Ethereum Nodes – Types and Their Functions

Disclaimer: I run ethernodes.org

There is a node explorer available at ethernodes.org which tries to estimate the number of nodes on the Ethereum network.

The estimation is based on an active crawling process that recursively connects to a node and asks for its known peers. As this approach only reaches nodes that are accessible from the outside a second, passive approach is used to reach nodes behind a NAT.

An 'Ethereum client' is just a term. It refers to any node able to parse and verify the blockchain, its smart contracts and everything related. It also allows you/provides interfaces to create transactions and mine blocks which is the key for any blockchain interaction.

Official reference implementations (CLI)

There are currently three reference implementations available, as you already highlighted:

• Aleth - C++ client: https://github.com/ethereum/aleth. (It was formerly known as cpp-ethereum: https://github.com/ethereum/webthree-umbrella)
• Geth - Golang client of the go-ethereum project: https://github.com/ethereum/go-ethereum
• Trinity - Python client: https://github.com/ethereum/trinity

All clients should work the same, from the user's perspective. They provide the same interfaces and so on. For example, if you launch a DApp or the Ethereum Wallet or a DApp browser instance, it should not note any difference in communicating with the client.

Third party implementations (CLI)

Non-official clients implementing the yellow paper specification are:

• Besu - (ex-Pantheon) Java client by PegaSys: https://github.com/hyperledger/besu
• EthereumJ - Java client by the ether.camp team: https://github.com/ethereum/ethereumj
• EthereumJS VM - Javascript Ethereum Virtual Machine: https://github.com/ethereumjs/ethereumjs-vm
• Mana - Elixir by POA Network - https://github.com/mana-ethereum/mana
• Minimal - Go client by umbracle - https://github.com/umbracle/minimal
• Nethermind - C# / .NET by Nethermind
• Parity Ethereum - Rust client by Parity Technologies : https://www.parity.io/ethereum/

Third party implementations (GUI)

Non-official clients with a graphical user interface are:

• Etherwall, a Qt client like the good ol' bitcoin clients: https://github.com/almindor/etherwall

Deprecated or abandoned projects:

Official reference implementations (CLI):

• Pyethapp - (pyethapp has been deprecated) Python client of the pyethereum project: https://github.com/ethereum/pyethapp

Graphical clients:

• AlethZero (Alethzero has been deprecated): https://github.com/ethereum/alethzero
• Mist Browser (Mist and Ethereum Wallet have been deprecated): https://github.com/ethereum/mist

Third Party clients:

• ethereumH - Haskell client from consensys, but it's not developed anymore: https://github.com/jamshidh/ethereum-client-haskell (project has not been updated in a long time)
• node-blockchain-server - simple Javascript server: https://github.com/ethereumjs/node-blockchain-server (project has not been updated in a long time)
• ruby-ethereum - Ruby client: https://github.com/janx/ruby-ethereum (project has not been updated in a long time)

NOTE: all clients are listed in alphabetical order.