Writing your first application

This guide will take you through the Sirius Chain development cycle. You will send your first transaction to the blockchain after combining some Sirius Chain built-in features.

Background Information

The secondary ticket market, also known as the resale market, is the exchange of tickets that happens between individuals after they have purchased a ticket from an initial vendor. The initial vendor could be the event website, an online ticket vending platform, a shop or a stall at the entrance of the event.

Buying a ticket from someone that is not the initial vendor does not necessarily only mean the buyer needs to pay more for the ticket. There is the chance that the buyer can become a victim of buying a fake or duplicate ticket, where the initial original vendor can’t do anything to solve the issue.

What do we want to solve?

Getting Started

Authorisation model

The ticket vendor wants to set up a system to:

  1. Identify each ticket buyer.

  2. Avoid ticket reselling.

  3. Avoid non-authentic tickets and duplicate ones.

Why should we use Sirius Chain?

Blockchain technology makes sense in cases where:

  • There are different participants involved.
  • These participants need to trust each other.
  • There is the need to keep track of an immutable set of events.

Sirius Chain is a flexible blockchain technology. Instead of uploading all the application logic into the blockchain, you can use its tested features through API calls for transfer and storage of value, authorization, traceability, and identification.

The rest of the code remains off-chain. This reduces the inherent immutability risk, as you could change the process when necessary.

Prerequisites

Getting into some code

Creating an account for each participant

First, we identify the actors involved in the problem we want to solve:

  • The ticket vendor.
  • The ticket buyer.

We have decided to represent the ticket vendor and buyer as separate accounts. Each account is unique and identified by an address. An account has access to a deposit box in the blockchain, which can be modified with an appropriate private key.

Have you loaded an account with test xpx? If it is not the case, go back to getting started section. The account you have created represents the ticket vendor.

  1. After running the following command, you should see on your screen a line similar to:
$> xpx2-cli account info


New Account: VCVG35-ZSPMYP-L2POZQ-JGSVEG-RYOJ3V-BNIU3U-N2E6

[...]

Mosaics

3628d0b327fb1dd8:       1000000
  1. This account owns 1,000,000 XPX. If your own mosaics is empty, follow the previous guide instructions.
  2. Create a second account to identify the ticket buyer.
$> xpx2-cli account generate --network TEST_NET --save --url http://localhost:3000 --profile buyer

Monitoring the blockchain

Accounts change the blockchain state through transactions. Once an account announces a transaction, if properly formed, the server will return an OK response.

Receiving an OK response does not mean the transaction is valid, as it may not be included in a block. A good practice is to monitor transactions before being announced.

We suggest opening three new terminals:

  1. The first terminal monitors announce transactions validation errors.
$> xpx2-cli monitor status
  1. Monitoring unconfirmed shows you which transactions have reached the network, but are not included in a block yet.
$> xpx2-cli monitor unconfirmed
  1. Once a transaction is included, you will see it under the confirmed terminal.
$> xpx2-cli monitor confirmed

Creating the ticket

We are representing the ticket as a mosaic. Mosaics can be used to represent any asset in the blockchain, such as objects, tickets, coupons, stock share representation, and even cryptocurrency. They have configurable properties, which are defined at the moment of their creation. For example, we opt to set transferable property to false. This means that the ticket buyer can only send back the ticket to the creator of the mosaic, avoiding the ticket reselling.

  1. Create a mosaic named ticket.
$> xpx2-cli transaction mosaic --mosaicname ticket--namespacename company--amount 1000000 --supplymutable --divisibility 0 --duration 1000
PropertyTypeDescription
Divisibility0The mosaic won’t be divisible, no one should be able to send “0.5 tickets”.
Duration1000The mosaic will be registered for 1000 blocks.
Initial supply1000000The number of tickets you are going to create
Supply mutabletrueThe mosaic supply can change at a later point.
TransferabilityfalseThe mosaic can be only transferred back to the mosaic creator.
  1. Copy the mosaicId returned in the monitor confirmed tab after the transaction gets confirmed.
...  MosaicId:7cdf3b117a3c40cc ...

Sending the ticket

Send one company:ticket to the ticket vendor account announcing a transfer transaction, one of the most commonly used actions in Sirius Chain.

