> 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/the-open-network-ton/trylocatesourcetx-ton.md).

# trylocatesourcetx - TON

Example code for the trylocatesourcetx JSON-RPC method. Сomplete guide on how to use trylocatesourcetx JSON-RPC in GetBlock.io Web3 documentation.

This method attempts to locate the source transaction by the destination transaction parameters. Use it to trace back from an outcome to the originating message.

## Parameters

| Parameter   | Type   | Required | Description                          |
| ----------- | ------ | -------- | ------------------------------------ |
| source      | string | Yes      | Source address                       |
| destination | string | Yes      | Destination address                  |
| created\_lt | string | Yes      | Creation logical time of the message |

## Request Example

{% tabs %}
{% tab title="cURL" %}
**REST (GET):**

```bash
curl --location --request GET 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/tryLocateSourceTx?source=EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2&destination=EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2&created_lt=47652103000000' \
--header 'Content-Type: application/json'
```

**JSON-RPC (POST):**

```bash
curl --location --request POST 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "tryLocateSourceTx",
    "params": {
        "source": "EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2",
        "destination": "EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2",
        "created_lt": "47652103000000"
    },
    "id": "getblock.io"
}'
```

{% endtab %}

{% tab title="JavaScript (Axios)" %}

```javascript
import axios from 'axios';

const data = JSON.stringify({
    "jsonrpc": "2.0",
    "method": "tryLocateSourceTx",
    "params": {
        "source": "EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2",
        "destination": "EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2",
        "created_lt": "47652103000000"
    },
    "id": "getblock.io"
});

const config = {
    method: 'post',
    url: 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>',
    headers: {
        'Content-Type': 'application/json'
    },
    data: data
};

axios(config)
    .then(response => console.log(JSON.stringify(response.data, null, 2)))
    .catch(error => console.log(error));
```

{% endtab %}

{% tab title="Python (Requests)" %}

```python
import requests
import json

url = "https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/"

payload = json.dumps({
    "jsonrpc": "2.0",
    "method": "tryLocateSourceTx",
    "params": {
        "source": "EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2",
        "destination": "EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2",
        "created_lt": "47652103000000"
    },
    "id": "getblock.io"
})

headers = {
    'Content-Type': 'application/json'
}

response = requests.post(url, headers=headers, data=payload)
print(response.text)
```

{% endtab %}

{% tab title="Rust (Reqwest)" %}

```rust
use reqwest::Client;
use serde_json::json;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new();

    let payload = json!({
        "jsonrpc": "2.0",
        "method": "tryLocateSourceTx",
        "params": {
                "source": "EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2",
                "destination": "EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2",
                "created_lt": "47652103000000"
        },
        "id": "getblock.io"
});

    let response = client
        .post("https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>")
        .header("Content-Type", "application/json")
        .json(&payload)
        .send()
        .await?;

    let result: serde_json::Value = response.json().await?;
    println!("{:#?}", result);

    Ok(())
}
```

{% endtab %}
{% endtabs %}

## Response Example

{% code overflow="wrap" %}

```json
{
    "ok": true,
    "result": {
        "@type": "raw.transaction",
        "utime": 1737869730,
        "transaction_id": {
            "lt": "47652102999999",
            "hash": "ZyXwVu\u2026"
        }
    },
    "id": "getblock.io",
    "jsonrpc": "2.0"
}
```

{% endcode %}

## Response Parameters

| Field                       | Type   | Description                            |
| --------------------------- | ------ | -------------------------------------- |
| result.transaction\_id.lt   | string | Logical time of the source transaction |
| result.transaction\_id.hash | string | Hash of the source transaction         |

## Use Cases

* Tracing a destination event back to its originating transaction
* Reconstructing transaction graphs in indexers
* Forensics on suspicious activity

## Error Handling

| Status Code | Error Message       | Cause                                       |
| ----------- | ------------------- | ------------------------------------------- |
| 403         | Forbidden           | Missing or invalid `<ACCESS-TOKEN>`         |
| 422         | Validation Error    | Request parameters are missing or malformed |
| 429         | Too Many Requests   | Rate limit exceeded for your plan           |
| 504         | Lite Server Timeout | Upstream TON liteserver timed out           |

## SDK Integration

{% tabs %}
{% tab title="@ton/ton (JavaScript)" %}

```javascript
import { TonClient } from '@ton/ton';

const client = new TonClient({
    endpoint: 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/'
});

// The @ton/ton client wraps the same JSON-RPC methods.
// For low-level access, use client.callGetMethod or client.provider.
```

{% endtab %}

{% tab title="pytoniq (Python)" %}

```python
from pytoniq import LiteClient
# For HTTP API access, use ton-http-client or call the JSON-RPC
# endpoint directly with requests as shown in the Request Example.
```

{% endtab %}
{% endtabs %}