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

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

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