Develop Reference

Get IP address from hostname in LAN

I found many samples on how to get a hostname by an IP address, how can I get the IP address of a host in the LAN?

Try this
public static void DoGetHostAddresses(string hostname)
{
IPAddress[] ips;
ips = Dns.GetHostAddresses(hostname);
Console.WriteLine("GetHostAddresses({0}) returns:", hostname);
foreach (IPAddress ip in ips)
{
Console.WriteLine(" {0}", ip);
}
}
i got this from http://msdn.microsoft.com/en-us/library/system.net.dns.gethostaddresses.aspx

Here is simple code if you want to get the IP Address(V4) from your pc.
Import this library into your class
using System.Net;
Initialize and declare these variables into your codes. They contain hostname, ipaddress and an array of Host Addresses:
string HostName = Dns.GetHostName().ToString();
IPAddress[] IpInHostAddress = Dns.GetHostAddresses(HostName);
string IPV4Address = IpInHostAddress[1].ToString(); //Default IPV4Address. This might be the ip address you need to retrieve
string IPV6Address = IpInHostAddress[0].ToString(); //Default Link local IPv6 Address
Open your command prompt, just type "ipconfig" and press enter.Once you are done, you could check if the string IPV4Address matches to IPv4Address in our pc.

As long as you know the name of a machine, you can use Dns.GetHostAddresses. Your network DNS should recognize it as LAN computer and return proper IP.

Use Dns.GetHostEntry(hostname) instead of obsolete Dns.GetHostAddresses.

Here is an excellent example of how it is doing: http://www.codeproject.com/Articles/854/How-To-Get-IP-Address-Of-A-Machine

you could use the windows management classes to do this, it also works for remote machines that are in the same domain (but I don't know if they need to enable or disable any security or policy settings for this to work). for example:
public List<NetworkAdapter> GetAdapterList()
{
ManagementClass mgmt = new ManagementClass("Win32_NetworkAdapterConfiguration ");
ManagementObjectCollection moc = mgmt.GetInstances();
List<NetworkAdapter> adapters = new List<NetworkAdapter>();
// Search for adapters with IP addresses
foreach(ManagementObject mob in moc)
{
string[] addresses = (string[])mob.Properties["IPAddress"].Value;
if (null == addresses)
{
continue;
}
NetworkAdapter na = new NetworkAdapter();
na.Description = (string) mob.Properties["Description"].Value;
na.MacAddress = (string) mob.Properties["MACAddress"].Value;
na.IPAddresses = addresses;
adapters.Add(na);
}
return adapters;
}
and to access a remote machine create the management class like this instead:
ManagementClass mgmt = new ManagementClass
(\\\\servername\\root\\cimv2:Win32_NetworkAdapterConfiguration);
this approach may get you more IPs than just the ones that have been registered in the DNS.

Get closest Domain Controller in current AD site without hard coding information

For instances when Active Directory takes too long to replicate data between sites, I need to ensure that the local AD replica contains the most up to date information.
How can I get a list of DomainControllers for the current site?
I haven't found anything on Codeproject or on StackOverflow

Going to all this trouble is probably wasted effort. Unless you are experiencing issues with the built in logic for finding a domain controller you should just go with the built in method that returns one. According to Microsoft it automatically tries to find the closes one: http://technet.microsoft.com/en-us/library/cc978016.aspx.
Just use the static DomainController.FindOne method and pass in your directorycontext.
Update
Alright, try the code below, let me know how it works for you. It pings each, returns the roundtrip time, if -1 (no connection) it skips it. Flags PDC status if present. Orders by PDC status, followed by ping round trip.
static void Main(string[] args)
{
var dcsInOrder = (from DomainController c in Domain.GetCurrentDomain().DomainControllers
let responseTime = Pinger(c.Name)
where responseTime >=0
let pdcStatus = c.Roles.Contains(ActiveDirectoryRole.PdcRole)
orderby pdcStatus, responseTime
select new {DC = c, ResponseTime = responseTime}
).ToList();
foreach (var dc in dcsInOrder)
{
System.Console.WriteLine(dc.DC.Name + " - " + dc.ResponseTime);
}
System.Console.ReadLine();
}
private static int Pinger(string address)
{
Ping p = new Ping();
try
{
PingReply reply = p.Send(address, 3000);
if (reply.Status == IPStatus.Success) return (int)reply.RoundtripTime;
}
catch { }
return -1;
}

