All Questions

I really need help with this one to avoid logic errors. I am on the Kovan testnet. I bought 4 units of DAI token on Uniswap exchange(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D) for 0.111 Ether and ...

I have a private key. I need to cancel a pending transaction sent from its address. How to do this from command line? Also: I need to do the exactly same thing if there are several such pending ...

my purpose is to generate a random key when the smart contract is created and save that key in a private variable. I don't what to know its value either. Let's take for example the code below: pragma ...

The project is a group of Ethereum users, who wants to send their data to the blockchain network to be saved, this data is sent by these users by Python. My question, how is this data sent by users, ...

My computer is a dream machine with 64gb RAM and 28 cores operating at 4-5Ghz. Using Linux Mint. I also have a fairly modern Nvidia graphiques karrd with 8gb VRAM. I am mining XMR on 24 of my 28 cores,...

I am attempting to keep a log of when a user does certain things but when a new log event is reached the second log is overwritten instead of adding a new one to the array I am unsure as to why when ...

I have a function where I am trying to compare the values of 2 mappings. However, I am receiving an invalid opcode error. Which has me confuzzled because I already set the values of both the mappings ...

How can I calculate percentage of a number in solidity? say I want to calculate 95% of the number 200. How should I go about doing that ?

I was running debug_traceTransaction on the transactions in the first 100,000 blocks, and I came across 25 that were flagged as failed, but etherscan.io says they are fine. The gas used is below gas, ...

when I use stanfordnlp for Arabic language I keep having this errors ..\aten\src\ATen\native\BinaryOps.cpp:81: UserWarning: Integer division of tensors using div or / is deprecated, and in a future ...

i'm new to solidity and i'm developing an easy app. This is the contract i'm working on. It's all functioning but i need to: do some sort of function that return me all the array value whit the same ...

If you were writing some instructions and one of them was: Provide the Ethereum ECDSA signature of the file using the person's Ethereum address. Would the above instruction have a consistent meaning ...

I was running a full node GETH client for main net Ethereum in a server. The server crashed and was shut for around 8 hours. But after fixing the server and running the full node the GETH doesnt run. ...

I ran debug_traceTransaction on tx "0x7faf48b09018e507c49c1c44b139fa05c262fb1e3425a43ae80e6c9ccb3fcf0e" (block 1805546, txindex 1: contract creation), and I received back a massive 157MB ...

We are creating a system where every month some ethers shall be transferred from user wallet to a contract wallet. We are focusing on creating a dapp too, so a user will initiate this request and once ...

Can ERC-20 based stablecoins be confiscated or blacklisted? Can I lose my stablecoins? What are differences between stablecoins out there?

When running my chain my gas limit drops drastically from the set limit of the genesis block "gasLimit": "0x3B9AC9FF" due to large gaps both in time and frequency between the ...

Converting a file to a byte array to be stored as bytes[] in solidity I am able to convert the file using the following function, but when I send it to my smart contract I get error "TypeError: ...

I believe one of the main criticisms of chainlink is that it is not decentralized enough, adding more nodes would be a big step in a positive direction. When I pull data through a node, that node ...

I access Ethereum from several wallets. Some of the addresses are present in several wallets at once. I discovered that nonces should always increase. (Right?) Then if I send transactions from several ...

I have a geth node running on a linux machine, and have set up a firewall (UFW) to allow all outgoing connections, but inbound connections to 30303/udp and 30303/tcp only. I'm noticing in my system ...

I am writing a simple betting application that will return double the ether deposited by the player, provided they guess correctly the random number generated by the virtual slot machine. it works ...

I am an student and in this moment practicing how to create a simple smart contract in remix.ethereum.org. I got compiled the small program with function get without problem. When I deploy the program ...

I just have started to learn Smart Contract. I have to design front end in ASP.NET. Can I call Contract from it?

I want to create a crypto currency (ERC20 token) with truffle or solidity. Basically, i want to sell digital product that can cost as example 10$. I want to convert that 10$ into my currency (ERC20 ...

