CocoaAsyncSocket: Error creating iOS UDP socket when dispatch_sync(socketQueue, block) is called

Question

I would like to write an iOS Swift app that connects to an UDP server locally.

Here is the code I wrote using a library called CocoaAsyncSocket, however when I run it it does crash.

I haven't found any similar high level API in Apple. The only thing I found is this documentation which suggest to us a higher level API.

Would you be able to point me towards a better library or towards resolving the bug I get?

import UIKit
import CocoaAsyncSocket

class OutputSocket: NSObject, GCDAsyncUdpSocketDelegate {

    var serverIP = "127.0.0.1"
    var port:UInt16 = 10000
    var socket:GCDAsyncUdpSocket!

    override init(){
        super.init()
        setupConnection()
    }

    func setupConnection(){
        socket = GCDAsyncUdpSocket(delegate: self, delegateQueue: DispatchQueue.main)

        do {
            try socket.bind(toPort: self.port)
        }
        catch {
             print("binding error: ", error.localizedDescription)
        }

        let addressData = serverIP.data(using: String.Encoding.utf8)

        do {
            try socket.connect(toAddress: addressData!)}
        catch
        {
            print("connecting error: ", error.localizedDescription)
        }

        do {
            try socket.beginReceiving()
        }
        catch {
            print("connecting error: ", error.localizedDescription)
        }
    }

    func send(message:String){
        let data = message.data(using: String.Encoding.utf8)
        let addressData = serverIP.data(using: String.Encoding.utf8)
        socket.send(data!, toAddress: addressData!, withTimeout: 2, tag: 0)
    }

    func udpSocket(_ sock: GCDAsyncUdpSocket, didConnectToAddress address: Data) {
        print("didConnectToAddress");
    }

    func udpSocket(_ sock: GCDAsyncUdpSocket, didNotConnect error: Error?) {
        print("didNotConnect \(error)")
    }

    func udpSocket(_ sock: GCDAsyncUdpSocket, didSendDataWithTag tag: Int) {
        print("didSendDataWithTag")
    }

    func udpSocket(_ sock: GCDAsyncUdpSocket!, didNotSendDataWithTag tag: Int, dueToError error: Error!) {
        print("didNotSendDataWithTag")
    }
}

---

Error description:

When I run it it crashes here:

EDIT:

I have removed the IP address from the equation and now, when I run the following code I get "didNotSendDataWithTag":

    let data = message.data(using: String.Encoding.utf8)
    socket.send(data!, withTimeout: 2, tag: 0)

Any idea why?