NWConnection issues on iOS 12.2.

I'm implementing UDP based iOS app and using Network framework to do actual communication to remote server. I'm seeing quite a few abnormalities with iOS12.2 which are outlined below:

a) Type of dispatch queue set in NWConnection.start(): It wasn't clear if queue should be serial or even concurrent queue is also fine. nwcat example uses main queue which is serial but wondering whether concurrent queue works as well to speed up things little bit.

On iOS 12.2, when I use concurrent queue, I see that there are two calls to completion handler in quick sucession for `ready` state but there is only one call if I instead use serial queue.

Above behavior is only seen starting with iOS 12.2 and there is always only one call to completion handler for `ready` state on iOS 12.1.1 irrespective of whether serial or concurrent queue is used.

b) UDP datagram size in NWConnection.receive(): Might be related to above but when I invoke NWConnection.receive() after connection state is set to `ready`, I see data size much higher than underlying datagram sizes received by the interface. I verified with wireshark that each datagram is around 1500 bytes with no fragmentation involved while I see datagram size to be around 2500 in some instances in the completion handler.

Isn't data in NWConnection.receive() completion handler at datagram granularity or is it based on available received data irrespective of datagrams? It is at datagram granularity in Network.Extension framework so wondering if it is any different in Network framework.

Sample code below. Line 10 gets called twice on iOS 12.2 with concurrent queue used for NWConnection while it only gets called once in iOS 12.1.1 irrespective of queue type.

    private func setupStateHandler() {
        connection.stateUpdateHandler = { [weak self] (state) in
            guard let strongSelf = self else {
                return
            }

            switch state {
            case .ready:
                strongSelf.canSendAndReceive = true
                strongSelf.receiveDatagrams()
            default:
                strongSelf.canSendAndReceive = false
            }
        }
    }

    private func receiveDatagrams() {
        connection.receive(minimumIncompleteLength: 1, maximumLength: Int(INT32_MAX), completion: { (data, _, isComplete, error) in
            if error != nil {
                return
            }

            if let validData = data, isComplete {
                self.delegate?.didReceiveDatagrams(datagrams: [validData])
            }

            self.receiveDatagrams()
        })
    }