All Questions

2
votes
1answer
38 views

How to pay gas fee for new addresses of ERC20 tokens that initially have 0 Eth balance? [duplicate]

I have a confusion, When we create new address/account for an ERC20 token then it have 0 Eth balance. When we send some tokens to this address and then withdraw token again from this address require a ...
1
vote
0answers
30 views

Trying and failing to switch my dapp from local node to infura, please help? [closed]

I have a nodejs 'server' running that listens for events on the blockchain. Currently I have this line in my code: var provider = new Web3.providers.HttpProvider("http://localhost:8545"); But I'm ...
1
vote
1answer
19 views

Is it possible to connect to public Ethereum like blockchain with Remix to deploy and view contracts?

I've tried to do so by specifying the web3 provider and the 8584 port but it gets stuck on every try. Is this possible? if so, is there another solution for that need?
1
vote
1answer
24 views

Issue Deploying Contract LinkedIn Course - Ethereum: Building Blockchain Decentralized Apps (DApps)

I'm completely new to Ethereum Smart Contracts. I'm following the course on LinkedIn [Ethereum: Building Blockchain Decentralized Apps (DApps)]. I've been able to compile the smart contract as per ...
1
vote
0answers
17 views

Private Etherum to work like Main Net

I want my private Ethereum blockchain to work like the Main net, I want to fix the number of mined ether (Set Max Cap over minded ether), and don't want that miners earn by mining empty blocks.
1
vote
1answer
25 views

How do i create account remotely?

I have two servers, one for eth-node, one for web api and user db. I want to send request to create account from web server to eth server, but i see it can be created by running command like geth ...
1
vote
1answer
41 views

Solidity Error Address / Address Payable

I'm currently learning solidity programming to create a basic smart contract based on a 2018 tutorial where solidity was using version 4. I'm currently using truffle v5.0.21. I understand that there ...
1
vote
1answer
35 views

web3 - Contract deployment has been reverted by the EVM

I want to deploy a contract but my transaction gets reverted. This only happens with Web3, while it works fine with Remix.I can assure the ABI and Bytecode are correct because I pasted them from Remix,...
1
vote
1answer
35 views

web3 unlock account error

I have two geth nodes, each has an account: node1(IP:192.168.43.12): account1 node2(IP:192.168.43.39): account2 the two accounts are created using geth --datadir /root/chain/node1/data account new, ...
1
vote
1answer
25 views

Newbie. Getting cannot read property 'abi' of undefined when trying to deploy on Ubuntu

let abi = compiled.contracts.example.PartyTime.abi; This is the line of code that is causing the error. I copied the abi code from Remix into an abi.json file. But it doesn't seem to be reading it ...
1
vote
0answers
19 views

How to create ethereum wallet with multiple node? [closed]

How to to create ethereum wallet with multiple peers for single node? Need to create private ethereum network with 1 node & it's 2 peers. Each node should have 2 accounts.
1
vote
0answers
9 views

Nodes from private network don't gossip

I have three Ethereum nodes created with Geth. Two of them are on my machine (MacOS) and the third one is running on a virtual machine with Ubuntu. Because I used the same genesis.json and also the ...
1
vote
1answer
36 views

Smart Contract is being deployed but call does not return contract address after deployment

So I have been trying to deploy a smart contract using nodejs, but when I call the function to deploy, I get no contract address on my console. It's like the send() function never completed its ...
2
votes
0answers
32 views

How the following pairing equality be verified in Etherum Smart contracts?

I have found available precompiled contracts in solidity. For example, this answer enter link description here points out a precompiled contract that can verify BLS signature. However, looking to the ...
1
vote
1answer
14 views

Detection of var vulnerability: problem with search string

SmartCheck tool at: SmartChek: Static Analysis of Ethereum Smart Contracts suggests detection of 'var' key word in the smart contract by searching the assignment statement such that the Left Hand Side ...
1
vote
1answer
11 views

Was testing this code I found online but keep getting errors?

pragma solidity ^0.5.0; contract Courses { struct Instructor { uint age; string fName; string lName; } mapping (address => Instructor) instructors; address[] public instructorAccts; ...
0
votes
0answers
22 views

