All Questions

I want to get ETH for test with Kovan. I wrote my account in the Kovan Testnet/faucet. (https://gitter.im/kovan-testnet/faucet) It took around 3 hours, but I didn't get anything. (I checked metamask,...

If I have a contract that has a list of sellers, how would I code a simple contract that if some condition applies, the contract in an automatic way will increase the reputation/rating of the sender ??...

Just the main NFT contract for CryptoKitties, not the auction sale or other helper contracts. Bonus points if you can also include billable transactions that started from another contract and then ...

I am using web3js to send hundreds of transactions to Ropsten (will eventually change to mainnet) and I am getting a tx hash for all of them, which means that supposedly, all the transactions have ...

for address https://ropsten.etherscan.io/address/0x00916c608868c68f4cd8bea6786ab40b24b55392 balance is shoving 0 but from transactions it should be little more than one ether I believe there is ...

I'm fairly new to javascript and I'm trying to automate pulling the gas price from an api and using it into the truffle.js used to execute via truffle. Basically, I can pull the gasprice via the API ...

TL;DR - Replicated Ethereum Blockchain. Running Local Node. Connecting Local Node to Web3.js in browser using RPC. Want to create addresses & send transactions Details - I have a blockchain that ...

I receive an error when sending raw transactions. I get the following error message. Error: Returned error: Transaction nonce is too low. Try incrementing the nonce. I get my nonce this way: ...

I've seen interfaces in which the function definitions specify a return type, ie: (from openZepplin's IERC721.sol) function balanceOf(address owner) public view returns (uint256 balance); and ...

I'm listening to events of my deployed contract. Whenever a transaction gets completed and event is fired receiving the response causes following error: Uncaught Error: Returned values aren't valid,...

I'm trying to implement a simple card game. Actually, everything is working fine. Until I tried to move from 0.4.0 to 0.4.22. Any idea what is going wrong? Thanks a lot. And here the code: pragma ...

I have a function that fires an event at the end, I have more than one that works like this to create some kind of lifecycle through events. I get the full event history for every event as excpected,...

Isn't 0x0000000000000000000000000000000000000000 a burn address where no one has private key? If that is the case, how can this address send tokens to other addresses? If you look at Etherscan's ERC-...

I am trying to use ethminer in combination with Geth to solo mine with GPU, but ethminer fails to get work. Here is how I do. Geth is running in full sync mode and seems to be properly synchronized ...

So I modified the ERC20 token a little bit added two extra functions so that my ICO token contract can call it to send some tokens to the people. This is my erc20 token code. pragma solidity ^0.4.24;...

Let's say that I have created a token and this is distributed through a smart contract. Let's assume that this token is not on any exchange and whenever a transaction is executed using this token a ...

I have listed the versions of web3 versions installed in my system npm ls web3 inbox@1.0.0 /home/mdvenkatesh/Desktop/etherium solidity programes/inbox +-- truffle-hdwallet-provider@...

I am new to Blockapps. I am figuring out what is blockapp rest api? There github repo blockapp-rest In the repo the repository they referred were removed. My question is if I write the below code in ...

I have a question about the Metamask UI. Is it possible to set custom transaction method name for metamask history to make it more user-friendly? I want to rename "Bid" (default method name) to "Made ...

I am trying to read a mapping inside my smart contract that looks like this: mapping(address => User) public users; My web3js code looks like this. I am trying to read mapping users inside the ...

A while back I saw an example contract which allowed users to send any ERC-20 tokens through one of its functions, but I can't seem to find anything about this anywhere anymore. So, what is the ...

I have a contract with a function marked as onlyOwner (from OpenZeppelin, so only the address that deployed the contract can call it). pragma solidity ^0.4.17; import "./Ownable.sol"; contract ...

My contract is getting successfully deployed on the Rinkeby test network using truffle-hdwallet-provider but, the value I gave to the constructor (string a) while deployment is not getting initialized ...

A truffle test needs ethereumjs-wallet const wallet = require('ethereumjs-wallet'); I tried npm install ethereumjs-wallet and even npm uninstall ethereumjs-wallet npm install --save ethereumjs-...

