NWConnection SSDP Discovery not receiving data

Question

I'm trying to do an SSDP Discovery broadcast and unable to get reply data from NWConnection.receive.

Network.framework is relatively new and there is not a lot of info out there. What I'm missing here?

SSDP Discovery broadcast was sent and a UPnP device replied. (Wireshark screenshot below)

    import Foundation
    import Network

    let connection = NWConnection(host: "239.255.255.250", port: 1_900, using: .udp)

    func sendBroadcast() {
        let message = """
            M-SEARCH * HTTP/1.1
            ST: ssdp:all
            HOST: 239.255.255.250:1900
            MAN: ssdp:discover
            MX: 1
            """.data(using: .utf8)

        connection.send(content: message, completion: .contentProcessed { error in
                if let error = error {
                    print("Send Error: \(error)")
                } else {
                    print("Broadcast sent")
                }
            }
        )
    }

    connection.stateUpdateHandler = { newState in
        switch newState {
        case .setup:
            print("Connection: Setup")
        case .preparing:
             print("Connection: Preparing")
        case .waiting:
            print("Connection: Waiting")
        case .ready:
            print("Connection: Ready")
            sendBroadcast()
        case .failed:
            print("Connection: Failed")
        case .cancelled:
            print("Connection: Cancelled")
        }
    }

    connection.receive(minimumIncompleteLength: 2, maximumLength: 4_096) { data, context, isComplete, error in
        /// This is never executed
        ///
        print(data ?? "", context ?? "", isComplete, error ?? "")
    }

    connection.viabilityUpdateHandler = { update in
        print(update)
    }

    connection.betterPathUpdateHandler = { path in
        print(path)
    }

    connection.start(queue: .main)

    RunLoop.main.run()

Thanks for the NWconnection example, even if this one doesn’t work. It looks like NWconnection programming is going to be easier than CFnetwork once we get used to it. — Darrell Root

Alex Alex · Accepted Answer · 2019-02-15T21:15:05

Turns out Network.framework does not support UDP Broadcasts yet (Feb 2019) https://forums.developer.apple.com/message/316357#316357

NWConnection SSDP Discovery not receiving data

2 Answers