First, I'll answer the question that you actually asked:
System.DirectoryServices.ActiveDirectory.ActiveDirectorySite.GetComputerSite().Servers
But it seems like you're asking how to make sure that you're talking to the closest domain controller possible. Windows doesn't exactly provide this functionality, the best it will do is give you a domain controller in the same site that the code is running from.
I think the first thing to check is that you have your sites and subnets configured correctly. Run Active Directory Sites and Services, and make sure that subnets and domain controllers are assigned to the correct sites.
This MSDN page (and the Technet article in Peter's answer) says that you must be searching by the DNS name for the DC Locator to attempt to find a DC in the current site. I don't know if the Name property of the Domain class is the DNS domain name.
I have to assume that DomainController.FindOne is a wrapper for DsGetDcName. At that link, you can find how to turn on tracing for that function. You can use this if you still have problems, or maybe you should just PInvoke this function.

Here is a code sample that has no hard coding of DCs. Comments and criticism are welcome.
/// <summary>
/// For best results ensure all hosts are pingable, and turned on.
/// </summary>
/// <returns>An ordered list of DCs with the PDCE first</returns>
static LinkedList<DomainController> GetNearbyDCs()
{
LinkedList<DomainController> preferredDCs = new LinkedList<DomainController>();
List<string> TestedDCs = new List<string>();
using (var mysite = ActiveDirectorySite.GetComputerSite())
{
using (var currentDomain = Domain.GetCurrentDomain())
{
DirectoryContext dctx = new DirectoryContext(DirectoryContextType.Domain, currentDomain.Name);
var listOfDCs = DomainController.FindAll(dctx, mysite.Name);
foreach (DomainController item in listOfDCs)
{
Console.WriteLine(item.Name );
if (IsConnected(item.IPAddress))
{
// Enumerating "Roles" will cause the object to bind to the server
ActiveDirectoryRoleCollection rollColl = item.Roles;
if (rollColl.Count > 0)
{
foreach (ActiveDirectoryRole roleItem in rollColl)
{
if (!TestedDCs.Contains(item.Name))
{
TestedDCs.Add(item.Name);
if (roleItem == ActiveDirectoryRole.PdcRole)
{
preferredDCs.AddFirst(item);
break;
}
else
{
if (preferredDCs.Count > 0)
{
var tmp = preferredDCs.First;
preferredDCs.AddBefore(tmp, item);
}
else
{
preferredDCs.AddFirst(item);
}
break;
}
}
}
}
else
{
// The DC exists but has no roles
TestedDCs.Add(item.Name);
if (preferredDCs.Count > 0)
{
var tmp = preferredDCs.First;
preferredDCs.AddBefore(tmp, item);
}
else
{
preferredDCs.AddFirst(item);
}
}
}
else
{
preferredDCs.AddLast(item);
}
}
}
}
return preferredDCs;
}
static bool IsConnected(string hostToPing)
{
string pingurl = string.Format("{0}", hostToPing);
string host = pingurl;
bool result = false;
Ping p = new Ping();
try
{
PingReply reply = p.Send(host, 3000);
if (reply.Status == IPStatus.Success)
return true;
}
catch { }
return result;
}

Here's my approach using powershell but I'm sure it's a simple implementation in c#, etc. If DHCP is setup correctly, the Primary DNS server in your subnet should be the closest Domain Controller. So the following code should grab the first DNS IP and resolve it to the hostname of the closest DC. This doesn't require RSAT or credentials and contains no specific properties of the current domain.
$NetItems = #(Get-WmiObject -Class Win32_NetworkAdapterConfiguration -Filter "IPEnabled = 'True'" -ComputerName $env:COMPUTERNAME)
foreach ($objItem in $NetItems)
{
if ($objItem.{DNSServerSearchOrder}.Count -ge 1)
{
$PrimaryDNS = $objItem.DNSServerSearchOrder[0]
$domain = $objItem.DNSDomain
break
}
}
[System.Net.Dns]::GetHostbyAddress($PrimaryDNS).hostname -replace ".$($domain)",""

Checking that a user has correctly entered an IP Address

I am currently working on a C# project where I need to validate the text that a user has entered into a text box.
One of the validations required is that it checks to ensure that an IP address has been entered correctly.
How would I go about doing this validation of the IP address.
Thanks for any help you can provide.