  1. Prepare the transfer transaction. Three main attributes form a transfer transaction:
PropertyTypeDescription
Deadline1 HourThe maximum amount of time to include the transaction in the blockchain.
RecipientVC7A4H…2VBUThe recipient account address.
Mosaics[1 7cdf3b117a3c40cc]The array of mosaics to send.
Messageenjoy your ticketThe attached message.
NetworkTEST_NETThe local network identifier.
 
address, err := sdk.NewAddressFromRaw(os.Getenv("ADDRESS"))
if err != nil {
    panic(err)
}

mosaicId, err := sdk.NewMosaicId(srtconv.ParseUnit(os.Getenv("MOSAIC_ID"), 16, 64))
if err != nil {
    panic(err)
}

transferTransaction, err := client.NewTransferTransaction(
  sdk.NewDeadline(time.Hour),
  address,
  []*sdk.Mosaic{sdk.NewMosaic(mosaicId, 1)},
  sdk.NewPlainMessage("enjoy your ticket")
)
if err != nil {
    panic(err)
}
import {
    Account, Address, Deadline, UInt64, NetworkType, PlainMessage, TransferTransaction, Mosaic, MosaicId,
    TransactionHttp
} from 'tsjs-xpx-chain-sdk';

var mosaicId = new MosaicId("7CDF3B117A3C40CC");

const transferTransaction = TransferTransaction.create(
    Deadline.create(),
    Address.createFromRawAddress('VC7A4H-7CYCSH-4CP4XI-ZS4G2G-CDZ7JP-PR5FRG-2VBU'),
    [new Mosaic(mosaicId, UInt64.fromUint(1))],
    PlainMessage.create('enjoy your ticket'),
    NetworkType.TEST_NET
);
import io.proximax.sdk.model.account.Address;
import io.proximax.sdk.model.blockchain.NetworkType;
import io.proximax.sdk.model.mosaic.Mosaic;
import io.proximax.sdk.model.mosaic.MosaicId;
import io.proximax.sdk.model.transaction.Deadline;
import io.proximax.sdk.model.transaction.PlainMessage;
import io.proximax.sdk.model.transaction.TransferTransaction;

import java.math.BigInteger;
import java.util.Arrays;

import static java.time.temporal.ChronoUnit.HOURS;

BigInteger mosaicId = new MosaicId("7CDF3B117A3C40CC").getId();

final TransferTransaction transferTransaction = TransferTransaction.create(
    Deadline.create(2, HOURS),
    Address.createFromRawAddress("VC7A4H-7CYCSH-4CP4XI-ZS4G2G-CDZ7JP-PR5FRG-2VBU"),
    Arrays.asList(new Mosaic(mosaicId, BigInteger.valueOf(1))),
    PlainMessage.create("enjoy your ticket"),
    NetworkType.TEST_NET
);

Although the transaction is created, it has not been announced to the network yet.

  1. Sign the transaction with the ticket vendor account first, so that the network can verify the authenticity of the transaction.

Note

To make the transaction only valid for your network, include the first block generation hash. Open http://localhost:3000/block/1 in a new tab and copy the meta.generationHash value.

account, err := sdk.NewAccountFromPrivateKey(os.Getenv("PRIVATE_KEY"), networkType, generationHash)
if err != nil {
    panic(err)
}

signedTransaction, err := account.sign(transferTransaction)
if err != nil {
    panic(err)
}
const privateKey = "<private_key>";

const account = Account.createFromPrivateKey(privateKey, NetworkType.TEST_NET);

const signedTransaction = account.sign(transferTransaction, generationHash);
final String privateKey = "<private_key>";

final Account account = Account.createFromPrivateKey(privateKey, NetworkType.TEST_NET);

final SignedTransaction signedTransaction = account.sign(transferTransaction, generationHash);
  1. Once signed, announce the transaction to the network.

_, err = client.Transaction.Announce(context.Background(), signedTransaction)
if err != nil {
    panic(err)
}
const transactionHttp = new TransactionHttp('http://localhost:3000');

transactionHttp.announce(signedTransaction).subscribe(
    x => console.log(x),
    err => console.log(err)
);
final TransactionHttp transactionHttp = new TransactionHttp("http://localhost:3000");

transactionHttp.announceTransaction(signedTransaction).toFuture().get();
  1. When the transaction is confirmed, check that the ticket buyer has received the ticket.
$> xpx2-cli account info --profile buyer

What’s next?

Did you solve the proposed use case?

  • Identify each ticket buyer: Creating Sirius Chain accounts for each buyer.
  • Avoid ticket reselling: Creating a non-transferable mosaic.
  • Avoid non-authentic tickets and duplicate ones: Creating a unique mosaic named company.ticket.

Continue learning about more Sirius Chain built-in features.

← Setting up your workstationAccount →