Let's suppose there is a contract address A of an erc721 token B. If I want to monitor all of its transfers from A to another address say C then should I only filter the Transfer function or should I ...

My understanding is that if a smart contract consumes a library that only has internal functions, then the compiler will embed the library into the contract bytecode. At the lowest level, there is no ...

when I try to send my transaction using infura I get this error "The send transactions "from" field must be defined" My problem is my web3 object. When I used Metamask and ...

Will i need a front end framework like React, while using web3 to build Decentralized Applications?

I'm working with private blockchain, and facing some issue with SSL configuration. The system has two components: The private blockchain that is configured on the VM. The web application that ...

My friend said to me that he has his seed saved in Google Drive and that he is absolutely safe even if someone found it out. He even gave me his seed to try to break it. I know that all I have to do ...

I'm trying to implement something like this (which works) function withdraw() public { msg.sender.transfer(address(this).balance) } but I need to be able to withdraw ERC20 tokens other than ...

After reading some topics on the implementation of ZK methods in the Ethereum, how would this affect the PoW? Please have someone correct me if I am wrong (I started recently), but if the nodes need ...

I can connect to web3. I am able to send ETH to another account using truffle develop and the sent ETH shows on my metamask account. I have installed truffle-hdWalletProvider as well Whenever I use ...

Why the usual way to create a contract with evm opcodes use add and mload, for example: bytes memory bytecode = hex"600580600c6000396000b800602a600052b8"; ... assembly { _address := ...

TL;DR: wanted: a method that receives an address as a parameter and returns an array of token names/contracts/balances held by address. I'm aware of the fact that Etherscan API has a method allowing ...

I am new to ethereum and curious about interacting with dApps while keeping a private key in cold storage. I like the idea of keeping the private key for an Ethereum wallet on an air-gapped computer. ...

I call a function with the transaction like this https://ropsten.etherscan.io/tx/0x7d4dec3c0db2b700efae63ef3ffb5a33fc2335bd992fd37c48aa10560eb8156e this fuction is a call from other contract,I wrote ...

I want to know how to deploy Smart Contract on Ethereum 2 Testnet using web3 ?

I use OpenEthereum(v3.0.0) on warp sync. OS is ubuntu server 20.04. But its snapshot syncing is proceeding but block number is still zero(#0). Please see the following image. Is this proper condition?...

When I start a transaction, MetaMask shows it with Cancel button. When does this Cancel button disappear? Maybe after one confirmation? After N (what is N?) confirmations?

I have a local ethereum node and I am trying to filter an event for a contract address between a range of blocks. However it throws the following error: node:15689) UnhandledPromiseRejectionWarning: ...

pragma solidity ^0.5.13; contract WorkingWithVariables { uint256 public myUint function setMyUint(uint_myUint) public { myUint = _myUint; } bool public mybool; ...

I make a contract method call using .send() method: contractInstance.methods.pay(itemId).send({from: defaultAccount, value: web3.utils.toWei(String(price*1.0000001)), gas: '1000000'}, ...

I am using following appoach How to deploy Ethereum Smart Contract through Brownie to the Private Network. I want to automate this process in order to capture the transaction hash and deployed ...

How do I migrate full node from PARITY to GETH ? So the easy part to tun geth I know, but How do i move all the keys from parity to geth? I've tried to copy the keystore folder from parity to geth, ...

I have a function marked as payable in contract A and I want to call it from contract B so that msg.value in contract A can have its desired value and contract A must have balance of sent amount , how ...

i have a Transaction Hash: 0x9f46760404dd3075533e8360fe4beb0ba7210423af1f4a95a5c80defffe824b5, for how do i decode the "input data" easily? for example: https://www.blockchain.com/eth/tx/...

I am doing arbitration with some measure of success; but I suspect I am running into edge cases where the available reserve size is less than what I am trying to buy or sell. Something like this: ...

I tried this method to deploy a contract. It is described in the web3.eth.Contract documentation. var contract = new web3.eth.Contract (JSON.parse (abi_json_string)); contract.deploy ({ data: ...