How do I determine the local host’s IPv4 addresses?

Question

How do I get only Internet Protocol version 4 addresses from Dns.GetHostAddresses()? I have the code below, and it gives me IPv4 and IPv6 addresses. I have to make it work with boxes that have multiple IPv4 addresses.

IPAddress[] localIPs = Dns.GetHostAddresses(Dns.GetHostName());
private void get_IPs()
    {
        foreach (IPAddress a in localIPs)
        {
           server_ip = server_ip + a.ToString() + "/";
        }
    }

score 36 · Answer 1 · answered Jul 12 '11 at 18:05

From my blog:

/// <summary> 
/// This utility function displays all the IP (v4, not v6) addresses of the local computer. 
/// </summary> 
public static void DisplayIPAddresses() 
{ 
    StringBuilder sb = new StringBuilder(); 

    // Get a list of all network interfaces (usually one per network card, dialup, and VPN connection) 
    NetworkInterface[] networkInterfaces = NetworkInterface.GetAllNetworkInterfaces(); 

    foreach (NetworkInterface network in networkInterfaces) 
    { 
        // Read the IP configuration for each network 
        IPInterfaceProperties properties = network.GetIPProperties(); 

        // Each network interface may have multiple IP addresses 
        foreach (IPAddressInformation address in properties.UnicastAddresses) 
        { 
            // We're only interested in IPv4 addresses for now 
            if (address.Address.AddressFamily != AddressFamily.InterNetwork) 
                continue; 

            // Ignore loopback addresses (e.g., 127.0.0.1) 
            if (IPAddress.IsLoopback(address.Address)) 
                continue; 

            sb.AppendLine(address.Address.ToString() + " (" + network.Name + ")"); 
        } 
    } 

    MessageBox.Show(sb.ToString()); 
}

In particular, I do not recommend Dns.GetHostAddresses(Dns.GetHostName());, regardless of how popular that line is on various articles and blogs.

I was having such a hard time getting correct results with Dns..... This provided me exactly what I was looking for. Thanks — Tsukasa, Jun 13 '13 at 20:03
had trouble before with website hosted in Azure. This however works pretty well, as opposed to the Dns.GetHostAddress method you mentioned — Tudor Carean, Jun 16 '15 at 09:01

score 28 · Accepted Answer · answered Jul 12 '11 at 18:01

28

add something like this to your code

  if( IPAddress.Parse(a).AddressFamily == AddressFamily.InterNetwork )
  // IPv4 address

answered Jul 12 '11 at 18:01

Joost Evertse

1,065
7
8

foreach (IPAddress a in localIPs) { if (a.IsIPv6LinkLocal == false) { server_ip = server_ip + a.ToString() + "/"; } } – John Ryann Jul 12 '11 at 18:35
1

The problem with this is I've received a 169.254.x.x address from this method. – Brain2000 Nov 19 '15 at 23:38

Joe · Answer 3 · 2013-03-05T23:47:36.870

12

Here's a function I use:

public static string GetIP4Address()
{
    string IP4Address = String.Empty;

    foreach (IPAddress IPA in Dns.GetHostAddresses(Dns.GetHostName()))
    {
        if (IPA.AddressFamily == AddressFamily.InterNetwork)
        {
            IP4Address = IPA.ToString();
            break;
        }
    }

    return IP4Address;
}

As an enumerable:

public static IEnumerable<string> GetIP4Addresses()
{
    return Dns.GetHostAddresses(Dns.GetHostName())
        .Where(IPA => IPA.AddressFamily == AddressFamily.InterNetwork)
        .Select(x => x.ToString());
}

edited Mar 05 '13 at 23:47

answered Jul 12 '11 at 18:01

Joe

80,724
18
127
145

1

I would not recommend comparing against a string since this needs a lookup of the enum value via reflection and perform a string comparison. Especially since you can compare against the enum `AddressFamily.InterNetwork` without problem. – Alex Jul 12 '11 at 18:06
This function returns one address, but the question states it must support hosts with multiple IPv4 addresses. – Greg Bacon Mar 05 '13 at 13:57

score 7 · Answer 4 · answered Dec 05 '13 at 02:16

7

Very Clean and sweet when using Linq

IPAddress[] addresses = Dns.GetHostAddresses(Dns.GetHostName()).Where(a => a.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork).ToArray();

answered Dec 05 '13 at 02:16

electricalbah

2,227
2
22
36

score 4 · Answer 5 · answered Jul 12 '11 at 18:00

4

Write locaIPs.Where(ip => ip.AddressFamily == AddressFamily.InterNetwork)

answered Jul 12 '11 at 18:00

SLaks

868,454
176
1,908
1,964

score 4 · Answer 6 · answered Jul 12 '11 at 18:05

From MSDN on Dns.GetHostAddresses,

When an empty string is passed as the host name, this method returns the IPv4 addresses of the local host for all operating systems except Windows Server 2003; for Windows Server 2003, both IPv4 and IPv6 addresses for the local host are returned.

