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Expanse Go

Official golang implementation of the Expanse protocol.

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Automated builds are available for stable releases and the unstable master branch. Binary archives are published at https://gexp.expanse.tech/downloads/.

Building the source

For prerequisites and detailed build instructions please read the Installation Instructions on the wiki.

Building gexp requires both a Go (version 1.9 or later) and a C compiler. You can install them using your favourite package manager. Once the dependencies are installed, run

make gexp

or, to build the full suite of utilities:

Executables

The go-expanse project comes with several wrappers/executables found in the cmd directory.

Running gexp

Going through all the possible command line flags is out of scope here (please consult our CLI Wiki page), but we've enumerated a few common parameter combos to get you up to speed quickly on how you can run your own Gexp instance.

Full node on the main Expanse network

By far the most common scenario is people wanting to simply interact with the Expanse network: create accounts; transfer funds; deploy and interact with contracts. For this particular use-case the user doesn't care about years-old historical data, so we can fast-sync quickly to the current state of the network. To do so:

$ gexp --fast --cache=512 console

This command will:

• Start gexp in fast sync mode (default, can be changed with the --syncmode flag), causing it to download more data in exchange for avoiding processing the entire history of the Expanse network, which is very CPU intensive.

• Start up gexp's built-in interactive JavaScript console, (via the trailing console subcommand) through which you can invoke all official web3 methods as well as Gexp's own management APIs. This tool is optional and if you leave it out you can always attach to an already running Gexp instance with gexp attach.

Full node on the Expanse test network

Transitioning towards developers, if you'd like to play around with creating Expanse contracts, you almost certainly would like to do that without any real money involved until you get the hang of the entire system. In other words, instead of attaching to the main network, you want to join the test network with your node, which is fully equivalent to the main network, but with play-Ether only.

$ gexp --testnet --fast --cache=512 console

The console subcommand has the exact same meaning as above and they are equally useful on the testnet too. Please see above for their explanations if you've skipped here.

Specifying the --testnet flag, however, will reconfigure your geth instance a bit:

Specifying the --testnet flag however will reconfigure your Gexp instance a bit:

• Instead of using the default data directory (~/.expanse on Linux for example), Gexp will nest itself one level deeper into a testnet subfolder (~/.expanse/testnet on Linux). Note, on OSX and Linux this also means that attaching to a running testnet node requires the use of a custom endpoint since gexp attach will try to attach to a production node endpoint by default. E.g. gexp attach/testnet/gexp.ipc. Windows users are not affected by this.

• Instead of connecting the main Expanse network, the client will connect to the test network, which uses different P2P bootnodes, different network IDs and genesis states.

Note: Although there are some internal protective measures to prevent transactions from crossing over between the main network and test network, you should make sure to always use separate accounts for play-money and real-money. Unless you manually move accounts, Gexp will by default correctly separate the two networks and will not make any accounts available between them.

Full node on the Rinkeby test network

The above test network is a cross client one based on the ethash proof-of-work consensus algorithm. As such, it has certain extra overhead and is more susceptible to reorganization attacks due to the network's low difficulty / security. Go Expanse also supports connecting to a proof-of-authority based test network called Rinkeby (operated by members of the community). This network is lighter, more secure, but is only supported by go-ethereum.

$ gexp --rinkeby console

Configuration

As an alternative to passing the numerous flags to the gexp binary, you can also pass a configuration file via:

$ gexp --config /path/to/your_config.toml

To get an idea how the file should look like you can use the dumpconfig subcommand to export your existing configuration:

$ gexp --your-favourite-flags dumpconfig

Note: This works only with gexp v1.6.0 and above.

Docker quick start

One of the quickest ways to get Expanse up and running on your machine is by using Docker:

docker run -d --name expanse-node -v /Users/alice/expanse:/root \
           -p 9656:9656 -p 42786:42786 \
           expanse/client-go --fast --cache=512

This will start gexp in fast sync mode with a DB memory allowance of 512MB just as the above command does. It will also create a persistent volume in your home directory for saving your blockchain as well as map the default ports. There is also an alpine tag available for a slim version of the image.

Pragmatically interfacing Gexp nodes

As a developer, sooner rather than later you'll want to start interacting with Gexp and the Expanse network via your own programs and not manually through the console. To aid this, Gexp has built in support for a JSON-RPC based APIs (standard APIs and Gexp specific APIs). These can be exposed via HTTP, WebSockets and IPC (unix sockets on unix based platroms, and named pipes on Windows).

The IPC interface is enabled by default and exposes all the APIs supported by Gexp, whereas the HTTP and WS interfaces need to manually be enabled and only expose a subset of APIs due to security reasons. These can be turned on/off and configured as you'd expect.

HTTP based JSON-RPC API options:

• --rpc Enable the HTTP-RPC server

• --rpcaddr HTTP-RPC server listening interface (default: "localhost")

• --rpcport HTTP-RPC server listening port (default: 9656)

• --rpcapi API's offered over the HTTP-RPC interface (default: "eth,net,web3")

• --rpccorsdomain Comma separated list of domains from which to accept cross origin requests (browser enforced)

• --ws Enable the WS-RPC server

• --wsaddr WS-RPC server listening interface (default: localhost)

• --wsport WS-RPC server listening port (default: 8546)

• --wsapi API's offered over the WS-RPC interface (default: eth,net,web3)

• --wsorigins Origins from which to accept websockets requests

• --ipcdisable Disable the IPC-RPC server

• --ipcapi API's offered over the IPC-RPC interface (default: admin,debug,eth,miner,net,personal,shh,txpool,web3)

• --ipcpath Filename for IPC socket/pipe within the datadir (explicit paths escape it)

You'll need to use your own programming environments' capabilities (libraries, tools, etc) to connect via HTTP, WS or IPC to a Gexp node configured with the above flags and you'll need to speak JSON-RPC on all transports. You can reuse the same connection for multiple requests!

