# Cancel Order

## Cancel Order API

Cancel an existing open order by signing its hash.

### Overview

Order cancellation requires:

1. The hash of the order you want to cancel
2. Signing the order hash with your private key
3. Sending the signed cancellation via WebSocket

### Cancel Request Parameters

| Parameter    | Type   | Description                     |
| ------------ | ------ | ------------------------------- |
| `order_hash` | string | The hash of the order to cancel |
| `v`          | number | Signature recovery parameter    |
| `r`          | string | Signature r component           |
| `s`          | string | Signature s component           |

### JavaScript/TypeScript Example

```typescript
import Web3 from 'web3';

async function cancelOrder(privateKey: string, orderHash: string) {
    const web3 = new Web3();
    
    // Sign the order hash
    const signedData = web3.eth.accounts.sign(orderHash, privateKey);
    const signature = signedData.signature;

    // Parse signature into v, r, s
    const sig = signature.slice(2);
    const r = `0x${sig.slice(0, 64)}`;
    const s = `0x${sig.slice(64, 128)}`;
    let v = parseInt(`0x${sig.slice(128, 130)}`, 16);
    if (v < 27) v += 27;

    return {
        order_hash: orderHash,
        v: v,
        r: r,
        s: s
    };
}

// Send cancel request via WebSocket
function sendCancelOrder(ws: WebSocket, cancelRequest: object) {
    const message = JSON.stringify({
        op: 'cancel_order',
        data: cancelRequest
    });
    ws.send(message);
}

// Usage Example
async function main() {
    const privateKey = '0x...'; // Your private key
    const orderHash = '0x...';  // Hash of order to cancel
    
    const cancelRequest = await cancelOrder(privateKey, orderHash);

    const ws = new WebSocket('wss://api.dmex.app/ws');
    
    ws.onopen = () => {
        sendCancelOrder(ws, cancelRequest);
    };

    ws.onmessage = (event) => {
        const response = JSON.parse(event.data);
        console.log('Response:', response);
    };
}
```

### Python Example

```python
import json
import websocket
from web3 import Web3
from eth_account.messages import encode_defunct

def cancel_order(private_key: str, order_hash: str):
    w3 = Web3()
    
    # Sign the order hash
    signed = w3.eth.account.sign_message(
        encode_defunct(hexstr=order_hash),
        private_key=private_key
    )
    
    return {
        'order_hash': order_hash,
        'v': signed.v,
        'r': hex(signed.r),
        's': hex(signed.s)
    }


def send_cancel_order(ws, cancel_request):
    message = json.dumps({
        'op': 'cancel_order',
        'data': cancel_request
    })
    ws.send(message)


# Usage Example
if __name__ == '__main__':
    private_key = '0x...'  # Your private key
    order_hash = '0x...'   # Hash of order to cancel
    
    cancel_request = cancel_order(private_key, order_hash)

    ws = websocket.create_connection('wss://api.dmex.app/ws')
    send_cancel_order(ws, cancel_request)
    
    response = ws.recv()
    print('Response:', response)
    ws.close()
```

### Notes

* You can only cancel orders that you created (signature must match the original order creator)
* The order must still be open (not fully filled or already cancelled)
* To cancel and replace an order atomically, use the `replace_hash` parameter when creating a new order instead


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.dmex.app/api-docs/websocket/cancel-order.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.