You can use IPAddress.Parse Method .NET Framework 1.1. Or, if you are using .NET 4.0, see documentation for IPAddress.TryParse Method .NET Framework 4.
This method determines if the contents of a string represent a valid IP address. In .NET 1.1, the return value is the IP address. In .NET 4.0, the return value indicates success/failure, and the IP address is returned in the IPAddress passed as an out parameter in the method call.
edit: alright I'll play the game for bounty :) Here's a sample implementation as an extension method, requiring C# 3+ and .NET 4.0:
using System;
using System.Net;
using System.Text.RegularExpressions;
namespace IPValidator
{
class Program
{
static void Main (string[] args)
{
Action<string> TestIP = (ip) => Console.Out.WriteLine (ip + " is valid? " + ip.IsValidIP ());
TestIP ("99");
TestIP ("99.99.99.99");
TestIP ("255.255.255.256");
TestIP ("abc");
TestIP ("192.168.1.1");
}
}
internal static class IpExtensions
{
public static bool IsValidIP (this string address)
{
if (!Regex.IsMatch (address, #"\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b"))
return false;
IPAddress dummy;
return IPAddress.TryParse (address, out dummy);
}
}
}

It seems that you are only concerned with validating IPv4 IP Address strings in X.X.X.X format. If so, this code is straight forward for that task:
string ip = "127.0.0.1";
string[] parts = ip.Split('.');
if (parts.Length < 4)
{
// not a IPv4 string in X.X.X.X format
}
else
{
foreach(string part in parts)
{
byte checkPart = 0;
if (!byte.TryParse(part, out checkPart))
{
// not a valid IPv4 string in X.X.X.X format
}
}
// it is a valid IPv4 string in X.X.X.X format
}

If you want to see if the IP address actually exists, you can use the Ping class.

insta's answer was closer before he added the incorrect regexp.
public static bool IsValidIP(string ipAddress)
{
IPAddress unused;
return IPAddress.TryParse(ipAddress, out unused);
}
Or since the OP doesn't want to include integer IPv4 addresses that aren't full dotted quads:
public static bool IsValidIP(string ipAddress)
{
IPAddress unused;
return IPAddress.TryParse(ipAddress, out unused)
&&
(
unused.AddressFamily != AddressFamily.InterNetwork
||
ipAddress.Count(c => c == '.') == 3
);
}
Testing:
IsValidIP("fe80::202:b3ff:fe1e:8329") returns true (correct).
IsValidIP("127.0.0.1") returns true (correct).
IsValidIP("What's an IP address?") returns false (correct).
IsValidIP("127") returns true with first version, false with second (correct).
IsValidIP("127.0") returns true with first version, false with second (correct).

I'd use a regex.
^((25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)\.){3}(25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)$
Using named groups, it could be clearer. It is written in Ruby. I don't know C# but I guess that the regex support is complete in that language and that named groups might exist.
/(?<number>(25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)){0}^(\g<number>\.){3}\g<number>$/

Here's my solution:
using System.Net.NetworkInformation;
using System.Net;
/// <summary>
/// Return true if the IP address is valid.
/// </summary>
/// <param name="address"></param>
/// <returns></returns>
public bool TestIpAddress (string address)
{
PingReply reply;
Ping pingSender = new Ping ();
try
{
reply = pingSender.Send (address);
}
catch (Exception)
{
return false;
}
return reply.Status == IPStatus.Success;
}

IPAddress.Parse() using port on IPv4

I'm trying to parse a string containing an IP address and a port using IPAddress.Parse. This works well with IPv6 addresses but not with IPv4 addresses. Can somone explain why this happens?
The code I'm using is:
IPAddress.Parse("[::1]:5"); //Valid
IPAddress.Parse("127.0.0.1:5"); //null

Uri url;
IPAddress ip;
if (Uri.TryCreate(String.Format("http://{0}", "127.0.0.1:5"), UriKind.Absolute, out url) &&
IPAddress.TryParse(url.Host, out ip))
{
IPEndPoint endPoint = new IPEndPoint(ip, url.Port);
}

This happens because the port is not part of the IP address. It belongs to TCP/UDP, and you'll have to strip it out first. The Uri class might be helpful for this.

