How to get UDP sender address using Network.framework

Question

damiaan OP

Created Jun ’20

Replies 2

Boosts 0

Views 1.1k

Participants 2

I need to implement a custom discovery protocol using UDP. It works like this:

You broadcast a beacon to a broadcast address (like 255.255.255.255).
You wait for clients that respond to your beacon.

The problem is: how can I get the addresses of the clients once they send their response?

Sending

I sent the beacon like this:

Code Block let connection = NWConnection(
	to: .hostPort(
		host: .ipv4(.broadcast),
		port: .init(integerLiteral: discoveryPort)
	),
	using: .udp
)
connection.start(queue: .main)
connection.send(
	content: beacon,
	completion: .contentProcessed(sendCompleted)
)

Receiving

To receive the responses from the clients I use

Code Block connection.receiveMessage {
	(message: Data?, context: NWConnection.ContentContext?, isComplete: Bool, optionalError: NWError?) in
	// Great I got a response...
	// But how do I know where this is coming from?
}

Boost

Answer 1

Engineer OP

Apple

Jun ’20

In general, the remote side of a connection can be accessed on connection.currentPath.remoteEndpoint.

In the example you give, are you receiving this connection from a UDP NWListener that gets the responses to your broadcast message?

0

Answer 2

damiaan OP

Jun ’20

Hi thanks for the response.
connection.currentPath.remoteEndpoint is the broadcast address in my example.

I didn't use an NWListener, I called receiveMessage on the NWConnection from which I am sending the beacons. I did this because I need to listen to the port from which the beacons are sent.

How do I create a NWListener that binds to the same port my NWConnection uses to send the beacon?

0