Questions tagged [blockchain]

The Ethereum blockchain is a distributed database based on the Ethereum whitepaper specification and stores both the full transaction list and the most recent state.

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How to concatenate an address to a string in solidity

I am trying to find the correct way to concatenate an Ethereum address to a string in Solidity v0.6.7 I tried the following but it did not seem to work : function append(string a, address b) ...
0 votes
1 answer
12 views

Error when attempting to send SepoliaETH between two accounts in remix via smart contract with specific conditions: Cause of error -->undefined gas

I would like to use my smart contract to map a payment transaction from SepoliaETH from one Metamask account to another Metamask account. The conditions of a transaction limit and a recall function of ...
1 vote
3 answers
700 views

Why is Transaction Value showing 0 ETH on Etherscan?

I'm not sure why the transaction value on Etherscan is showing as 0 ETH when the transaction was confirmed. According to the recipient, they haven't received anything in their wallet either and I'm ...
1 vote
2 answers
625 views

Smart Contract - Update implementation using a Relay with delegateCall

I know that smart contracts are supposed to be immutable and that's the whole point, but to expect someone to implement a logic that never changes (no upgrade or no bugs) from day 1 is also ...
0 votes
1 answer
2k views

Can't connect to localhost:8545 while using ethereumjs-testrpc web3?

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 ...
0 votes
0 answers
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Swapping/Cashing out?

I want to start out by saying I know nothing about this kind of stuff. But, my husband and I have Ethereum in some wallet and has been trying to "cash out" (not sure if this term is correct) ...
0 votes
0 answers
11 views

Transaction reverted: function returned an unexpected amount of data when requesting Institution Data

I am trying to request for Institution details which returns two or more data but getting these error. Error: Transaction reverted: function returned an unexpected amount of data at Institution....
0 votes
0 answers
52 views

Error: contract runner does not support sending transactions (operation="sendTransaction", code=UNSUPPORTED_OPERATION, version=6.11.1) [duplicate]

Error: contract runner does not support sending transactions (operation="sendTransaction", code=UNSUPPORTED_OPERATION, version=6.11.1) i got this error what should i do ?
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1 answer
18 views

Cannot able to deploy contract having parameter

I am trying to deploy Certification.sol in my unit test but it's giving me error. TypeError: unsupported addressable value (argument="target", value={ "args": [ "...
0 votes
1 answer
307 views

Throughput and Latency of Private Ethereum Network

How do I calculate Throughput and Latency of a private Ethereum network that I have set up locally on my computer? I tried the solution given in Measuring transaction latency and throughput in a multi ...
0 votes
1 answer
389 views

ERROR processing when testing the contract - TypeError: Cannot read property 'length' of undefined

I am getting the following error while trying to test a FundMe contract. I am following: Learn Blockchain, Solidity, and Full Stack Web3 Development with JavaScript – 32-Hour Course by Patrick ...
1 vote
1 answer
573 views

What is the formula for calculating Ethereum block size in megabytes?

I know that the Ethereum block size is bounded by gas limit, But I need to know the size in megabytes. There is a chart in YChart That represents block size in bytes, But they say: "there's not a ...
2 votes
2 answers
431 views

why does it matter to sync nodes with time?

As we know, time gets set on a block's header as the miner's current local time. Each node while accepting a block, checks if the new block's time is more than parent 's time and is not also in the ...
1 vote
1 answer
17 views

Getting error when trying to get Transaction Events Logs

I am trying to check whether an event is emitted or not in my unit test. But getting error as length undefined. The error I am getting is TypeError: Cannot read properties of undefined (reading '0') ...
0 votes
0 answers
9 views

Geth Blockchain synchronised issue

i am developing my private Blockchain using geth. I am created successfully my private Blockchain and created native coin on that, after that I created RPC URL for metamask later I am transfer some ...
1 vote
2 answers
589 views

I got an Error in Encrypting the Private Key using ethers

const ethers = require ("ethers") const fs = require ("fs-extra") require ("dotenv").config() async function main () { const wallet = new ethers.Wallet(process.env....
0 votes
0 answers
9 views

Is it possible for a view function to revert (in a loop?)

