Network.framework UDP requiredLocalEndpoint/allowLocalEndpointReuse still broken in macOS 26

Question

Created Jun ’25

Replies 2

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Participants 2

Just tried to re-run the code below (previously discussed https://developer.apple.com/forums/thread/747815) and filed as bug: https://feedbackassistant.apple.com/feedback/13678278

Still broken on macOS 26 first beta.

Any chance anything can be done about this @eskimo?

thanks, Martin

import Foundation
import Network
 
let localPort: NWEndpoint.Port = 12345
 
var connections: [NWConnection] = []
 
func startFlow(remotePort: UInt16) {
    let params = NWParameters.udp
    params.allowLocalEndpointReuse = true
    params.requiredLocalEndpoint = NWEndpoint.hostPort(host: "0.0.0.0", port: localPort)
    let conn = NWConnection(host: "93.184.216.34", port: .init(rawValue: remotePort)!, using: params)
    conn.stateUpdateHandler = { newState in
        print("connection \(remotePort) did change state, new: \(newState)")
    }
    conn.start(queue: .main)
    connections.append(conn)
}
 
func main() {
    startFlow(remotePort: 23456)
    startFlow(remotePort: 23457)
    dispatchMain()
}
 
main()

Boost

Answer 1

DTS Engineer OP

Apple

Jun ’25

Recommended

Still broken on macOS 26 first beta.

Yep. That matches my expectations based on the state of FB13678278.

I recommend that you update your bug with the latest findings. Also, if this issue is having a significant impact on your product, I recommend that you add a summary of that impact to your bug report.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

1

Answer 2

enodev OP

Jun ’25

Thanks @eskimo1. If I am not mistaken the inability to reuse local port for multiple outgoing UDP NWConnections makes it impossible to perform effective STUN and setup peer to peer connections using UDP hole punching techniques. Of course we still have NAT PMP and UPNP. I wonder if FaceTime uses Network.framework how they handle this.

thanks for all your help, Martin

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