Drizzle Installation: pauses at fetchMetadata: sill resolveWithNewModule http-https@1.0

I am following this tutorial https://www.trufflesuite.com/tutorials/getting-started-with-drizzle-and-react. Everything is working smoothly until I have to npm install drizzle. I then run into the ...
2
votes
2answers
17 views

What is the latest implementation of approveAndCall() - Solidity ˆ0.5.0

Just curious for some background on approveAndCall() 1) Is it initially an ERC223 method ? or is it officially part of the ERC20 interface ? 2) Also Im working with an old contract so Im wondering ...
1
vote
1answer
15 views

Error in Declaring a Sized Array: Generating no gas Exception

I have created a fixed size array: pragma solidity ^0.5.1; contract Underflow1 { uint8 arr[256]; uint8 i= 0; function testf2() public returns (uint8){ for(i=0; i<arr.length; ++i);...
1
vote
1answer
20 views

I've given Gwei less than 0.1 for a transaction, and it's been an hour, and it is not showing up in etherscan!

I know I pretty much messed up with Gwei, I've given it < 0.1. My doubt is if the transaction gets failed will the funds get back to my wallet or lost forever and how much time will it take for the ...
1
vote
1answer
18 views

Private Blockchain

Suppose I create my own private blockchain using Ethereum over the public network means my node is reachable from the internet, now I don't want to share my genesis.json but still want that other can ...
1
vote
0answers
29 views

Using web3j with infura returns null

I've used web3.js to handle my contracts, and it worked very well. But web3j is pretty hard for me since the beginning. I'm using android studio, infura, web3j. Since I don't know very much about ...
1
vote
1answer
40 views

After EIP 198 introduction, how much gas is required for RSA signature verification in solidity?

Thanks to the introduction of EIP 198, RSA signature verification is now feasible in Ethereum. How much gas is required for such a verification?
3
votes
1answer
26 views

Compilation error using SafeMath

I am trying to do subtraction operation using the SafeMath library. The following is my code: pragma solidity ^0.5.1; library SafeMath { function sub(uint256 a, uint256 b) internal pure returns (...
1
vote
1answer
22 views

Infura event listening [duplicate]

I am using Infura, Ropsten Test network, Web3@0.20 in the back-end of my Express website. I want to listen events in my ERC20 contract. I tried a lot of methods, but still failed. How do I revise it? ...
4
votes
1answer
31 views

Timestamp in Ethereum

I have a smart contract where the user inputs temperature readings, I'd like to add a time stamp to relate those reading with a current time of submission. I understand that in Ethereum we only have ...
1
vote
2answers
43 views

Storage/Retrieval of mapped structure data

I want to store the structure data in a mapping i.e. if I have a student structure as described below, then I should be able to have a myriad of students and distinguish between them using wallet ...
1
vote
0answers
13 views

Problem connecting web3 via websocket to node with nginx

we are trying to connect to a geth node via WebSockets to be able to subscribe to contract events. This node is created with docker and this docker uses nginx as a proxy. We can connect easily with ...
0
votes
1answer
15 views

Why do my events not emit the correct value?

When testing a contract with Truffle, I have found that the variables that are emitted by the event do not match the values that are passed into the event emission. Why does the event not return the ...
0
votes
1answer
31 views

a smart contract deploying another one

I am working on a crowdfundin dapp and I have a problem while deploying a smart contract from another one. Actually , the main smart contract called crowdFactory is supposed to invoke a smart ...
0
votes
1answer
27 views

Web3 connecting to Infura

installed web3 and follwed steps int he image
0
votes
1answer
13 views

Deploy contract to Parity dev chain using Remix

I'm trying to deploy a contract via remix to my local development chain. However, the transaction never gets mined and is pending forever. When I use a node script it works (at least I receive the ...
0
votes
0answers
37 views

“Method not found” when trying to parity_subscribe to eth_getFilterChanges

Parity Ethereum version: 2.5.1-beta, tested on 2.4.6 as well Operating system: Linux (Ubuntu) Installation: binary Fully synchronized: yes Network: ethereum Restarted: yes I'm using a websocket. I ...
0
votes
1answer
12 views

connecting geth to web3.go 1.0 via websockets or HTTP

Is there anyThing similar to web3.js written in go that allows me to communicate with the geth client ?
0
votes
2answers
36 views

