fabric-samples/fabtoken

FabToken Sample Application

This is a Node.js sample application that demonstrates how to perform token operations on a Fabric network using Fabric Node SDK.

The sample assumes an understanding of the Hyperledger Fabric network (orderers, peers, and channels) and of Node.js application development, including the use of the Javascript promise, async and await.

For more information about tokens on Hyperledger Fabric, see Using Fabtoken

For more information about the Fabric SDK for Node.js, refer to Node SDK documentation

For more information about the Node SDK TokenClient API, refer to the following:

• TokenClient API reference
• FabToken tutorial

Run the sample

You can find the fabtoken.js sample application in the javascript directory. We will use this application to create and transfer tokens on a network created using the basic-network sample. First, we need to some initial setup.

Setup

We will need to download the application dependencies. You will need to have version 8.9.x of Node.js installed.

• Change to javascript directory: cd javascript
• Run the following command to install the required packages: npm install

Now we can start the network:

• Navigate back to the main FabToken directory: cd ..
• Start fabric network: ./startFabric.sh

This command will create a fabric network with 1 peer, an ordering service, one channel, and two users that our application will use to issue and transfer tokens.

Run the app right away

The fabtoken.js application includes a demo method that runs an end to end token flow with hardcoded parameters.

• Navigate to the javascript directory
• Run the command node fabtoken without any arguments to run the demo.

You should see the output of the demo in your terminal. The demo used user1 and user2 of the basic network to do the following token operations:

• Issue a token worth 100 USD as user1
• Transfer 30 USD from user1 to user2
• Redeem 10 USD as user1 and 30 USD as user2
• Check that user1 has a token worth 60 USD and user2 has no token

Use the sample app to create your own tokens

You can pass arguments to fabtoken.js to create your own tokens and follow your own token flow.

Issue tokens

Tokens need to be issued before they can be spent. You can use the command node fabtoken issue <username> <token_type> <quantity> to issue tokens of any type and quantity as user1 or user2.

• As an example, the first command issues a token worth 100 US dollars as user1. The second command issues a token worth 100 Euro's as user2:

node fabtoken issue user1 USD 100
node fabtoken issue user1 EURO 200

List tokens

After you issue tokens, you can use the list method to query the tokens that you own. Run the command node fabtoken list <username> You need to use this command to recover the tokenIDs that you will need to transfer or redeem your tokens.

• As an example, you can use the command below to list the tokens owned by user1:

node fabtoken list user1

• The command returns a list of tokens, with the tokenID consisting of a tx_id and index. You will need to use these values for future commands.

[ { id:
    { tx_id: 'ab5670d3b20b6247b17a342dd2c5c4416f79db95c168beccb7d32b3dd382e5a5',
      index: 0 },
    type: 'EURO',
    quantity: '200' },
  { id:
    { tx_id: 'c9b1211d9ad809e6ee1b542de6886d8d1d9e1c938d88eff23a3ddb4e8c080e4d',
      index: 0 },
    type: 'USD',
    quantity: '100' }
]

Transfer tokens

Tokens can be transferred between users on a channel using the node fabtoken transfer <from_user> <to_user> <quantity> <tx\_id> <index> command.

• <tx\_id> and <index> are the "tx_id" and "index" that you found using the list command
• <quantity> is the quantity to be transferred

Any remaing quantity will be transferred back to the owner by creating a new token with a new tokenID.

• As an example, the following commands transfers 30 dollars from user1 transfer to user2:

 node fabtoken transfer user1 user2 30 c9b1211d9ad809e6ee1b542de6886d8d1d9e1c938d88eff23a3ddb4e8c080e4d 0

You can run the command node fabtoken list user2 to verify that user2 now owns a token worth 30 dollars. You can also run the command node fabtoken list user1 to verify that a new token worth 70 dollars now belongs to user1.

Redeem tokens

Tokens can be taken out of circulation by being redeemed. Redeemed tokens can no longer be transfered to any member of the channel. Run the command node fabtoken redeem <username> <quantity> <tx\_id> <index> to redeem any tokens belonging to user1 or user2.

• <tx\_id> and <index> are the "tx_id" and "index" returned from the list command
• <quantity> is the quantity to be redeemed

Any remaing quantity will be transferred back to the owner with a new tokenID.

• As an example, the following command redeems 10 Euro's belonging to user1:

 node fabtoken redeem user2 10 ab5670d3b20b6247b17a342dd2c5c4416f79db95c168beccb7d32b3dd382e5a5 0

Clean up

If you are finished using the sample application, you can bring down the network and any accompanying artifacts.

• Change to fabric-samples/basic-network directory
• To stop the network, run ./stop.sh
• To completely remove all incriminating evidence of the network, run ./teardown.sh

Understanding the fabtoken.js application

You can examine the fabtoken.js file to get a better understanding of how the sample application uses the FabToken API's.

1. The createFabricClient method creates an instance of the fabric-client, and is used to connect to the components of your network.

2. The createUsers method uses the certificates generated by the basic network to create admin, user1 and user2 users for the application.

3. To perform token operations, you must create a TokenClient instance from a Client object. Make sure the client has set the user context. Below is the code snippet.

	// set user context to the client
	await client.setUserContext(user, true);

	// create a TokenClient instance
	const tokenClient = client.newTokenClient(channel, 'localhost:7051');

4. The issue method creates an issue request and submits the request to issue tokens to your network.

5. The list method submits the request to list tokens from a given owner, and is used to recover the tokenID if a token is being transfered or redeemed.

6. The transfer method creates a transfer request and submits the request to transfer tokens between users.

7. The redeem method creates a redeem request and submits the request to redeem a user's tokens.