IPAddress is not IP+Port. You want IPEndPoint.
Example from http://www.java2s.com/Code/CSharp/Network/ParseHostString.htm
public static void ParseHostString(string hostString, ref string hostName, ref int port)
{
hostName = hostString;
if (hostString.Contains(":"))
{
string[] hostParts = hostString.Split(':');
if (hostParts.Length == 2)
{
hostName = hostParts[0];
int.TryParse(hostParts[1], out port);
}
}
}
Edit: Ok, I'll admit that wasn't the most elegant solution. Try this one I wrote (just for you) instead:
// You need to include some usings:
using System.Text.RegularExpressions;
using System.Net;
// Then this code (static is not required):
private static Regex hostPortMatch = new Regex(#"^(?<ip>(?:\[[\da-fA-F:]+\])|(?:\d{1,3}\.){3}\d{1,3})(?::(?<port>\d+))?$", System.Text.RegularExpressions.RegexOptions.Compiled);
public static IPEndPoint ParseHostPort(string hostPort)
{
Match match = hostPortMatch.Match(hostPort);
if (!match.Success)
return null;
return new IPEndPoint(IPAddress.Parse(match.Groups["ip"].Value), int.Parse(match.Groups["port"].Value));
}
Note that this one ONLY accepts IP address, not hostname. If you want to support hostname you'll either have to resolve it to IP or not use IPAddress/IPEndPoint.

IPAddress.Parse is meant to take A string that contains an IP address in dotted-quad notation for IPv4 and in colon-hexadecimal notation for IPv6. So your first example works for IPv6 and your second example fails because it doesnt support a port for IPv4. Link http://msdn.microsoft.com/en-us/library/system.net.ipaddress.parse.aspx

As Tedd Hansen pointed out, what you are trying to parse is not an IP address but an IP endpoint (IP address + port). And since .NET Core 3.0, you can use IPEndPoint.TryParse to parse a string as an IPEndPoint:
if (IPEndPoint.TryParse("127.0.0.1:5", out IPEndPoint endpoint))
{
// parsed successfully, you can use the "endpoint" variable
Console.WriteLine(endpoint.Address.ToString()); // writes "127.0.0.1"
Console.WriteLine(endpoint.Port.ToString()); // writes "5"
}
else
{
// failed to parse
}

If you work on older versions of .net you can take IPEndPoint.Parse implementation from open source: https://github.com/dotnet/runtime/blob/main/src/libraries/System.Net.Primitives/src/System/Net/IPEndPoint.cs

To add my two cents... Since Microsoft itself implemented TryParse in NET Core 3.0 I've opted to stop using my custom IP+Port parser and kindly borrowed their code with some adaptations:
public static class IPEndPointParserExtension
{
public static bool TryParseAsIPEndPoint(this string s, out IPEndPoint result) {
#if NETCOREAPP3_0_OR_GREATER
return IPEndPoint.TryParse(s, out result);
#else
int addressLength = s.Length; // If there's no port then send the entire string to the address parser
int lastColonPos = s.LastIndexOf(':');
// Look to see if this is an IPv6 address with a port.
if (lastColonPos > 0) {
if (s[lastColonPos - 1] == ']')
addressLength = lastColonPos;
// Look to see if this is IPv4 with a port (IPv6 will have another colon)
else if (s.Substring(0, lastColonPos).LastIndexOf(':') == -1)
addressLength = lastColonPos;
}
if (IPAddress.TryParse(s.Substring(0, addressLength), out IPAddress address)) {
long port = 0;
if (addressLength == s.Length ||
(long.TryParse(s.Substring(addressLength + 1), out port)
&& port <= IPEndPoint.MaxPort)) {
result = new IPEndPoint(address, (int)port);
return true;
}
}
result = null;
return false;
#endif
}
public static IPEndPoint AsIPEndPoint(this string s) =>
s.TryParseAsIPEndPoint(out var endpoint)
? endpoint
: throw new FormatException($"'{s}' is not a valid IP Endpoint");
}
My changes were to basically exchange Span<char> for string and make it an extension method of the class String itself. I've also conditionally compile to use Microsoft's implementation if it is available (NET Core 3.0 or greater).
The following nUnit tests show how to use the code:
[Test]
public void CanParseIpv4WithPort() {
var sIp = "192.168.0.233:8080";
if (sIp.TryParseAsIPEndPoint(out var endpoint)) {
var expected = new IPEndPoint(new IPAddress(new byte[] { 192, 168, 0, 233 }), 8080);
Assert.AreEqual(expected, endpoint);
} else
Assert.Fail($"Failed to parse {sIp}");
}
[Test]
public void CanParseIpv6WithPort() {
var sIp = "[2001:db8:85a3:8d3:1319:8a2e:370:7348]:443";
if (sIp.TryParseAsIPEndPoint(out var endpoint)) {
var expected = new IPEndPoint(IPAddress.Parse("2001:db8:85a3:8d3:1319:8a2e:370:7348"), 443);
Assert.AreEqual(expected, endpoint);
} else
Assert.Fail($"Failed to parse {sIp}");
}
You can also use AsIpEndPoint which will throw an exception if it fails to parse the IP address and port (port is optional):
var ep = "127.0.0.1:9000".AsIPEndPoint();