Operator & not compatible with types bytes32 and int_const

i have the code below: uint256 lastBlockNumber = block.number - 1; bytes32 hashVal = bytes32(block.blockhash(lastBlockNumber)); bytes5 _byteData = bytes5((hashVal & 0xffffffff) <&...
0
votes
0answers
13 views

Connection dropped by Kaleido websocket

Connecting to Kaleido with websockets and listening on contract events works fine, but after some time (even if constantly receiving events) the connection is dropped by Kaleido. The problem appears ...
1
vote
1answer
24 views

Error encoding arguments: SyntaxError: Unexpected token e in JSON at position 2 while string concatenation

I am just adding 2 strings into one string but getting below error: transact to TestStrings.testCOntract errored: Error encoding arguments: SyntaxError: Unexpected token e in JSON at position 2 ...
0
votes
1answer
17 views

Same genesis for private network?

I have initialized one private node using geth and Genesis file, and now I want to span another node, in genesis file, I have mentioned on the account which will be pre-funded now I want Ans of below ...
0
votes
1answer
32 views

How to test the fuctionality of a Bittrex-related smart contract?

I've got my hands on a smart contract related to the Bittrex exchange. I would like to deploy this smart contract to test the functionality but I don't know how to call the functions properly. My ...
1
vote
1answer
28 views

Dates of ERC20 tokens transactions

I'm an individual who is interested to ICOs which are selling ERC20 tokens. My question is related to an issue that, for most of the ERC20 tokens, the dates of transactions do not fall within the ICO ...
1
vote
0answers
27 views

Solidity: TypeError: Member “unbond” not unique after argument-dependent lookup in contract super EthGatedMarket

I'm getting this error: TypeError: Member "unbond" not unique after argument-dependent lookup in contract super EthGatedMarket. super.unbond(msg.sender, gatewaySpecifier, quantity); ^----------...
1
vote
1answer
23 views

Calling a smart contract function with an unsigned transaction

I'm new to working with Ethereum smart contracts and would appreciate some guidance by the community on a task that I'm trying to solve. This is the contract I want to use - https://github.com/chatch/...
2
votes
0answers
25 views

Suck at JavaScript and overall just a beginner in the dev world. Whats the best way to begin building DApps? [closed]

Suck at JavaScript and overall just a beginner in the dev world. Whats the best way to begin building DApps? The title is my question LOL.
1
vote
1answer
18 views

Developer downloading ledger reasoning? [duplicate]

My question is a little odd, but I will ask it anyways. From a development perspective, knowing that there is a service such as Infura, why would a developer download the whole ledger? Infura ...
2
votes
0answers
34 views

Simple mixer in ethereum

I have found this mixer proposal https://hackmd.io/@HWeNw8hNRimMm2m2GH56Cw/rJj9hEJTN?type=view I'm is interested in this topic, but from my point of view with a current ethereum state it won't work. ...
3
votes
1answer
23 views

Matrix multiplication in solidity

I am trying to implement an algorithm requiring matrix multiplication. I know I can program this in the rudimentary way similar to doing the process by hand, but I am worried about the computational ...
0
votes
0answers
39 views

cannot unmarshal hex string of odd length into Go value of type hexutil.Bytes?

const Tx = require('ethereumjs-tx').Transaction; const Web3 = require('web3'); const web3 = new Web3('https://ropsten.infura.io/161d7c8443f14babb3c176023628a055'); // console.log(web3.eth.accounts....
0
votes
1answer
27 views

How can I parse internal transactions with light node?

is that possible to receive all transactions from new block with light node and parse all and even internal transactions with the help of its api?
4
votes
2answers
207 views

Offchain vs Sidechain vs StateChannel

What are the main differences between off-chain, sidechain and state channel? And what are the use-cases of all of these?
1
vote
0answers
10 views

DApp BPMN architecture design [closed]

I want to design my dApp on Ethereum but i want to explain the application logic (smart contracts) through BPMN to explicit my decentralized exchange.. Can someone help to design my decentralized ...

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