.NET Framework Networking Basic SNTP client (UdpClient)
Example
See RFC 2030 for details on the SNTP protocol.
using System;
using System.Globalization;
using System.Linq;
using System.Net;
using System.Net.Sockets;
class SntpClient
{
const int SntpPort = 123;
static DateTime BaseDate = new DateTime(1900, 1, 1);
static void Main(string[] args)
{
if(args.Length == 0) {
Console.WriteLine("Simple SNTP client");
Console.WriteLine();
Console.WriteLine("Usage: sntpclient <sntp server url> [<local timezone>]");
Console.WriteLine();
Console.WriteLine("<local timezone>: a number between -12 and 12 as hours from UTC");
Console.WriteLine("(append .5 for an extra half an hour)");
return;
}
double localTimeZoneInHours = 0;
if(args.Length > 1)
localTimeZoneInHours = double.Parse(args[1], CultureInfo.InvariantCulture);
var udpClient = new UdpClient();
udpClient.Client.ReceiveTimeout = 5000;
var sntpRequest = new byte[48];
sntpRequest[0] = 0x23; //LI=0 (no warning), VN=4, Mode=3 (client)
udpClient.Send(
dgram: sntpRequest,
bytes: sntpRequest.Length,
hostname: args[0],
port: SntpPort);
byte[] sntpResponse;
try
{
IPEndPoint remoteEndpoint = null;
sntpResponse = udpClient.Receive(ref remoteEndpoint);
}
catch(SocketException)
{
Console.WriteLine("*** No response received from the server");
return;
}
uint numberOfSeconds;
if(BitConverter.IsLittleEndian)
numberOfSeconds = BitConverter.ToUInt32(
sntpResponse.Skip(40).Take(4).Reverse().ToArray()
,0);
else
numberOfSeconds = BitConverter.ToUInt32(sntpResponse, 40);
var date = BaseDate.AddSeconds(numberOfSeconds).AddHours(localTimeZoneInHours);
Console.WriteLine(
$"Current date in server: {date:yyyy-MM-dd HH:mm:ss} UTC{localTimeZoneInHours:+0.#;-0.#;.}");
}
}
