nextTransaction - Cardano

Example code for the nextTransaction WebSocket method. Complete guide on how to use nextTransaction WebSocket in GetBlock Web3 documentation.

This method returns the next transaction in the acquired mempool snapshot, allowing a client to list all pending transactions one at a time. This protocol requires a WebSocket connection.

Parameters

Parameter	Type	Required	Description
fields	string	No	Set to "all" to return full transaction objects instead of ids

Request

JavaScript

example.js

import WebSocket from 'ws';

const client = new WebSocket('wss://go.getblock.io/<ACCESS-TOKEN>/');

client.once('open', () => {
    client.send(JSON.stringify({"jsonrpc": "2.0", "method": "nextTransaction", "params": {"fields": "all"}, "id": "getblock.io"}));
});

client.on('message', (msg) => {
    console.log(JSON.parse(msg.toString()));
    client.close();
});

Python

example.py

import asyncio
import json
import websockets

async def main():
    async with websockets.connect('wss://go.getblock.io/<ACCESS-TOKEN>/') as ws:
        await ws.send(json.dumps({"jsonrpc": "2.0", "method": "nextTransaction", "params": {"fields": "all"}, "id": "getblock.io"}))
        print(json.loads(await ws.recv()))

asyncio.run(main())

Response

{
    "jsonrpc": "2.0",
    "method": "nextTransaction",
    "result": {
        "transaction": {
            "id": "10b54fd708ab2e5703979b4ba27ca0339882abc2062e77fbe51e625203a49642"
        }
    },
    "id": "getblock.io"
}

Response Parameters

Field	Type	Description
transaction	object	The next mempool transaction, or null when the snapshot is exhausted

Use Cases

• Mempool Listing: Enumerate all pending transactions in a snapshot

• Payment Detection: Detect an incoming transaction before confirmation

• Fee Analysis: Collect pending transactions for fee modeling

• Monitoring: Feed pending transactions into an alerting pipeline

Error Handling

Error Code	Message	Description
-32602	Invalid params	The request is malformed for the current protocol state
4000	Must acquire mempool	A snapshot must be acquired before this request
-32603	Internal error	The node failed to answer the mempool request