> For the complete documentation index, see [llms.txt](https://docs.getblock.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.getblock.io/bsc-advanced-tooling/bsc-accelerated-dedicated-node/how-to-subscribe-to-stream.md). # How to Subscribe to Stream Stream subscription provides you with direct access to blockchain data as it propagates through the BDN network. This is very good for users e.g traders who want to get data earlier e.g new released token \ \ With a stream subscription, you enjoy: * **Faster blocks**: Receive new blocks before standard RPC propagation * **Mempool access**: See pending transactions before they're mined * **Lower latency:** Edge infrastructure minimizes network hops ### Code Sample Here, you will be checking if you are connected to streams {% tabs %} {% tab title="Endpoint" %} ```bash wss://go.getblock.io/ ``` {% endtab %} {% tab title="Code" %} {% code title="index.js" %} ```javascript //npm install ws dotenv import WebSocket from "ws"; import "dotenv/config"; const ws = new WebSocket( `wss://go.getblock.io/${process.env.ACCESS_TOKEN}`, ); ws.on("open", () => { console.log("Connected to BSC streams"); }); ws.on("error", (err) => { console.error("WebSocket error:", err.message); }); ``` {% endcode %} {% endtab %} {% tab title="Response" %} ```bash > bsc-node@1.0.0 start > node index.js Connected to BSC streams ``` {% endtab %} {% endtabs %} ### How to Subscribe to Streams To subscribe to streams, there are four parameters you can make use of as seen below: | Stream | Description | Use Case | | ------------ | ---------------------------------------- | --------------------------- | | `bdnBlocks` | New blocks with headers and transactions | Block monitoring, analytics | | `newTxs` | New transactions entering mempool | MEV detection, copy trading | | `pendingTxs` | Pending transactions | Front-running protection | | `txReceipts` | Transaction receipts after confirmation | Trade confirmation | #### 1. Block Streams (bdnBlocks) Subscribe to new blocks as they're produced. **Include Options** | Field | Description | | -------------- | --------------------------------------------------------- | | `header` | Block header (number, hash, timestamp, gasUsed, gasLimit) | | `transactions` | Full transaction list | | `hash` | Block hash only | **Example: Subscribe to Blocks** {% tabs %} {% tab title="Code" %} {% code title="subscribe-blocks.js" %} ```javascript import WebSocket from "ws"; import "dotenv/config"; const ws = new WebSocket(`wss://go.getblock.io/${process.env.ACCESS_TOKEN}`); ws.on("open", () => { console.log("Connected"); // Subscribe to new blocks ws.send( JSON.stringify({ jsonrpc: "2.0", id: 1, method: "subscribe", params: ["bdnBlocks", { include: ["header", "transactions", "hash"] }], }), ); }); ws.on("message", (data) => { const message = JSON.parse(data); // Subscription confirmation if (message.id === 1 && message.result) { console.log("Subscribed! ID:", parseInt(message.result)); return; } // Block notification if (message.params?.result) { const block = message.params.result; console.log("New block:", { number: parseInt(block.header.number, 16), hash: block.header.hash, txCount: block.transactions?.length || 0, }); } }); ``` {% endcode %} {% endtab %} {% tab title="Response" %} ```json Connected Subscribed! ID: 9 New block: { number: 84411561, hash: undefined, txCount: 86 } New block: { number: 84411562, hash: undefined, txCount: 105 } New block: { number: 84411563, hash: undefined, txCount: 66 } New block: { number: 84411564, hash: undefined, txCount: 66 } New block: { number: 84411565, hash: undefined, txCount: 78 } New block: { number: 84411566, hash: undefined, txCount: 93 } New block: { number: 84411567, hash: undefined, txCount: 63 } ``` {% endtab %} {% endtabs %} #### 2. Transaction Streams (newTxs / pendingTxs) Subscribe to mempool transactions as they propagate through the network. **Include Options** | Field | Description | | ----------- | ----------------------- | | `tx_hash` | Transaction hash | | `from` | Sender address | | `to` | Recipient address | | `value` | Transaction value (hex) | | `gas_price` | Gas price (hex) | | `input` | Transaction calldata | **Filters** Reduce bandwidth by filtering server-side: | Filter | Type | Description | | ----------- | ----- | ---------------------------------------------- | | `to` | array | Transaction recipient addresses | | `from` | array | Transaction sender addresses | | `method_id` | array | Function selectors (first 4 bytes of calldata) | **Example: Monitor PancakeSwap Transactions** {% tabs %} {% tab title="pendingTxs code" %} 
import WebSocket from "ws";
import { ethers } from "ethers";
import "dotenv/config";

const PANCAKE_ROUTER = "0x10ED43C718714eb63d5aA57B78B54704E256024E";

