This document describes the process of deploying a smart contract using Remix and accessing it with Geth, the Go implementation of Ethereum. It details the steps necessary to set up a connection to a deployed contract via the contract address and ABI, and provides commands for interacting with the contract. The emphasis is on using Geth as a console for interacting with the deployed contract on a local TestRPC instance.

1. 6. Use Geth to Access a Deployed
Contract
KC Tam
Reach KC on LinkedIn: https://www.linkedin.com/in/ktam1/

2. Objective
In this section we deploy the contract using Remix, and use
Geth, a command line tool, to access it.

3. Geth (Go Ethereum)
Geth is the official Go implementation of Ethereum.
There are three implementations, using Go, Python and C++. Geth is by far the
most common.
A host running Geth becomes part of the Ethereum network (a node).
Besides, Geth also serves as a client and accesses Ethereum node.
● In this section we are using Geth client accessing a contract deployed on
TestRPC.

4. Ethereum Network (the Giant Computer)
Review: Access
Deployed Contract
Deployed contract can be accessed through
1. Contract Address and
2. Application Binary Interface (ABI)
Deployed Contract
Bytecode
ABI
Contract
Address
Web / Mobile Frontend
Contract AddressABI
Access

5. TestRPC on Localhost
Deploy the Contract
● Use Remix to deploy the SimpleStorage
contract
● Obtain the Contract Address
● By default, RPC opens on port 8545 on
TestRPC
Deployed Contract
Bytecode
ABI
Contract
Address
http://localhost:8545

6. First start TestRPC, and in Remix select Web3 Provider to interact with TestRPC.

7. Use Create to deploy the contract. Note that we see the Contract Address in both Remix and TestRPC.

8. Obtain ABI from Compile Panel on Remix.
ABI
[{"constant":true,"inputs":[],"name":"get","outputs":[{"name":"retVal","type":"uint
256"}],"payable":false,"stateMutability":"view","type":"function"},
{"constant":false,"inputs":[{"name":"x","type":"uint256"}],"name":"set","outputs":
[],"payable":false,"stateMutability":"nonpayable","type":"function"}]

9. TestRPC on Localhost
Access the Contract
● Run Geth client accessing RPC (port 8545)
● Define an object with ABI and Contract
Address
● Functions are executed through this object.
Deployed Contract
Bytecode
ABI
Contract
Address
geth
Contract AddressABI
Access
object
http://localhost:8545

10. Use another terminal and access TestRPC using RPC
$ geth attach http://localhost:8545
And we can check the 10 accounts on TestRPC
> eth.accounts

11. Keep <abi> into a variable abi.
> abi = <abi>

12. Define an object simpleStorage with abi defined above, and the contract address.
> simpleStorage = eth.contract(abi).at(<copied contract address>)
Now with simpleStorage object we can access variables and functions on this deployed contract.

13. To get the current value,
> simpleStorage.get()
To set a new value (note: we need to specify an account we use to execute the function.)
> simpleStorage.set(100, {from: eth.account[0]})
Note that this new value can also be seen in Remix

14. Summary
We use Geth as a console to access a deployed contract on
TestRPC. Both Remix and Geth access the same deployed
contract.