How to Subscribe to Pending Transactions via WebSocket Endpoints

This is to learn subscribing to pending transactions via WebSockets, and filters the transactions based on specified from and/or to addresses.
Tokenview provides the most direct WebSockets to subscribe to pending transactions, log events, and new blocks using WebSockets on Ethereum, BNB Smart Chain, Ethereum Classic and Kucoin Community Chain. You're able to implement this by simply connecting to each endpoint. In this article, we will mainly focus on pending transactions.

Endpoints

newPendingTransactions
tokenview_pendingTransactions

What significance does the tokenview_pendingTransactions provide to users?

tokenview_pendingTransactions is a filter for newPendingTransactions, what you received from the endpoint are filtered already, whereas the newPendingTransactions will return a bunch of, vast of unrelated transactions for your focus.

• Watching for pending transactions sent to a set of NFT owners to track the most recent floor price
• Watching transactions sent from a whale trader to track trading patterns

What is difference tokenview_pendingTransactions compare to newPendingTransactions?

Both enable developers to receive pending transaction that are sent to the network and marked as "pending". However, tokenview_pendingTransactions enhance the developer experience by providing filters that can specify based on to/from addresses.

• fromAddress (optional): string or [array of strings]
  • Singular address or array of addresses to receive pending transactions sent from this address.
• toAddress (optional): string or [array of strings]
  • Singular address or array of addresses to receive pending transactions to this address
• hashesOnly (optional): boolean default value is false. where the response matches the payload of eth_getTransactionByHash . If set to true, the payload returned contains only the hashes of the transactions that are added to the pending state, which matches the payload of newPendingTransactions

Subscribe newPendingTransactions

Here's a basic example using wscat to subscribe to new pending transactions:

1. Initiate the WebSocket stream
2. Enter the specific call command

// initiate websocket stream first
wscat -c wss://services.tokenview.io/vipapi/websocket/node/{network}/{apikey}

// then call subscription 
{ "id": 1, "jsonrpc": "2.0", "method": "eth_subscribe", "params": ["newPendingTransactions"] }

If successful, you should see output that looks something like this:

{ "id": 1, "jsonrpc": "2.0", "result": "0xc3b33aa549fb9a60e95d21862596617c" }
{
  "jsonrpc":"2.0",
  "method":"eth_subscription",
  "params":{
    "subscription":"0xc3b33aa549fb9a60e95d21862596617c",
    "result":"0xd6fdc5cc41a9959e922f30cb772a9aef46f4daea279307bc5f7024edc4ccd7fa"
  }
}

Once you get the result, it is actually a transaction hash, then you can use Tokenview Blockchain API to get the transaction details.

Filter Pending Transactions

We will demonstrate how to filter pending transactions using the tokenview_pendingTransactions subscription based on an address or array of addresses to receive pending transactions sent from this address (fromAddress) and to this address (toAddress).

1. Initiate the WebSocket stream
2. Enter the specific call command

// initiate websocket stream first
wscat -c wss://services.tokenview.io/vipapi/websocket/node/{network}/{apikey}

// then call subscription 
{ "id": 1, "jsonrpc": "2.0", "method": "eth_subscribe", "params": ["tokenview_pendingTransactions", {"toAddress": ["0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48", "0xdAC17F958D2ee523a2206206994597C13D831ec7"], "hashesOnly": false}] }

If successful, you should see output that looks something like this:

{
    "jsonrpc": "2.0",
    "method": "eth_subscription",
    "params": {
        "subscription": "0x2ab5239be033147ad679afe7e571e5a1",
        "result": {
            "blockHash": "null",
            "blockNumber": "null",
            "from": "0x2f4e7d5d324982ef77cd259b9385e77d122f12a5",
            "gas": "0xe407",
            "gasPrice": "0x1697cbdf4",
            "hash": "0x74759f6b716b700b740416a1f91082c7bb101f3aec7146fe3cdf6069a33804bb",
            "input": "0x23b872dd0000000000000000000000002e4da61e09709a6b78478e204fb657a2c5e890730000000000000000000000000fb8becf4fe62c0af8bc15c4022d4287419f4db0000000000000000000000000000000000000000000000000000000005a1510d0",
            "nonce": "0x49",
            "to": "0xdac17f958d2ee523a2206206994597c13d831ec7",
            "transactionIndex": "null",
            "value": "0x0",
            "type": "0x0",
            "chainId": "0x1",
            "v": "0x25",
            "r": "0xc2db03ad2fd312d934145b3ac86836bb050a4482db653aacc92ea62051c92517",
            "s": "0x43edc098e8fdcb7c0cb16762623c8cb2af9f92ca2865eb0fc01e0447893508d2"
        }
    }
}

About Tokenview Blockchain APIs & Data Service Platform:

Tokenview blockchain APIs & data service platform contained 120+ blockchains has powerful endpoints that simplify complex blockchain data into single API calls. Code for all supported blockchains using unified API calls. From here to easily get transaction, address, gas, contract, token, NFT, logs and any information from chain. And Yes you can also send tx to chain. One-click configuration with APIKey helps developers to Use, to Create, to Build.