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Skycoin Exchange Integration

A Skycoin node offers a REST API on port 6420 (when running from source; if you are using the releases downloaded from the website, the port is randomized)

A CLI tool is provided in cmd/skycoin-cli/skycoin-cli.go. This tool communicates over the REST API.

The API interfaces do not support authentication or encryption so they should only be used over localhost.

If your application is written in Go, you can use these client libraries to interface with the node:

Note: The CLI interface will be deprecated and replaced with a better one in the future.

The wallet APIs in the REST API operate on wallets loaded from and saved to ~/.skycoin/wallets. Use the CLI tool to perform seed generation and transaction signing outside of the Skycoin node.

The Skycoin node's wallet APIs can be enabled from the command line. -enable-all-api-sets will enable all of the APIs which includes the wallet APIs, or for more control it can specified in a list of API sets, e.g. -enable-api-sets=READ,STATUS,WALLET. See the REST API for information on API sets.

For a node used to support another application, it is recommended to use the REST API for blockchain queries and disable the wallet APIs, and to use the CLI tool for wallet operations (seed and address generation, transaction signing).

Running the skycoin node

For integrations, the skycoin node should be run from source with ./run-daemon.sh. This requires go1.10+ to be installed.

API Documentation

Wallet REST API

Wallet REST API.

Skycoin command line interface

CLI command API.

Skycoin REST API Client Documentation

Skycoin REST API Client

Skycoin Go Library Documentation

Skycoin Godoc

libskycoin Documentation

libskycoin provides a C library for Skycoin's cryptographic operations. This allows python, ruby, C#, Java, etc applications to perform operations such as transaction signing and address verification, without using the Skycoin daemon API or calling the CLI tool from the shell.

libskycoin documentation

Implementation guidelines

Scanning deposits

There are multiple approaches to scanning for deposits, depending on your implementation.

One option is to watch for incoming blocks and check them for deposits made to a list of known deposit addresses. Another option is to check the unspent outputs for a list of known deposit addresses.

Using the CLI

To scan the blockchain, use skycoin-cli lastBlocks or skycoin-cli blocks. These will return block data as JSON and new unspent outputs sent to an address can be detected.

To check address outputs, use skycoin-cli addressOutputs. If you only want the balance, you can use skycoin-cli addressBalance.

Using the REST API

To scan the blockchain, call GET /api/v1/last_blocks?num= or GET /api/v1/blocks?start=&end=. There will return block data as JSON and new unspent outputs sent to an address can be detected.

To check address outputs, call GET /api/v1/outputs?addrs=. If you only want the balance, you can call GET /api/v1/balance?addrs=.

Using skycoin as a library in a Go application

We recommend using the Skycoin REST API Client.

Sending coins

General principles

After each spend, wait for the transaction to confirm before trying to spend again.

For higher throughput, combine multiple spends into one transaction.

Skycoin uses "coin hours" to ratelimit transactions. The total number of coinhours in a transaction's outputs must be 50% or less than the number of coinhours in a transaction's inputs, or else the transaction is invalid and will not be accepted. A transaction must have at least 1 input with at least 1 coin hour. Sending too many transactions in quick succession will use up all available coinhours. Coinhours are earned at a rate of 1 coinhour per coin per hour, calculated per second. This means that 3600 coins will earn 1 coinhour per second. However, coinhours are only updated when a new block is published to the blockchain. New blocks are published every 10 seconds, but only if there are pending transactions in the network.

To avoid running out of coinhours in situations where the application may frequently send, the sender should batch sends into a single transaction and send them on a 30 second to 1 minute interval.

There are other strategies to minimize the likelihood of running out of coinhours, such as splitting up balances into many unspent outputs and having a large balance which generates coinhours quickly.

Using the CLI

When sending coins from the CLI tool, a wallet file local to the caller is used. The CLI tool allows you to specify the wallet file on disk to use for operations.

See CLI command API for documentation of the CLI interface.

To perform a send, the preferred method follows these steps in a loop:

  • skycoin-cli createRawTransaction $WALLET_FILE -m '[{"addr:"$addr1,"coins:"$coins1"}, ...] - -m flag is send-to-many
  • skycoin-cli broadcastTransaction - returns txid
  • skycoin-cli transaction $txid - repeat this command until "status" is "confirmed"

That is, create a raw transaction, broadcast it, and wait for it to confirm.

