Ethereum: How to use WalletNotify

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WalletNotify is a mechanism to receive notifications from your Ethereum wallet when specific events occur, such as balance updates, transaction approvals, or even the creation of new Ethereum nodes. It is an optional feature that allows you to stay informed about your wallet’s activities in real-time.

Using WalletNotify with JSON-RPC

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To use WalletNotify with a JSON-RPC call, you need to create a file called walletnotify.json in the root directory of your Ethereum node configuration. This file specifies the notification handlers that your wallet should follow.

Here is an example of what this file might look like:

{
"notify": {
"transactions": [
{
"event": "transaction.created",
"handler": "handle_transaction_created"
},
{
"event": "balance.increase",
"handler": "handle_balance_increase"
}
]
},
"handler": {
"type": "json-rpc",
"method": "eth_getTransactionCount",
"params": [],
"callOptions": {},
"value": {}
}
}

In this example, we are specifying two notification handlers: handle_transaction_created and handle_balance_increase. The transaction.created event is triggered when a new Ethereum transaction is created, while the balance.increase event is triggered when the wallet balance increases.

How to write in walletnotify.json

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To use WalletNotify with your wallet daemon, you need to write a script (called transaction.sh) that generates an HTTP request for each notification. This script should call the JSON-RPC method specified in the walletnotify.json file.

Here is an example of what this script might look like:

#!/bin/bash









Get the current transaction count
TX_COUNT=$(eth_getTransactionCount)

Create a notification message
printf "Transaction created: %s\n" $(echo "$TX_COUNT")

Call the JSON-RPC method to get the new transaction count
eth_getTransactionCount --gaslimit=2000000 --value=0 100

This script generates an HTTP request with the following headers:

• Content-Type: application/json

• X-ChainId: the Ethereum chain ID (usually 0)

• X-Priority: the priority level of the notification (usually 5)

The response from the wallet daemon should be a JSON object containing the updated transaction count. You can then parse this response and use it as needed.

Use case example

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Let’s say you want to receive notifications when your Ethereum balance increases or when new transactions are created on the testnet. You would create a walletnotify.json file with the following content:

{
"notify": {
"transactions": [
{
"event": "balance.increase",
"handler": "handle_balance_increase"
},
{
"event": "transaction.created",
"handler": "handle_transaction_created"
}
]
},
"handler": {
"type": "json-rpc",
"method": "eth_getTransactionCount",
"params": [],
"callOptions": {},
"value": {}
}
}

Then, you would run the transaction.sh script to generate HTTP requests for each notification. You can use a tool like curl or a web browser’s developer tools to inspect these requests and see how they are being used.

Conclusion

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WalletNotify is an optional feature that allows you to stay informed about your Ethereum wallet activities in real-time. By specifying notification handlers in `walletnotify.