NWListener on NWConnection port

I'm struggling to use NWListener and NWConnection on the same port.

I have a simple task requires that I send out a UDP datagram to the broadcast address, and expect to receive replies on the port which sent the datagram. In Blue Sockets, I can create a socket, send out the broadcast message and listen and accept connections on the same socket.

In wireshark the exchange looks like:

10.0.0.123     255.255.255.255     UDP     71          62003 -> 9000 Len=29
10.0.0.202     10.0.0.123          UDP     1060        9000 -> 62003 Len=101

However after hours of experimentation in a swift playground, I am not able to create an NWListener and an NWConnection on the same socket.

Here are the salient pieces of code:

let udpListener = try! NWListener(using: .udp)
... setup and start listener
let broadcast: NWEndpoint.Host = "255.255.255.255"
let portUDP: NWEndpoint.Port = 9000
let localPort : NWEndpoint.Port = udpListener!.port!
let localEndpoint = NWEndpoint.hostPort(host: "10.0.0.123", port: localPort)

let parameters = NWParameters.udp
parameters.requiredLocalEndpoint = localEndpoint

let connection = NWConnection(host: broadcast, port: portUDP, using: parameters)

However creating the NWConnection on the same port as the NWListener gives an error that the port is in use. I've tried the reverse, createing the connection on a known port, closing it and starting a listener immediately affterwards on that same port, but that also results in an error.

How can I implement this very simple protocol using the Network API ? Are there some options I need to set ?

Thanks for any help.

Guy