Using the REST API

The wallet APIs must be enabled with -enable-api-sets=WALLET,READ.

Create a transaction with POST /wallet/transaction, then inject it to the network with POST /injectTransaction.

When using POST /wallet/transaction, a wallet file local to the skycoin node is used. The wallet file is specified by wallet ID, and all wallet files are in the configured data directory (which is $HOME/.skycoin/wallets by default).

Using skycoin as a library in a Go application

If your application is written in Go, you can interface with the CLI library directly, see Skycoin CLI Godoc.

A REST API client is also available: Skycoin REST API Client Godoc.

Coinhours

Transaction fees in skycoin is paid in coinhours and is currently set to 50%, every transaction created burns 50% of the total coinhours in all the input unspents.

You need a minimum of 1 of coinhour to create a transaction.

Coinhours are generated at a rate of 1 coinsecond per second which are then converted to coinhours, 1 coinhour = 3600 coinseconds.

Note: Coinhours don't have decimals and only show up in whole numbers.

REST API

When using the REST API, the coin hours sent to the destination and change can be controlled. The 50% burn fee is still required.

See the POST /wallet/transaction documentation for more information on how to control the coin hours.

We recommend sending at least 1 coin hour to each destination, otherwise the receiver will have to wait for another coin hour to accumulate before they can make another transaction.

CLI

When using the CLI the amount of coinhours sent to the receiver is capped to the number of coins they receive with a minimum of 1 coinhour for transactions with <1 skycoin being sent.

The coinhours left after burning 50% and sending to receivers are sent to the change address.

For eg. If an address has 10 skycoins and 50 coinhours and only 1 unspent. If we send 5 skycoins to another address then that address will receive 5 skycoins and 5 coinhours, 26 coinhours will be burned. The sending address will be left with 5 skycoins and 19 coinhours which will then be sent to the change address.

Verifying addresses

Using the CLI

skycoin-cli verifyAddress $addr

Using the REST API

Not directly supported, but API calls that have an address argument will return 400 Bad Request if they receive an invalid address.

Using skycoin as a library in a Go application

https://godoc.org/github.com/skycoin/skycoin/src/cipher#DecodeBase58Address

if _, err := cipher.DecodeBase58Address(address); err != nil {
    fmt.Println("Invalid address:", err)
    return
}

Using skycoin as a library in other applications

Address validation is available through a C wrapper, libskycoin.

See the libskycoin documentation for usage instructions.

Checking Skycoin node connections

Using the CLI

Not implemented

Using the REST API

  • GET /api/v1/network/connections

Using skycoin as a library in a Go application

Use the Skycoin REST API Client

Checking Skycoin node status

Using the CLI

skycoin-cli status

Using the REST API

A method similar to skycoin-cli status is not implemented, but these endpoints can be used:

  • GET /api/v1/health
  • GET /api/v1/version
  • GET /api/v1/blockchain/metadata
  • GET /api/v1/blockchain/progress

Using skycoin as a library in a Go application

Use the Skycoin CLI package

xpub wallets

You can create a wallet from an xpub key, which allows you to generate new addresses without exposing secret keys. You can use any xpub key from an existing Bitcoin or Ethereum HD wallet you may already have, or you can create a new HD wallet in Skycoin.

To create an xpub wallet from scratch:

  1. Create a bip44 wallet
  2. Export an xpub key from the bip44 wallet
  3. Create the xpub wallet

If you already have an xpub key, you can skip to step 3.

Create a bip44 HD wallet

Using the CLI

skycoin-cli bip44-wallet.wlt -t bip44

Using the REST API

  • POST /api/v1/wallet/create

Export an xpub key from a bip44 wallet

Using the CLI

skycoin-cli walletKeyExport bip44-wallet.wlt -k xpub --path "0/0"

Using the REST API

Not possible

Create an xpub wallet

Using the CLI

skycoin-cli walletCreate xpub-wallet.wlt -t xpub --xpub $MY_XPUB_KEY

Using the REST API

  • POST /api/v1/wallet/create