If I have a view function and it runs a loop to get a large set of data, is it possible to revert and be out of gas, or no matter how big the loop is will it still call it? This function will not be ...
0 votes
0 answers
10 views

How does the Sepolia Test Network work?

How do Test Nets like Sepolia stay in operation? According to chat GPT hosting a node has no token or financial award so why do people do it? In that case how are people supplying free faucets if ...
0 votes
0 answers
9 views

Can I use a faucet for my application

I am implementing the blockchain into the web app to track user's work with one another and plan to have tokens within the smart contract to exchange with one another. The user who deploys the ...
1 vote
1 answer
25 views

What is the metamask algorithm for creating accounts based on one seed phrase?

Metamask uses one seed phrase to generate other accounts. Thus, with one seed phrase you can restore all accounts. But what is the algorithm for this? I want a script that could show 10 of my accounts ...
0 votes
1 answer
353 views

contract.methods.payFund is not a function. Unable to call any of my contract function

I am unable to call any function of my contact.............. when I am printing my contract object it shows that all the functions are in the object but unable to call. It is the output when i print ...
0 votes
0 answers
11 views

Could not transact with/call contract function, is contract deployed correctly and chain synced [closed]

# from medilcal import contract_abi,contract_bytecode from web3 import Web3, HTTPProvider import web3 import json from eth_account import Account from web3.contract import Contract import json from ...
0 votes
1 answer
15 views

Not able to run a function of a smart contract (Create Community) from Express.js server

I am trying to create community from express server but getting an error. The get Community is running fine I am able to get the Community corresponding to that particular id. But when trying to send ...
0 votes
2 answers
534 views

How can I insert values from web browser Firefox or chrome like html and js to ethereum blockchain?

How to save values from an HTML form into block chain through a browser, I have gone through different tutorials, but it is confusing, how this go-ethereum blockchain and smart contract can access ...
1 vote
0 answers
21 views

How do users avoid paying gas fees?

I have this web app implemented in React typescript where users can create posts and in return for fulfilling these posts, they gain credits from the other users. These credits are stored on the ...
0 votes
0 answers
28 views

Flash loan. Been hacked twice [closed]

I'm just frustrated with this. I tried twice with aave. The flash loan arbitrage bot, and each time it will come down to sending my profits to my wallet.??? It never happens. The funds go straight to ...
0 votes
1 answer
671 views

Restore from ethereum keystore file results in an unusable private key

I have a keystore file from an old ellipal wallet with some eth with it. The corresponding password is correct (I can use it to display the private key and keystore in it) and I can also run the ...
0 votes
2 answers
2k views

signing a transaction on web3js with private key and broadcasting to nodes

I am having an issue with ethereum based project. I made web3 API to communicate to the blockchain. I did this two ways. both call the same function on same address: METHOD 1 (Using Unlocked ...
0 votes
1 answer
898 views

Geth solo mining with trex possible? - General questions / Job handling on different mining tools

i'm pretty new to this topic but like to learn how things are working. I got some general questions to the different miner-settings available. First of all i know about pool-mining and how to set it ...
0 votes
2 answers
35 views

How do I give each user a private address for transactions

I have a web app in React Typescript with supabase as a database. I want to integrate the blockchain with it in order to track work done between users. How would I give each user an private address ...
2 votes
1 answer
697 views

How to change block generation period?in POA private ethereum blockchain

my genesis.json like that: "config": { "chainId": 333, "homesteadBlock": 1, "eip150Block": 2, "eip150Hash": "0x0000000000000000000000000000000000000000000000000000000000000000", "...
0 votes
1 answer
554 views

ParserError: Identifier-start is not allowed at end of a number. 0x0

I am migrating the following smart contract to local Blockchain (Ganache). however when I run migrate it's giving me an error: ParserError: Identifier-start is not allowed at end of a number.0X0 how ...
5 votes
4 answers
6k views

Problem In Getting Rinkeby Test Ethers

I tried to get rinkeby ethers from https://faucet.rinkeby.io/ by creating a tweet but the website shows "insufficient funds for gas * price + value” error. I also tried the website faucets....
0 votes
1 answer
1k views

How do i import my ethereum wallet just using private key?

