DNS TXT resolving in Swift5

a-record.swift

let memory = rawData!.bindMemory(to: UInt8.self, capacity: 4)

print(memory[0], memory[1], memory[2], memory[3])
print(ttl, Int(rdlen))

/* ..... */

let error = DNSServiceQueryRecord(
    &service,
    kDNSServiceFlagsTimeout,
    0,
    domainName,
    UInt16(kDNSServiceType_A),
    UInt16(kDNSServiceClass_IN),
    callback,
    nil)

main.swift

//
//  main.swift
//  dns-resolver
//
//  Created by menangen on 11.02.2020.
//  Copyright © 2020 menangen. All rights reserved.
//

import Foundation
import dnssd

let group = DispatchGroup()

let callback: DNSServiceQueryRecordReply = {
    (sdRef, flags, interfaceIndex, errorCode, fullname, rrtype, rrclass, rdlen, rawData, ttl, context) -> Void in
/*
    let data = Data(bytes: rawData!, count: Int(rdlen))
    let str = String(data: data, encoding: String.Encoding.ascii)
*/
    let charPointer = UnsafePointer<CChar>(rawData!.bindMemory(to: CChar.self, capacity: Int(rdlen)))
    let str = String(cString: charPointer, encoding: String.Encoding.ascii)!
    
    print(ttl, str)
    
    group.leave()
}

let concurrentQueue = DispatchQueue(label: "queuename", attributes: .concurrent)

var service: DNSServiceRef?
let domainName = "zoness.novikova.us"

let error = DNSServiceQueryRecord(
    &service,
    kDNSServiceFlagsTimeout,
    0,
    domainName,
    UInt16(kDNSServiceType_TXT),
    UInt16(kDNSServiceClass_IN),
    callback,
    nil)



let fd = DNSServiceRefSockFD(service)
print("Socket created", fd)
let eventSource = DispatchSource.makeReadSource(fileDescriptor: fd, queue: concurrentQueue)


eventSource.setEventHandler {
    print("Event...")
    
    print("DNSServiceProcessResult")
    let res = DNSServiceProcessResult(service)

    if (res != kDNSServiceErr_NoError) { print("There was an error reading the DNS record") }
    
}
eventSource.setCancelHandler {
    print("Cancel")
    
    group.leave()
}

concurrentQueue.asyncAfter(wallDeadline: .now() + 2) { eventSource.cancel() }

group.enter()
eventSource.resume();
group.wait()

DNSServiceRefDeallocate(service)
print("Hello, DNS!")