Is it possible to track marketplace sales for an ERC721?

Question

I know I can track events for smart contracts, such as Transfer and Approval for ERC20 and ERC721 or even ApprovalForAll for ERC721.

I also know that I can track my own defined events for any smart contract I deploy.

But is there a way to track an NFT sale in, let's say, OpenSea?

I was hoping that if I know the address of the OpenSea escrow smart contract (or any other marketplace), it is possible for me to know:

1. When a user transfers his/her token to it (using the Transfer event - which would mean "publishing a sale")

2. Immediately after, that an effective sale occurred, if there's another Transfer event from that escrow marketplace to an address different to the original

Does this make sense or am I just not seeing something?

Answer 1

Here is an example code on how you can track NFT transfer events on a smart contract using Moralis streams API.

import Moralis from "moralis";

const addStream = async () => {
  if (!Moralis.Core.isStarted) {
    await Moralis.start({
      apiKey: process.env.API_KEY,
    });
  }

  const options = {
    webhookUrl: "...", // Stream data will be sent to this webhook url
    description: "NFTTransfers",
    tag: "transfers",
    topic0: ["Transfer(address,address,uint256)"], // topic0 of your tracking
    allAddresses: false,
    includeNativeTxs: false,
    includeContractLogs: true,
    includeInternalTxs: false,
    getNativeBalances: [],
    triggers: [],
    abi: [
      {
        // ... Paste ABI as value
      },
    ],
    advancedOptions: null,
    chainIds: ["0x1", "0x5"], // chains on which you want to track events
  };

  const stream = await Moralis.Streams.add(options);

  // Attach the contract address to the stream
  await Moralis.Streams.addAddress({
    id: stream.raw.id,
    address: "0x..", //contract address on which you want to listen to streams to
  });
};
addStream();

The data received from the streams will have logs from the NFT transactions using which you can verify the marketplace address.

p.s. I work at Moralis