Get IP of my machine C# with virtual machine installed

I want to get the current IP address of the computer that has say 3 virtual machines (VM Ware) installed. I want to get LAN address of that computer.
current code that i have returns me an array but how to identify current computer lan address ?
public static string getThisCompIPAddress()
{
IPAddress[] addresslist = Dns.GetHostAddresses(Dns.GetHostName());
return (addresslist[0].ToString());
}
addresslist returns an array of 3 IP addresses

You could try the NetworkInterface class, and try to match the name or physical address of the LAN connection to find out the real one. Maybe searching within this class and it's members you can find something that suits your needs.
Here is a simple method to provide some usage info:
using System.Net.NetworkInformation;
...
static void ViewNetworkInfo()
{
NetworkInterface[] networks = NetworkInterface.GetAllNetworkInterfaces();
foreach (NetworkInterface nw in networks)
{
Console.WriteLine(nw.Name);
Console.WriteLine(nw.GetPhysicalAddress().ToString());
IPInterfaceProperties ipProps = nw.GetIPProperties();
foreach (UnicastIPAddressInformation ucip in ipProps.UnicastAddresses)
{
Console.WriteLine(ucip.Address.ToString());
}
Console.WriteLine();
}
Console.ReadKey();
}

I've tried all of the solutions above but couldn't get the ip from my "real" machine and not the virtual one. I've managed to use this to get the IP from my virtual machine:
IPAddress[] addresslist = Dns.GetHostAddresses(Environment.ExpandEnvironmentVariables("%CLIENTNAME%"));
The reason why I used it this way is that the function Dns.GetHostAddresses return the adresses of the given host, so if you use the Dns.GetHostName() function it will return the virtual-machine name and not the local machine, but using the name of the machine where you can find using the: Environment.ExpandEnvironmentVariables("%CLIENTNAME%") you can get the client name and not the virtual-machine name, this way you can get the real IP of your local machine.
I hope this helps.

public static ArrayList getThisCompIPAddress()
{
ArrayList strArrIpAdrs = new ArrayList();
ArrayList srtIPAdrsToReturn = new ArrayList();
addresslist = Dns.GetHostAddresses(Dns.GetHostName());
for (int i = 0; i < addresslist.Length; i++)
{
try
{
long ip = addresslist[i].Address;
strArrIpAdrs.Add(addresslist[i]);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
foreach (IPAddress ipad in strArrIpAdrs)
{
lastIndexOfDot = ipad.ToString().LastIndexOf('.');
substring = ipad.ToString().Substring(0, ++lastIndexOfDot);
if (!(srtIPAdrsToReturn.Contains(substring)) && !(substring.Equals("")))
{
srtIPAdrsToReturn.Add(substring);
}
}
return srtIPAdrsToReturn;
}
this is 100% working, the real problem was that it was throwing error while calculating Address that returns long. Error Code is 10045