How to pass multiple arguments in Remix? No matter which way I pass the arguments to the setOrder function, I get different errors: SyntaxError: Unexpected token in JSON at position 1 Error: ...

how display balance of token through Ethereum RPC? $id = 0; $data = array(); $data['jsonrpc'] = '2.0'; $data['id'] = $id++; $data['method'] = 'eth_call'; $data['params'] = [['from' => '0x0...',...

I am trying to deploy a contract from another factory contract and then return the address of the newly created contract. The address it returns however is the transaction hash not the contract add...

I am running a private Ethereum network. I do use https://aws.amazon.com/blockchain/templates/ The entire setup has been done. Things look setup properly on AWS. Now, I am trying to create the acc...

As I understand when using web3.eth.accounts.create(), it doesn't add the account to chain (I'm using ganache-cli for testing), but web3.eth.personal.newAccount() does. Is it the main purpose or i...

In the context of upgradable smart contracts, when should one use interfaces and when libraries? I read several similar questions and blog posts, but none of them give a straight-to-the-point answ...

I'm looking for a decentralized database for my Dapp. I found two helpful solutions orbitdb and gun but I couldn't realize the main difference and which one is more suitable for a social-media-lik...

I understand that RLPx is a protocol based on Kademlia DHT but one thing i'm not sure about is what's the need for this protocol or the problem that it is trying to solve ? Further it says it's o...

I could get the information about access another contract's variable from here But I couldn't find how to modify another contract's variable. Here is the example of contract A, contract A { ui...

Are there any limitation on the amount of arguments that can be send in an event? I have a function in which I want to trigger event that has 12 arguments of which 6 arguments are arrays. I get St...

When using the web3j lib for blockchain transaction in my private test blockchain I'm currently running into the titled response error: *insufficient funds for gas * price + value* The account fro...

I have a private parity node setup on my laptop. How can I make sure that there is 0 transaction fee whenever a transaction is posted in this private ethereum blockchain, meaning that I can post a ...

Below is my smart contract. When I put it in remix, I get warnings on each of the following functions. Gas requirement of function MedicalRecord.addNote(bytes32,bytes32) high: infinite. Gas requ...

I'm on Windows trying to connect to Ethereum Testnet via rinkeby. I downloaded geth 1.8.2 and Ethereum Wallet 0.9.3 I gave 1st command as: geth --rinkeby --fast --cache=1024 NOTE: after abov...

I need to make observable from window.web3.eth.getCoinbase((error, result) => { ... }); Is it a good idea? new Observable<string>(o => { this.w.eth.getCoinbase((err, result) =>...

I have been investigating different blockchains for some use cases. In the end, I came to the conclusion that setting up a private blockchain is equivalent to having a distributed database with blo...

I write Crowdsale using this example. But I can't send a transaction, my test fails with an error: Contract: Crowdsale should accept payments after start: AssertionError: expected promise to be...

pragma solidity ^0.4.15; import './ERC20.sol'; import './SafeMath.sol'; How connect SafeMath.sol from external(non-local) resourses?

I am using [email protected] to deploy smart contracts against a localhost:8545 [email protected] rpc, using an account that is funded with Ether has been unlocked using personal.unlockAc...

I can´t migrate the standart contracts that come with truffle compile. Here´s what i do: truffle init truffle compile open other terminal and run testrpc truffle migrate and the first three step...

Here it's a very high level description with only formulas. I want to understand actually how it works. I don't actually understand what a step is and what's it's use? Does a node always keep upd...

I am trying to subscribe to a PurchaseMade event defined in Solidty from the frontend. I am not getting the expected results and need help with what I'm doing wrong. Environment: ganache-cli, Tr...

The below code only returns a receipt but I want it to return a tuple of data, like in the contract below. How do I get it to return the data? I can't find a good tutorial on how to save and retrie...

How do I connect to a private network from ethereum wallet? I was able to create a private network from geth command line using custom genesis file but now wanted my ethereum wallet to point to cus...

How would I get the transaction cost inside of my contract? Would it just be: tx.gasprice ? And will this always be a value in gwei or will it be wei ?