Help me out how do i resolve the issue of ethereum smartcontract for getting my wallet when i enter my private key in the text area Use WalletUtils functionality The WalletUtils class can be used to ...
0 votes
1 answer
2k views

How get estimated gas before sending the transaction?

How do you get the "estimated gas" from a "swapExactETHForTokens" function? As shown in metamask (before one can accept the purchase) Binance Smart Chain (BSC) From the pancakeswap ...
0 votes
2 answers
2k views

Does the gas fee increase, when variable (a mapping type) in my smart contract is getting bigger

In my smart contract, I have the following property struct MyStruct { uint256 property1; uint256 property2; } mapping(address => MyStruct) private structs; In one function, this struct is ...
0 votes
1 answer
2k views

Code:const web3 = new Web3(window.web3.currentProvider) Error: window.web3 is undefined

I am going to connect my contract with the website.However,there was something wrong with the web3? I'm not sure. import Web3 from "web3"; const web3 = new Web3(window.web3.currentProvider); const ...
0 votes
1 answer
307 views

How to obtain blocks information easily?

I am interested in collecting blocks' information in Ethereum. For example, for each block i want to get the followings: Gas Limit, Used Gas, Gas Price, Tx fee, Number of tx, number of uncles. I am ...
0 votes
1 answer
771 views

How to validate a transaction from any block in Blockchain

Given that we have a Blockchain with smart contracts. We have end users operating the platform for some time. Now one user wants to verify the claim of a transaction. Example, I have to prove that ...
1 vote
1 answer
132 views

How do I fix Error: Deployment Failed on ganache?

I am encountering this error while deploying my smart contract on the Ganache blockchain, can anyone help me fix it? Error: *** Deployment Failed *** "Coffee" hit an invalid opcode while ...
0 votes
1 answer
679 views

How ERC20 Token balance are recovered during Ethereum chain rolling-back

My Answer: Ok, the problem is really with Ganache ... If I use geth, everything is alright. ... ... sorry for your time ... ---------------- The Original Question -------------------- My ...
0 votes
1 answer
496 views

Where does geth store data except for the AppData\Roaming\Ethereum folder?

The AppData\Roaming\Ethereum folder on my computer weighs 5GB, but geth has reduced my disk space by a lot more than 5GB. Where else does it store data?
1 vote
0 answers
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Deployment is getting stuck in Raffle contract

I am not able to deploy Raffle contract as it is getting stuck. Here is image of the error. It is not completing only. Here is my Raffle contract // SPDX-License-Identifier: MIT pragma solidity ^0.8....
0 votes
2 answers
2k views

Can I get price feed information directly from ChainLink oracles rather than from the aggregated contract?

I've been experimenting with ChainLink recently and am fascinated of what it can do. I already used the code provided here ChainLink Docs in Python and got it to work. However, I've been searching all ...
0 votes
1 answer
184 views

Error with Withdrawing Ethereum into Account

I am attempting to withdraw ETH from my smart contract that I have deployed using Solidity in Remix. I have already deposited 0.001 ETH into the smart contract using MetaMask and wish to use the ...
0 votes
2 answers
763 views

Developing a Staking and Un-staking Smart Contract

I am relatively new to blockchain, and trying to write a staking smart contract, which could stake any ERC20 token and gives APY in the same token with the following requirements: Staking of ERC20 ...
0 votes
2 answers
395 views

Unable to use unlockAccount() in web3

i am trying to unlock a account using unlockAccount() from personal module but i am getting an error const Web3 = require("web3"); const Personal = require("web3-eth-personal"); ...
0 votes
1 answer
307 views

Error while running web3 instance

I have a 2 node Ethereum system already setup. I am trying to have a web3 client talking to it. I installed web3 on a client machine and it gave no errors. However, I try to setup index.js and do ...
0 votes
1 answer
326 views

Connecting To Multiple Wallets Simultaneously To Dapp On The Frontend

I'm exploring the possibility of building a Dapp that enables the user to connect multiple wallets simultaneously. The reason is that for my particular use case, the NFT category that I'm observing ...
0 votes
1 answer
90 views

Geth transactions not broadcast and stuck in pending state

Setup three Geth private network nodes(Clique) via docker container. They are deployed on three different VMs. Among 3 nodes, there is a miner node to mine the block, a RPC node to accept RPC request, ...

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