Linked Questions

140
votes
2answers
26k views

What is the difference between a transaction and a call?

What is the difference between a transaction and a call? In some interfaces, I can interact with contracts via calls or via transactions. What is the difference between the two, and can contracts also ...
84
votes
2answers
48k views

Which cryptographic hash function does Ethereum use?

Many sources refer to the use of the "SHA3" cryptographic hash function within Ethereum, but the Ethereum project began before the SHA3 standard was finalised, and there was some confusion/controversy ...
21
votes
2answers
15k views

How do I know how much gas to use when calling a contract?

When I am calling (sending a transaction to) a contract how do I determine how much gas to use? Is there a way to calculate this upfront & what happens if I send too much / too few gas?
13
votes
3answers
10k views

Is it possible to build a private (permissioned) blockchain with Ethereum?

Ethereum is a great blockchain, but for some services the transaction fee is prohibitively too expensive. Is there any project and/or guideline on making Ethereum so it works on permissioned ...
10
votes
2answers
697 views

Why does Ethereum have gas?

Why does Ethereum have gas? What other approaches could Ethereum have used to work around the Halting Problem?
8
votes
1answer
967 views

Can a transaction get lost?

Given that I am connected to the network with at least one peer, can I be sure that a transaction I sent will be executed (either with fail or success)? Is there a possibility that it will never make ...
7
votes
2answers
2k views

Who gets the fee from contract call?

Basically you don't need to pay fee for contract call, but if a contract method does lots of work, you need to add gas in contract call to prevent DoS attack like this: contract.method.call({gas: ...
5
votes
1answer
952 views

What's the difference in the ways of calling a contract function?

After I get an instance of a contract, there are 3 ways to call the contract function below: 1.testInstance.testfunc({from:eth.accounts[0]}) 2.testInstance.testfunc.sendTransaction({from:eth.accounts[...
4
votes
3answers
85 views

Can a “forward” smart contract forward the received ether to another “forward” smart contract which forwards it to an address?

I am pretty new to solidity. I am trying to create a smart contract which deploys another smart contract and transfers ether to the newly created contract when a payment greater than 0.01 ether is ...
4
votes
2answers
134 views

Call Smart Contract every 5 Second

Is it possible the call a method of a smart contract every 5 seconds? Lets say i want to call a webservice or an other smart contract in order to get the actual value? That is not possible or? In ...
4
votes
1answer
4k views

How to Set Gas Price in Private Blockchain?

I admit that I don't understand Gas at all. But I think it is basically the currency which dapps use to interact with each other and the blockchain. Yes? If you're creating a custom/private network,...
4
votes
1answer
2k views

Where exactly do DApps run? Who gets rewarded for running them? [duplicate]

So I am currently running a full node, as well as a GPU miner. I am curious first of all where do DApps get run? They wouldn't make sense to run on a GPU as they aren't very parallizable, so I am ...
3
votes
3answers
4k views

What is the point of variable transaction fees in Ethereum (and Bitcoin as well)?

After reading through the docs and through this post, I understand the concept and need for gas, but I do not understand why each transaction can have a variable fee associated with it. It seems to be ...
3
votes
1answer
593 views

what is difference between “gas” “gas price” and “fee”?

Can we say that gas is the unit of transaction fee ? And gas price is the same transaction fee ? If so, why we do not use ether and wei instead of gas ?
3
votes
1answer
1k views

When calling a smart contract function, who gets paid and how much does the caller pay?

This is an extended question to What is "gas" and transaction fee in Ethereum?. Who gets paid and how much does the caller pay? Let's make some assumptions: There is a function F which ...

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