Note: Please understand the security implications of opening up an HTTP/WS based transport before doing so! Hackers on the internet are actively trying to subvert Expanse nodes with exposed APIs! Further, all browser tabs can access locally running webservers, so malicious webpages could try to subvert locally available APIs!

Operating a private network

Maintaining your own private network is more involved as a lot of configurations taken for granted in the official networks need to be manually set up.

Defining the private genesis state

First, you'll need to create the genesis state of your networks, which all nodes need to be aware of and agree upon. This consists of a small JSON file (e.g. call it genesis.json):

{
  "config": {
    "chainId":  positive integer>,
    "homesteadBlock": 0,
    "eip150Block": 0,
    "eip155Block": 0,
    "eip158Block": 0,
    "byzantiumBlock": 0,
    "constantinopleBlock": 0,
    "petersburgBlock": 0
  },
  "alloc": {},
  "coinbase": "0x0000000000000000000000000000000000000000",
  "difficulty": "0x20000",
  "extraData": "",
  "gasLimit": "0x2fefd8",
  "nonce": "0x0000000000000042",
  "mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000",
  "parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
  "timestamp": "0x00"
}

The above fields should be fine for most purposes, although we'd recommend changing the nonce to some random value so you prevent unknown remote nodes from being able to connect to you. If you'd like to pre-fund some accounts for easier testing, create the accounts and populate the alloc field with their addresses.

"alloc": {
  "0x0000000000000000000000000000000000000001": {
    "balance": "111111111"
  },
  "0x0000000000000000000000000000000000000002": {
    "balance": "222222222"
  }
}

With the genesis state defined in the above JSON file, you'll need to initialize every Gexp node with it prior to starting it up to ensure all blockchain parameters are correctly set:

$ gexp init path/to/genesis.json

Creating the rendezvous point

With all nodes that you want to run initialized to the desired genesis state, you'll need to start a bootstrap node that others can use to find each other in your network and/or over the internet. The clean way is to configure and run a dedicated bootnode:

$ bootnode --genkey=boot.key
$ bootnode --nodekey=boot.key

With the bootnode online, it will display an enode URL that other nodes can use to connect to it and exchange peer information. Make sure to replace the displayed IP address information (most probably [::]) with your externally accessible IP to get the actual enode URL.

Note: You could also use a full fledged Gexp node as a bootnode, but it's the less recommended way.

Starting up your member nodes

With the bootnode operational and externally reachable (you can try telnet to ensure it's indeed reachable), start every subsequent Gexp node pointed to the bootnode for peer discovery via the --bootnodes flag. It will probably also be desirable to keep the data directory of your private network separated, so do also specify a custom --datadir flag.

$ gexp --datadir=path/to/custom/data/folder --bootnodes=

Note: Since your network will be completely cut off from the main and test networks, you'll also need to configure a miner to process transactions and create new blocks for you.

Running a private miner

Mining on the public Expanse network is a complex task as it's only feasible using GPUs, requiring an OpenCL or CUDA enabled ethminer instance. For information on such a setup, please consult the EtherMining subreddit and the Genoil miner repository.

In a private network setting however, a single CPU miner instance is more than enough for practical purposes as it can produce a stable stream of blocks at the correct intervals without needing heavy resources (consider running on a single thread, no need for multiple ones either). To start a Gexp instance for mining, run it with all your usual flags, extended by:

$ gexp  --mine --minerthreads=1 --etherbase=0x0000000000000000000000000000000000000000

Which will start mining blocks and transactions on a single CPU thread, crediting all proceedings to the account specified by --etherbase. You can further tune the mining by changing the default gas limit blocks converge to (--targetgaslimit) and the price transactions are accepted at (--gasprice).

Contribution

Thank you for considering to help out with the source code! We welcome contributions from anyone on the internet, and are grateful for even the smallest of fixes!

If you'd like to contribute to go-expanse, please fork, fix, commit and send a pull request for the maintainers to review and merge into the main code base. If you wish to submit more complex changes though, please check up with the core devs first on our gitter channel to ensure those changes are in line with the general philosophy of the project and/or get some early feedback which can make both your efforts much lighter as well as our review and merge procedures quick and simple.

Please make sure your contributions adhere to our coding guidelines:

• Code must adhere to the official Go formatting guidelines (i.e. uses gofmt).

• Code must be documented adhering to the official Go commentary guidelines.

• Pull requests need to be based on and opened against the master branch.

• Commit messages should be prefixed with the package(s) they modify.

  • E.g. "eth, rpc: make trace configs optional"

Please see the Developers' Guide for more details on configuring your environment, managing project dependencies and testing procedures.

License

The go-expanse library (i.e. all code outside of the cmd directory) is licensed under the GNU Lesser General Public License v3.0, also included in our repository in the COPYING.LESSER file.

The go-expanse binaries (i.e. all code inside of the cmd directory) is licensed under the GNU General Public License v3.0, also included in our repository in the COPYING file.