Asynchronous callback

Precautions

1. After receiving the asynchronous notification, you must respond with an 
 httpResponse status code of 200. All other status codes are regarded as callback
 failures. After the callback fails, You will receive a retry request after a 
 short period of time.
2. The merchant must verify the x-api-signature of the callback notification,
 where the time window offset between x-api-timestamp and the current timestamp 
 needs to be less than 5s.

You must take corresponding actions based on the value of the status field. The value of status may be 2 (completed) or 8 (rejected)

If the order has been successfully called back and still receives a callback request, please ignore it and return HTTPSTATUS:200

Callback request header parameter description

Name	Type	Description
x-api-key	string	apikey
x-api-nonce	string	random string
x-api-timestamp	int(10)	Unix timestamp
x-api-signature	string	Signature Hash value

Callback request body parameter description

Name	Type	Description
sys_trade_no	string	System order number
out_trade_no	string	Merchant order number
assets	string	Assets Type
amount	string	decimal(16,6) to String
exc_rate	string	decimal(16,6) to String
cur_usdt_volume	string	decimal(16,6) to String actual collection amount of USDT
rel_usdt_volume	string	decimal(16,6) to String =cur_usdt_volume
f_rate_payout	string	decimal(16,6) to String percentage fee
g_rate_payout	string	decimal(16,6) to String fixed fee
fee	string	decimal(16,6) to String
from	string	Send address
to	string	Receiving address
status	string	int(1) to String, paid=2
create_time	string	int(10) to String
payfor_time	string	int(10) to String
callbk_time	string	int(10) to String