iPhone 的网络时间协议

iPhone网络时间协议：准确同步时间的关键

swift
import Foundation
import Network
func syncDeviceTime() {
    let timeServer = "time.apple.com"
    let ntpPort = 123
    
    let ntpQuery = "0101000000000000000000000000000000000000000000000000000000000000"
    let ntpData = Data(hexString: ntpQuery)
    
    let queue = DispatchQueue(label: "com.example.ntp")
    let ntpEndpoint = NWEndpoint.hostPort(host: NWEndpoint.Host(stringLiteral: timeServer), port: NWEndpoint.Port(integerLiteral: ntpPort))
    
    let connection = NWConnection(to: ntpEndpoint, using: .udp)
    
    connection.stateUpdateHandler = { newState in
        switch newState {
        case .ready:
            connection.send(content: ntpData, completion: .contentProcessed({ error in
                if let error = error {
                    print("Error sending NTP request: \(error)")
                }
            }))
        case .failed(let error):
            print("Connection failed with error: \(error)")
        default:
            break
        }
    }
    
    connection.start(queue: queue)
    
    connection.receiveMessage { data, context, isComplete, error in
        if let data = data, let ntpResponse = data.hexString {
            // 解析ntpResponse并校正设备时钟
            // ...
        }
    }
}
extension Data {
    init?(hexString: String) {
        var hex = hexString.trimmingCharacters(in: .whitespacesAndNewlines)
        var data = Data()
        
        while !hex.isEmpty {
            let subIndex = hex.index(hex.startIndex, offsetBy: 2)
            let subString = String(hex[..            hex = String(hex[subIndex...])
            
            if let byte = UInt8(subString, radix: 16) {
                data.append(byte)
            } else {
                return nil
            }
        }
        
        self = data
    }
    
    var hexString: String? {
        return map { String(format: "%02hhx", $0) }.joined()
    }
}