> 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/api-reference/tron-trx/tron-grpc-api/triggerconstantcontract-tron.md).

# TriggerConstantContract - Tron

This method executes a read-only smart-contract call locally, without creating a transaction. It is the primary method for reading contract state, such as a TRC-20 balance, and returns the result in `constant_result`.

## Service

This method is served by the `protocol.Wallet` and `protocol.WalletSolidity` service.

{% hint style="info" %}
This is a read method. It is also served by `protocol.WalletSolidity`, which returns only confirmed, irreversible data. Use the Solidity service for balance and payment verification.
{% endhint %}

## Method

```protobuf
rpc TriggerConstantContract (TriggerSmartContract) returns (TransactionExtention)
```

## Request Message

`TriggerSmartContract`

| Field             | Type  | Description                                         |
| ----------------- | ----- | --------------------------------------------------- |
| owner\_address    | bytes | Caller address as raw bytes                         |
| contract\_address | bytes | Contract address as raw bytes                       |
| data              | bytes | ABI-encoded call data (selector + arguments)        |
| call\_value       | int64 | TRX in SUN to send with the call                    |
| fee\_limit        | int64 | Maximum TRX in SUN to spend on Energy (write calls) |

## Request

{% tabs %}
{% tab title="grpcurl" %}
{% code overflow="wrap" %}

```bash
grpcurl -H 'x-api-key: <ACCESS-TOKEN>' \
  -d '{"owner_address": "41f0cc5a2a84cd0f68ed1667070934542d673acbd8", "contract_address": "41a614f803b6fd780986a42c78ec9c7f77e6ded13c", "data": "70a08231000000000000000000000000f0cc5a2a84cd0f68ed1667070934542d673acbd8"}' \
  shared.eu-central-1.getblock.io:443 protocol.Wallet/TriggerConstantContract
```

{% endcode %}
{% endtab %}

{% tab title="Python" %}
{% code title="example.py" %}

```python
import grpc
# Stubs generated from java-tron's api.proto with grpcio-tools
from api import api_pb2_grpc
from core import Contract_pb2, Tron_pb2

creds = grpc.ssl_channel_credentials()
channel = grpc.secure_channel('shared.eu-central-1.getblock.io:443', creds)
metadata = [('x-api-key', '<ACCESS-TOKEN>')]
stub = api_pb2_grpc.WalletStub(channel)

response = stub.TriggerConstantContract(Contract_pb2.TriggerSmartContract(
    owner_address=bytes.fromhex('41f0cc5a2a84cd0f68ed1667070934542d673acbd8'),
    contract_address=bytes.fromhex('41a614f803b6fd780986a42c78ec9c7f77e6ded13c'),
    data=bytes.fromhex('70a08231...')), metadata=metadata)
print(response)
```

{% endcode %}
{% endtab %}

{% tab title="Go" %}
{% code title="example.go" %}

```go
conn, _ := grpc.Dial(
    "shared.eu-central-1.getblock.io:443",
    grpc.WithTransportCredentials(credentials.NewTLS(&tls.Config{})),
)
defer conn.Close()

client := api.NewWalletClient(conn)
ctx := metadata.AppendToOutgoingContext(
    context.Background(), "x-api-key", "<ACCESS-TOKEN>")

resp, _ := client.TriggerConstantContract(ctx, &core.TriggerSmartContract{OwnerAddress: owner, ContractAddress: contract, Data: callData})
fmt.Println(resp)
```

{% endcode %}
{% endtab %}
{% endtabs %}

## Response Message

`TransactionExtention`

| Field            | Type           | Description                                        |
| ---------------- | -------------- | -------------------------------------------------- |
| constant\_result | repeated bytes | ABI-encoded return data of the call                |
| energy\_used     | int64          | Energy the call would consume as a transaction     |
| result           | Return         | Execution result, with a result flag and any error |

## Use Cases

* **Token Balances**: Read a TRC-20 balance with balanceOf
* **Contract State**: Read view and pure functions without a transaction
* **Price Feeds**: Query on-chain oracle values
* **Energy Estimation**: Read energy\_used to size a later transaction

## Error Handling

| Code | Status            | Description                                                 |
| ---- | ----------------- | ----------------------------------------------------------- |
| 3    | INVALID\_ARGUMENT | A request field is missing or malformed                     |
| 5    | NOT\_FOUND        | The requested account, block, or transaction does not exist |
| 16   | UNAUTHENTICATED   | The access token is missing or invalid                      |
| 13   | INTERNAL          | The node failed to process the request                      |