const SWAP_METHODS = {
  "0x38ed1739": "swapExactTokensForTokens",
  "0x7ff36ab5": "swapExactETHForTokens",
  "0x18cbafe5": "swapExactTokensForETH",
  "0xfb3bdb41": "swapETHForExactTokens",
  "0x5c11d795": "swapExactTokensForTokensSupportingFeeOnTransferTokens",
  "0xb6f9de95": "swapExactETHForTokensSupportingFeeOnTransferTokens",
};

function monitorPancakeSwap() {
  const ws = new WebSocket(`wss://go.getblock.io/${process.env.ACCESS_TOKEN}`);

  ws.on("open", () => {
    console.log("🔌 Connected to BSC stream");
    console.log("đź“Š Monitoring PancakeSwap...\n");

    ws.send(
      JSON.stringify({
        jsonrpc: "2.0",
        id: 1,
        method: "subscribe",
        params: [
          "pendingTxs",
          {
            include: ["tx_hash", "from", "to", "value", "input", "gas_price"],
            filters: {
              to: [PANCAKE_ROUTER],
            },
          },
        ],
      }),
    );
  });

  ws.on("message", (data) => {
    const msg = JSON.parse(data);

    // Subscription confirmed
    if (msg.id === 1) {
      console.log("âś… Subscribed to PancakeSwap transactions\n");
      return;
    }

    // New transaction
    if (msg.params?.result) {
      const tx = msg.params.result;
      const methodId = tx.input?.slice(0, 10);
      const methodName = SWAP_METHODS[methodId] || "unknown";

      if (SWAP_METHODS[methodId]) {
        const value = ethers.formatEther(tx.value || "0");
        const gasPrice = ethers.formatUnits(tx.gas_price || "0", "gwei");

        console.log("🔄 Swap detected:");
        console.log(`   Hash: ${tx.tx_hash.slice(0, 18)}...`);
        console.log(`   Method: ${methodName}`);
        console.log(`   From: ${tx.from.slice(0, 10)}...`);
        console.log(`   Value: ${value} BNB`);
        console.log(`   Gas: ${gasPrice} gwei`);
        console.log("");
      }
    }
  });

  ws.on("close", () => {
    console.log("Disconnected, reconnecting in 5s...");
    setTimeout(monitorPancakeSwap, 5000);
  });

  ws.on("error", (err) => {
    console.error("WebSocket error:", err.message);
  });
}

monitorPancakeSwap();
{% endtab %} {% tab title="Response" %} ```json { "tx_hash": "0xdef456...", "from": "0xabc...", "to": "0x10ED43C718714eb63d5aA57B78B54704E256024E", "value": "0x16345785d8a0000", "gas_price": "0xb2d05e00", "input": "0x38ed1739..." } ``` {% endtab %} {% tab title="newTx code" %} 
import WebSocket from 'ws';
import 'dotenv/config';

const PANCAKE_ROUTER = '0x10ED43C718714eb63d5aA57B78B54704E256024E';

const SWAP_METHODS = {
  '0x38ed1739': 'swapExactTokensForTokens',
  '0x7ff36ab5': 'swapExactETHForTokens',
  '0x18cbafe5': 'swapExactTokensForETH',
  '0xfb3bdb41': 'swapETHForExactTokens',
};

function monitorNewTxs() {
  const ws = new WebSocket(`wss://go.getblock.io/${process.env.ACCESS_TOKEN}`);

  ws.on('open', () => {
    console.log('Connected to BSC stream');
    console.log('Monitoring confirmed PancakeSwap swaps...\n');

    ws.send(JSON.stringify({
      jsonrpc: '2.0',
      id: 1,
      method: 'subscribe',
      params: ['newTxs', {
        include: ['tx_hash', 'from', 'to', 'value', 'input'],
        filters: {
          to: [PANCAKE_ROUTER],
          method_id: Object.keys(SWAP_METHODS)
        }
      }]
    }));
  });

  ws.on('message', (data) => {
    const msg = JSON.parse(data);

    if (msg.id === 1) {
      console.log('Subscribed to confirmed PancakeSwap transactions\n');
      return;
    }

    if (msg.params?.result) {
      const tx = msg.params.result;
      const methodId = tx.input?.slice(0, 10);
      const methodName = SWAP_METHODS[methodId] || 'unknown';

      console.log('Confirmed swap:');
      console.log(`  Hash:   ${tx.tx_hash}`);
      console.log(`  Method: ${methodName}`);
      console.log(`  From:   ${tx.from}`);
      console.log(`  To:     ${tx.to}`);
      console.log(`  Value:  ${tx.value}`);
      console.log('');
    }
  });

  ws.on('close', () => {
    console.log('Disconnected, reconnecting in 5s...');
    setTimeout(monitorNewTxs, 5000);
  });

  ws.on('error', (err) => {
    console.error('WebSocket error:', err.message);
  });
}

monitorNewTxs();
{% endtab %} {% tab title="Response" %} {% code overflow="wrap" %} ```bash { "jsonrpc":"2.0", "id":1, "result":"0x11" } ``` {% endcode %} {% endtab %} {% endtabs %} #### 3. Transaction Receipts (txReceipts) Subscribe to transaction confirmations. **Include Options** | Field | Description | | --------- | ------------------------ | | `receipt` | Full transaction receipt | | `logs` | Event logs emitted | Example: {% tabs %} {% tab title="Code" %} 
import WebSocket from 'ws';
import 'dotenv/config';

const ws = new WebSocket(`wss://go.getblock.io/${process.env.ACCESS_TOKEN}`);

ws.on("open", () => {
  console.log("Connected");

