eth_subscribe

Use this API to create a subscription for specific events (newHeads, logs, newPendingTransactions).

Usage Notes

You must use a wss endpoint when connecting; https is not supported.
If the WebSocket connection is lost, subscriptions may be automatically cancelled. If the connection drops, you must re-subscribe.
CU is consumed based on the amount of data subscribed, so it is recommended to use appropriate filtering options to subscribe only to the data you need.

1.Request Parameters

All subscription requests share the following common parameters.

Parameter	Type	Required	Description
id	integer or string	required	A unique identifier for each request. Used by the client to match requests with server responses. Typically expressed as a number or string.
jsonrpc	string	required	Indicates the version of the JSON-RPC protocol. The version used in this network is "2.0", so always use this value.
method	string	required	Specifies the name of the specific JSON-RPC method to execute. Enter "eth_subscribe" here.
params	array	required	Passes the arguments required for execution as an array. In "eth_subscribe", enter one of the subscription types: newHeads, logs, or newPendingTransactions, along with any required information for that subscription type.

The arguments passed in params differ depending on the subscription type. The following describes the arguments for each subscription type.

Subscription Type

`newHeads`

Subscribing to this event sends the header information of each new block in real time whenever a new block is created. The table below shows detailed information about the arguments that must be entered inside the params array.

Argument	Type	Required	Description
subscription_type	string	required	Specifies the event type to subscribe to. Enter "newHeads" here.

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_subscribe",
  "params": ["newHeads"]
}

`logs`

Subscribing to this event sends information in real time whenever a specific log occurs. Users can use the address and topics fields to filter events related to a specific smart contract address. For example, you can subscribe to logs for events such as ERC-20 or ERC-721 token transfers. If you enter an empty filtering option, all logs will be returned, so it is recommended to always specify the necessary filtering options. The table below shows detailed information about the arguments that must be entered inside the params array.

Argument	Type	Required	Description
subscription_type	string	required	Specifies the event type to subscribe to. Enter "logs" here.
filtering_option	object	required	Specifies options (address, topics) for filtering logs. If an empty object is passed, all logs that occur will be returned. It is recommended to specify the desired filtering options based on your use case.
filtering_option.address	string	optional	Filters by a specific address.
filtering_option.topics	array	optional	Enter the topics to filter as an array.

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_subscribe",
  "params": [
    "logs",
    {
      "address": "0xdAC17F958D2ee523a2206206994597C13D831ec7",
      "topics": [
        "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"
      ]
    }
  ]
}

`newPendingTransactions`

Subscribing to this event sends the information of a transaction in real time when it is submitted to the network. The table below shows detailed information about the arguments that must be entered inside the params array.

Argument	Type	Required	Description
subscription_type	string	required	Specifies the event type to subscribe to. Enter "newPendingTransactions" here.
flag	boolean	optional	Specifies whether to include full transaction data. If true, returns the full transaction data; if false, returns only the transaction hash. If not specified, defaults to false and returns only the transaction hash.

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_subscribe",
  "params": ["newPendingTransactions", true]
}

2. Response

Once a subscription is created using the parameters above, you will receive the following responses whenever an event occurs.

{
  "jsonrpc": "2.0",
  "method": "eth_subscription",
  "params": {
    "subscription": "0x71bf7fd5f1d909400aefbd04c96474e8",
    "result": {
      "parentHash": "0xef887cc02d9dcc195319201e78a5bf136ed68df16e30c6fe08e21a7d123b3612",
      "sha3Uncles": "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",
      "miner": "0x95222290dd7278aa3ddd389cc1e1d165cc4bafe5",
      "stateRoot": "0x401c9af726edb8cc0c96ccfe6fc8cd016fc2e1e4e1ebf90f52a9560d416e78b9",
      "transactionsRoot": "0x11747f43d21022eec362e8ca7b055b4e4417abb6ed12fbd2baae7817b407e614",
      "receiptsRoot": "0xa467e9c0ac6530a0f33c60bd0e799295811da732708cc338a00dcee9ab8794f0",
      "logsBloom": "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",
      "difficulty": "0x0",
      "number": "0x13c5e89",
      "gasLimit": "0x1c9c380",
      "gasUsed": "0x8b58db",
      "timestamp": "0x66e2b143",
      "extraData": "0x6265617665726275696c642e6f7267",
      "mixHash": "0xd03523217638366b0bd1111d29108f0fc3789ab21e6a9e7afe4ab568f3b98a64",
      "nonce": "0x0000000000000000",
      "baseFeePerGas": "0x828e8440",
      "withdrawalsRoot": "0x5584306249ecc33fa9c0b1804b461ec16abcb305d646fcba128bca75e1700f4a",
      "blobGasUsed": "0x0",
      "excessBlobGas": "0xe0000",
      "parentBeaconBlockRoot": "0x9814d97d13152344553575788f0c6853c7d23f8c521201793257bb7c0c14fe59",
      "hash": "0x9f30ee57944013169c179c9c954aaf60a8bf785b166cc49f58dcc5ce28ecae96"
    }
  }
}

