how to make continues api using URLSessionTask - swift

Question

Hi guys below is my code im using at the moment im making a pos system and talk to a merchant and return talks to a pin pad .
the problem i have is that when i do a purchase for the first time it works 100 percent i get a response from the service
. but when i do another purchase and it does the call nothing happens .
im wondering if the task inst done yet . i dont know whats going on any help
only way i can do another call is by restarting the app
func pinPad(Total:Int,echoData:Int64,retrievalReferenceNumber:Int64, cardAcceptorTerminalId:Int64,cardAcceptorIdCode:Int64) -> String
{
getdata()
var status:String = ""
let Message = "<?xml version='1.0' encoding='utf-8'?>"
var is_URL: String = "http://\(ipcon):\(portcon)/merchant/service"
var session = URLSession.shared
var lobj_Request = NSMutableURLRequest(url: NSURL(string: is_URL)! as URL)
var task: URLSessionTask? = nil
var err: NSError?
lobj_Request.httpMethod = "POST"
lobj_Request.httpBody = Message.data(using: String.Encoding.utf8)
lobj_Request.addValue("http://\(ipcon):\(portcon)", forHTTPHeaderField: "Host")
lobj_Request.addValue("text/xml; charset=utf-8", forHTTPHeaderField: "Content-Type")
// lobj_Request.addValue(String(count(Message)), forHTTPHeaderField: "Content-Length")
//lobj_Request.addValue("223", forHTTPHeaderField: "Content-Length")
lobj_Request.addValue("http://\(ipcon):\(portcon)/merchant/service", forHTTPHeaderField: "SOAPAction")
print("helo: \(lobj_Request)")
if nil != task{
task!.cancel()
task = nil
}
let sem = DispatchSemaphore(value: 0)
task = session.dataTask(with: lobj_Request as URLRequest){ data, response, error in
if error != nil{
return
}else{
let strData = NSString(data: (data)!, encoding: String.Encoding.utf8.rawValue) as! String
print("Body: \(strData)")
let xml = SWXMLHash.config {
config in
config.shouldProcessLazily = true
}.parse(strData)
if(xml["S:Envelope"]["S:Body"]["responseCode"].element?.text != nil)
{
status = xml["S:Envelope"]["S:Body"]["responseCode"].element!.text
}
else{
status = xml["S:Envelope"]["S:Body"]["ns2:responseCode"].element!.text
}
sem.signal()
}
}
task?.resume()
sem.wait()
session.invalidateAndCancel()
return status
}