If use gethcommand,then the node starts to sync with Ethereum Mainnet by default.If usegeth --testnet --networkid 3 --datadir <testnetdatapath>,then the node will connect to Ropsten. How does ...

Question: How to fix Fatal: Error starting protocol stack: Access is denied? Here is the steps that I try: geth --datadir block1 init /d/nodes/_ethereum/genesis.json geth --datadir block1 --...

I am trying to access a smart contract method through web3.js, but while a request, i am getting a following error in the console. web3.min.js:1 Failed to load https://rinkeby.infura.io/v3/...

I have private block chain on my PC.The private blockchain is configured and deployed using geth. I want to connect to that blockchain from another node(my laptop) to access the smart contract ...

Can anyone think of a clever way to re-set the IPC file permissions on a Parity re-start? I'm using systemd to control Parity.

Using trufffle-flattener, I am trying to create a flat file merging all the related solidity based codes. After executing the flattening scripts, I see only the empty flat file getting created. Could ...

When we use web3.eth.getPastLogs it returns topic and data properties together with rest data. Does it possible to retrieve event args parsing just data and topic as filter? Without to make additional ...

I developed with sql, mysql, ethereum mining kit, nodejs, ubuntu and I was trying to link a wallet to it somehow and I messed something up because they suspended my account due to "suspicious activity....

How do you calculate how much gas to use in a send_transaction? Amount: 0x670479cb5385800, // (decimal: 463949500000000000 wei 0.4639495 eth) Gas price: 0x6ddd00 // (decimal: 7200000 wei) Gas: ...

Say I want to make a smart contract that is able to save secret messages (strings). The messages should be stored only in encrypted form so no one can read them, but should be decrypt-able by a couple ...

I am trying to test a contract using truffle. My contract code is: pragma solidity ^0.4.22; contract MyContract5{ uint public mynumber; constructor ( ) public { mynumber = 24; } ...

I have a problem. we have an ico. I would like to use the selfdrop method for airdrop distribution. While the superskynet's ico continued, they also wrote a selfdrop contract. can you tell me how I ...

I have custom token code which extends the implementation of the standard ERC20 Token code. It has approveAndCall() function which sends token to another service contract code address. But I get the ...

Suppose i have contract like: pragma solidity ^0.4.11; contract MyToken { uint256 a; function SimpleGetter() returns(string) { return "something"; } function DoTheGreat(address _to) ...

Based on this question: What is the exact "longest chain" rule implemented in the Ethereum "Homestead" protocol? Is the situation still the same and uncles not counted for ...

I have a React component that implements a function to parse some public variables of a contract: getData() { const contract = require("truffle-contract"); const contractone = contract(...

I am new to Ethereum and wanted to clarify whether mining is possible if the graphics card has below the required amount of stated memory and it is part of a mining pool? I use ethminer and the ...

I'm trying to create 2d array of different types, one of the users have suggested to use struct within a struct method -> 2d array of different types? Now I run into problem how to display it in my ...

I am testing an ERC20 contract based on Openzeppelin-solidity template. But I am observing a curious behavior with reading a global variable. Here is the contract: pragma solidity ^0.4.24; import ".....

I am trying to obtain the pow-hash of a block. Is there a way of doing this easy? Thanks in advance :)

If i already have an ERC20 tokens created and has basic functionalities of a token sat at contract address A, can i start to develop a new smart contract which can make use of the ERC20 token at ...

Doing some ERC-735 tests on truffle+ganache I got stuck when creating claim signatures. They need to be signed from my ganache account, but I don't know its private key. The code to be used is this: ...

When trying the following code I will get an an wrong JSON RPC response. const fnc = myContract.methods.transferToken(...).encodeABI(); const tx = Object.assign({ nonce: nonce, ...

In order to demonstrate a contract, I want to use a generated UI, based on the ABI. The contract runs on local network, or on one of the testnets. Two options that I am aware of, and that work, but ...

Two contracts (code are for illustrative purposes only. Assume all syntax are correct): contract CA { function FA() public { // Invoke CB.FB() multiple times } } And contract CB ...

I am working on an application that stores and retrieves personal data on/from the ethereum blockchain. Just working on this to improve my Solidity and SC expertise and get comfortable with the ...