{
  "jsonrpc": "2.0",
  "method": "eth_subscription",
  "params": {
    "subscription": "0x3b7f71db357fe4e9edd8f2e6ec6b24a6",
    "result": {
      "address": "0xdac17f958d2ee523a2206206994597c13d831ec7",
      "topics": [
        "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef",
        "0x0000000000000000000000003ef97e73d4b8e06535e24aab125077d16462318b",
        "0x0000000000000000000000004af688bb824d12cff5c339abf3010ce7806afcd0"
      ],
      "data": "0x00000000000000000000000000000000000000000000000000000002540be400",
      "blockNumber": "0x13c5e92",
      "transactionHash": "0x283b803e4ed34b03674d04ed71b48d6879034ebfa564acccb8b7b48715d25e0d",
      "transactionIndex": "0x1",
      "blockHash": "0x492384316ea319b4f929306492746155d011f08a3b173e6e4eee9e82faeef207",
      "logIndex": "0x0",
      "removed": false
    }
  }
}

{
  "jsonrpc": "2.0",
  "method": "eth_subscription",
  "params": {
    "subscription": "0x7f708f4295996c21dbf16e6fcdd8c9e3",
    "result": {
      "blockHash": null,
      "blockNumber": null,
      "from": "0x194981ee45d9ead1f67e7b2299153f0cf06ed542",
      "gas": "0x1061f",
      "gasPrice": "0xb2d05e00",
      "hash": "0x410d09342c540808a1a10eabebc6189b6786fad04c3ac88b7098243b0112d6e1",
      "input": "0xa9059cbb00000000000000000000000046e0e692e8cf2aecb75cdece4be2e110a82069b000000000000000000000000000000000000000000000000009f593793582b31c",
      "nonce": "0x8",
      "to": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2",
      "transactionIndex": null,
      "value": "0x0",
      "type": "0x0",
      "chainId": "0x1",
      "v": "0x25",
      "r": "0xa0fbb1a0613b7e07b49b1e6585f75a0d92df71ee8482551a5d9dfbd82011a1eb",
      "s": "0x1271bfa29a4306b02d8d4c09dc467c540d5837110d8f43b3fd52bfed09351b59"
    }
  }
}

3. How to use

This API is a WebSocket-based API that can be subscribed to using a tool for WebSocket communication. The WebSocket client tool used in this example is wscat, which makes it easy to connect to a WebSocket server and send/receive data.

3.1. Connect to Websocket channel

Open a terminal window and enter the command below. At this point, you must specify the protocol and network you want to subscribe to, and enter the API key of the project created in the console.

# Set protocol, network and your api key in the URL to connect (e.g., wss://ethereum-mainnet.nodit.io/FwG...)
wscat -c wss://{protocol}-{network}.nodit.io/{your_api_key}

Once the WebSocket connection is established, subscribe to the desired event from the examples below.

{ "jsonrpc": "2.0", "id": 1, "method": "eth_subscribe", "params": ["newHeads"] }

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_subscribe",
  "params": [
    "logs",
    {
      "address": "0xdAC17F958D2ee523a2206206994597C13D831ec7",
      "topics": [
        "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"
      ]
    }
  ]
}

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_subscribe",
  "params": ["newPendingTransactions", true]
}

3.3. Listen subscription

The very first response returns the subscription ID.

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0xb273410795d4411d707f272834cdd60e"
}

After that, each time an event occurs, results matching the subscription type are returned.

{
  "jsonrpc": "2.0",
  "method": "eth_subscription",
  "params": {
    "subscription": "0xb273410795d4411d707f272834cdd60e",
    "result": {
        # ...
    }
  }
}

3.4. Unsubscribe

Pressing Ctrl+C in the terminal window to close the connection will cancel the subscription. Alternatively, you can use eth_unsubscribe to cancel the subscription while keeping the connection alive. Send the subscription ID connected to the channel in the params as shown in the example below to cancel that subscription.

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_unsubscribe",
  "params": ["0x540e1706d67fd05fc8f3318dc7e86fc7"]
}

If the subscription was successfully cancelled, you will receive the following response.

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": true
}

1.Request Parameters​

Subscription Type​

newHeads​

logs​

newPendingTransactions​

2. Response​

3. How to use​

3.1. Connect to Websocket channel​

3.2. Subscribe a specific event​

3.3. Listen subscription​

3.4. Unsubscribe​