IPv6 addresses are filtered from the results of the GetHostAddresses method if the local computer does not have IPv6 installed. As a result, it is possible to get back an empty IPAddress instance if only IPv6 results where available for the hostNameOrAddress.parameter.

So, you can use this to try and parse it:

IPAddress.TryParse

then check AddressFamily which

Returns System.Net.Sockets.AddressFamily.InterNetwork for IPv4 or System.Net.Sockets.AddressFamily.InterNetworkV6 for IPv6.

string input = "192.168.0.10";

IPAddress address;
if (IPAddress.TryParse(input, out address))
{
    switch (address.AddressFamily)
    {
        case System.Net.Sockets.AddressFamily.InterNetwork:
            // we have IPv4
            break;
        case System.Net.Sockets.AddressFamily.InterNetworkV6:
            // we have IPv6
            break;
        default:
            // do something else
            break;
    }
}

score 1 · Answer 7 · edited Sep 17 '14 at 07:13

I used the answer that started with

/// <summary> and it mostly worked:
//for some reason Visual Studio 2010 did not understand AddressFamily.Inernetwork
    if (address.Address.AddressFamily != AddressFamily.InterNetwork)

I had to use:

if(address.Address.AddressFamily != System.Net.Sockets.AddressFamily.InterNetwork)

but I actually used:

if(!address.Address.AddressFamily.Equals(System.Net.Sockets.AddressFamily.InterNetwork))

Also, I added:

if (network.OperationalStatus != OperationalStatus.Up)
                continue;

Because there were some networks which didn't work and should never have been there, I did see that they were in the registry. ---Alvin

score 0 · Answer 8 · edited Sep 17 '14 at 07:18

0

For me the cleaner solution would be:

 public static string GetLocalIP() 
        {
            string ipv4Address = String.Empty;

            foreach (IPAddress currentIPAddress in Dns.GetHostAddresses(Dns.GetHostName()))
            {
                if (currentIPAddress.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
                {
                    ipv4Address = currentIPAddress.ToString();
                    break;
                }
            }

            return ipv4Address;
        }

edited Sep 17 '14 at 07:18

Farhan S.

698
8
26

answered Aug 30 '12 at 11:04

svives

82
3

This function returns one address, but the question states it must support hosts with multiple IPv4 addresses. – Greg Bacon Mar 05 '13 at 13:57

score 0 · Answer 9 · answered Feb 11 '14 at 23:15

I use this helper method that returns the first active IPV4 address after filtering out the IPV6 and Loopback once


    public static IPAddress GetLocalIPAddress()
    {
        IPAddress result = null;
        IPHostEntry iphostentry = Dns.GetHostEntry(Dns.GetHostName());
        IPAddress[] ipv4Address = Array.FindAll(iphostentry.AddressList, add => add.AddressFamily == AddressFamily.InterNetwork && !IPAddress.IsLoopback(add));
        if (ipv4Address.Length > 0 )
        {
            result =ipv4Address[0];
        }
        return result;
    }

score 0 · Answer 10 · answered Nov 08 '17 at 09:26

This is my code. And can find it on many LAN cards.

private string GetLocalIpAddress()
{
    string localIpAddress = string.Empty;
    NetworkInterface[] nics = NetworkInterface.GetAllNetworkInterfaces();

    foreach (NetworkInterface nic in nics)
    {
        if (nic.OperationalStatus != OperationalStatus.Up)
        {
            continue;
        }

        IPv4InterfaceStatistics adapterStat = (nic).GetIPv4Statistics();
        UnicastIPAddressInformationCollection uniCast = (nic).GetIPProperties().UnicastAddresses;

        if (uniCast != null)
        {
            foreach (UnicastIPAddressInformation uni in uniCast)
            {
                if (adapterStat.UnicastPacketsReceived > 0
                    && adapterStat.UnicastPacketsSent > 0
                    && nic.NetworkInterfaceType != NetworkInterfaceType.Loopback)
                {
                    if (uni.Address.AddressFamily == AddressFamily.InterNetwork)
                    {
                        localIpAddress = nic.GetIPProperties().UnicastAddresses[0].Address.ToString();

                        break;
                    }
                }
            }
        }
    }

    return localIpAddress;
}

score 0 · Answer 11 · answered Feb 13 '19 at 21:30

Here is a code to find the first connected IPv4 by using for loop :

        IPAddress ipAddress = null;
        IPAddress[] localIPs = Dns.GetHostAddresses(Dns.GetHostName());           

        for (int i=0 ; i<localIPs.Length ; i++)
        {
            if (localIPs[i].AddressFamily == AddressFamily.InterNetwork)
            {
                ipAddress = localIPs[i];
                break;
            }                
        }

How do I determine the local host’s IPv4 addresses?

11 Answers11

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