  // Subscribe to new blocks
  ws.send(JSON.stringify({
    jsonrpc: '2.0',
    id: 1,
    method: 'subscribe',
    params: ['txReceipts', {
      include: ['receipt', 'logs']
    }]
  }));
});

ws.on("message", (data) => {
  const message = JSON.parse(data);
  console.log(message)})
{% endtab %} {% tab title="Response" %} {% code overflow="wrap" %} ```bash { jsonrpc: '2.0', id: 1, result: '0x10' } ``` {% endcode %} {% endtab %} {% endtabs %} #### Unsubscribing To stop receiving notifications, unsubscribe using the subscription ID: {% tabs %} {% tab title="code sample" %} {% code title="unsubscribe.js" overflow="wrap" %} ```js import WebSocket from "ws"; import "dotenv/config"; const ws = new WebSocket(`wss://go.getblock.io/${process.env.ACCESS_TOKEN}`); ws.on("open", () => { console.log("Connected"); ws.send( JSON.stringify({ jsonrpc: "2.0", id: 10, method: "unsubscribe", params: ["23"], // Subscription ID }), );}) ws.on("message", (data) => { const message = JSON.parse(data); console.log(JSON.stringify(message, null, 2)); }); ``` {% endcode %} {% endtab %} {% tab title="Response" %} {% code overflow="wrap" %} ```bash { jsonrpc: '2.0', id: 10, result: true } ``` {% endcode %} {% endtab %} {% endtabs %} ## Best Practices 1\. Request Only What You Need {% tabs %} {% tab title="Don't ❌" %} ```js // ❌ Bad: Request everything include: ['tx_contents'] // Large payloads, high bandwidth ``` {% endtab %} {% tab title="Do ✅" %} ```js // ✅ Good: Request specific fields include: ['tx_hash', 'from', 'to', 'value'] // Small payloads ``` {% endtab %} {% endtabs %} 2. Use Server-Side Filters {% tabs %} {% tab title="Don't ❌" %} ```js // ❌ Bad: Filter client-side params: ['newTxs', { include: ['tx_contents'] }] // Then filter in your code... wasteful! ``` {% endtab %} {% tab title="Do ✅" %} ```js // ✅ Good: Filter server-side params: ['newTxs', { include: ['tx_hash', 'to', 'input'], filters: { to: ['0xTargetContract'] } }] ``` {% endtab %} {% endtabs %} 3. Handle Reconnection ```javascript function createConnection() { const ws = new WebSocket(`wss://bsc.getblock.io/mev/ws?api_key=${API_KEY}`); ws.on('close', () => { console.log('Disconnected, reconnecting...'); setTimeout(createConnection, 5000); }); ws.on('open', () => { // Re-subscribe after reconnect subscribeToFeeds(ws); }); return ws; } ``` 4. Process Messages Asynchronously ```javascript ws.on('message', async (data) => { // Don't block the message loop setImmediate(() => { processMessage(JSON.parse(data)); }); }); ``` ## Rate Limits | Tier | Concurrent Subscriptions | Message Rate | | ---------- | ------------------------ | ------------ | | Standard | 5 | 1,000/sec | | Pro | 20 | 10,000/sec | | Enterprise | Unlimited | Unlimited | ***Contact*** [***support***](mailto:support@getblock.io) ***to upgrade your tier.*** ## Troubleshooting | Problem | Solution | | -------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | No messages received |

| | High latency |

| | Missed messages |

| | Connection Drop |

| ### Next Step 1. [Submitting transactions to public mempool ](/bsc-advanced-tooling/bsc-accelerated-dedicated-node/how-to-submit-transactions-to-public-mempool.md)with accelerated propagation 2. Using private transactions for [MEV protection ](/bsc-advanced-tooling/bsc-accelerated-dedicated-node/sending-transactions-to-private-mempool-priority-fee.md)or [without MEV Protection](/bsc-advanced-tooling/bsc-accelerated-dedicated-node/how-to-submit-transaction-to-private-mempool.md) --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.getblock.io/bsc-advanced-tooling/bsc-accelerated-dedicated-node/how-to-subscribe-to-stream.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.