tendermint/docs/tendermint-core/subscription.md

---
order: 7
---

# Subscribing to events via Websocket

Tendermint emits different events, which you can subscribe to via
[Websocket](https://en.wikipedia.org/wiki/WebSocket). This can be useful
for third-party applications (for analysis) or for inspecting state.

[List of events](https://godoc.org/github.com/tendermint/tendermint/types#pkg-constants)

To connect to a node via websocket from the CLI, you can use a tool such as
[wscat](https://github.com/websockets/wscat) and run:

```sh
wscat ws://127.0.0.1:26657/websocket
```

You can subscribe to any of the events above by calling the `subscribe` RPC
method via Websocket along with a valid query.

```json
{
  "jsonrpc": "2.0",
  "method": "subscribe",
  "id": 0,
  "params": {
    "query": "tm.event='NewBlock'"
  }
}
```

Check out [API docs](https://docs.tendermint.com/master/rpc/) for
more information on query syntax and other options.

You can also use tags, given you had included them into DeliverTx
response, to query transaction results. See [Indexing
transactions](../app-dev/indexing-transactions.md) for details.

## ValidatorSetUpdates

When validator set changes, ValidatorSetUpdates event is published. The
event carries a list of pubkey/power pairs. The list is the same
Tendermint receives from ABCI application (see [EndBlock
section](https://github.com/tendermint/spec/blob/master/spec/abci/abci.md#endblock) in
the ABCI spec).

Response:

```json
{
  "jsonrpc": "2.0",
  "id": 0,
  "result": {
    "query": "tm.event='ValidatorSetUpdates'",
    "data": {
      "type": "tendermint/event/ValidatorSetUpdates",
      "value": {
        "validator_updates": [
          {
            "address": "09EAD022FD25DE3A02E64B0FE9610B1417183EE4",
            "pub_key": {
              "type": "tendermint/PubKeyEd25519",
              "value": "ww0z4WaZ0Xg+YI10w43wTWbBmM3dpVza4mmSQYsd0ck="
            },
            "voting_power": "10",
            "proposer_priority": "0"
          }
        ]
      }
    }
  }
}
```