currency using java so that my ewallet could communicate through api .If u ...

I would like to see what a PETH on Kovan is worth in DAI. How can you look for exchange rates on testnets?

how to put struct "s1" values in another variable. pragma solidity ^0.5.1; contract MyContract{ struct student{ int RollNo; string Name; } student public s1=student({...

I am using truffle console to deploy contracts and using Nodejs/web3js to interract with it. I wanted to use ethereumjs-tx for signing transaction, here is the reference link. I am not sure ,how can ...

After Istanbul fork, my full node followed the longest chain which has: Longest Chain Highest TotalDifficulty It seems that the shorter chain of the core-dev closing the gap - total difficulty ...

I am attempt to get an address using methods.call(). And it's something error. JS var rcAddr = "0x683d1602fa7252d49cda8ac414c1641a56e73d03"; var methodName = "Access Control"; var register = new ...

im trying to deploy smart contract on Myteherwallet but geting an error while deploying byte code of smart contact which is written in solidity remix IDE I have even tried to change the object byte ...

This is the problem I get when trying to run my contract! And then when I go ahead and run it, this pops up This is my js code: import React, { Component } from 'react'; import Web3 from 'web3'; ...

Sending ether from one address to another using web3js. Getting issue of "account unlock with HTTP access is forbidden"

please help me Module not found: Can't resolve 'web3' in 'C:\Users\block\src\components' i don'k know why .. my app.js import React, { Component } from 'react'; import logo from './logo.svg'; ...

In Bitcoin, historically, several ways to fork the network in have been used: User Activated Soft Fork (UASF): on a certain hardcoded blockchain height the nodes simply start enforcing the new rules ...

In my contact I want to have one place where I find an existing object(struct) and then use it in multiple places to read and modify it - but seems like it's not possible? contract A { struct ...

I sent a number of ERC20 tokens to Metamask. They are not showing in the MM wallet, but I do see them in Etherscan. I now want to sent them to a different address but I don't see how to do that. When ...

As documented in various places, the function selector is computed as the first four bytes of the keccak256 hash of the function header, which consists of the function name followed by the list of ...

My full node connected to 0,...,n peers and follows the longest chain after Istanbul fork - the miner's chain. General transaction flow: full-node get the tx, validates and broadcast to its peers. ...

In my truffle tests, I am trying to call a function from an account other than the default account, so not accounts[0] from the below result. web3.eth.defaultAccount doesn't seem to work. web3.eth....

i've mistakenly pasted "2.5" in address field submitted a withdrawal request. can i get my coins back since the address is an invalid or the coin will be sent? I'm afraid i may loose my coins.

I have a 3-node quorum setup that has been running from Jan 2019. The nodes were working without a problem until Sept 18 2019 when the network started to throw errors on submitting transactions with ...

When a contract calls a function in another contract, is the called function executed in the same EVM as the caller function, in another EVM on the same node or in another random node?

General info: We have a full-node, which broadcast our txs. We have a EventSource contract which contains 5 events types. The eventSource contract deployed only after Istanbul fork. Our node was ...

Can we send tokens with data input? I did a bit of research on erc20 but maybe this is quite complicated. Will erc 721 do this?

I'm building a Web3 app and I'm trying it out on the Kovan testnet. I'm trying to get some DAI. As far as I understand it the way to get DAI is to: Exchange ETH for WETH. Use Sai Tub contract to open ...

Where can one find the APR % fee when converting my Eth to Dai using the markerdao contract? And how is the fee paid in and when does it get paid?

I'm executing transactions on mainnet with a NodeJS script: async function send(web3, transaction, destAddr, gasPrice, privateKey) { const options = { data : transaction.encodeABI(), ...

During the previous fork on Ropstan, my node seems to follow to the wrong chain if I understood correctly. As for now, it's on 6537730, it's the longest but major players are around 6523511. What are ...

I've got a contract which creates another contracts and stores them in a list. How can I check that contract with specific index already exists? import "./User.sol"; contract Main is Ownable { ...

what is 'UnimplementedFeatureError: Not yet implemented - FixedPointType' error in solidity while compiling through truffle ? How to fix it ? Using solidity compiler version - 0.5.9

I am using a factory contract for selling and buying goods. how can retrieve how many buyers bought and calculate how much ether earned by selling goods? here is my source code. I am new on smart ...

When creating smart contract from scratch, what kind of things you should consider? For example: 1.Certain functions should be accessible only by creator/specific addresses 2.Fallback function Is ...

I'm new on Ethereum blockchain and I'm working on deploy and using smart contract using truffle on my private blockchain. I have followed exactly this guide https://www.trufflesuite.com/docs/...