Resolve HostName to IP

Question

I have been through a lot of googling for this, I found a lot of examples none of which was working for me. This is a simple issue which I feel has a simple answer without defining new classes\modules etc...

My code is this :

Console.WriteLine ("Please enter an IP address or hostname");
string host = Console.ReadLine ();
***IP = resolved "host"*** 
Socket s = new Socket (AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);    
s.Connect (IP, 80);
s.close();

How do I actually resolve the IP variable?

your question is lacking a question. What is your actual issue? Do you get any exceptions? Are you having issues parsing an IP? — default, Nov 06 '12 at 10:24
http://stackoverflow.com/questions/3256452/get-host-name-from-ip-address might help you — indiPy, Nov 06 '12 at 10:25
I edited to make it a little more clear what the question is — Ba7a7chy, Nov 06 '12 at 10:38

Kolja · Accepted Answer · 2012-11-06T10:39:07.813

98

You can simply use the DNS class to do so:

IPHostEntry hostEntry;

hostEntry= Dns.GetHostEntry(host);

//you might get more than one ip for a hostname since 
//DNS supports more than one record

if (hostEntry.AddressList.Length > 0)
{
      var ip = hostEntry.AddressList[0];
      Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
      s.Connect(ip, 80);
}

edited Nov 06 '12 at 10:39

answered Nov 06 '12 at 10:26

Kolja

2,307
15
23

This gives me : "the best overloaded methoud match for system.net.sockets.socket.connect(system.net.ipaddress, int) has some invalid arguments Argument #1 cannot convert system.net.iphostentry to type system.net.ipaddress – Ba7a7chy Nov 06 '12 at 10:34

score 39 · Answer 2 · answered Nov 06 '12 at 10:27

39

string howtogeek = "www.howtogeek.com";
IPAddress[] addresslist = Dns.GetHostAddresses(howtogeek);

foreach (IPAddress theaddress in addresslist)
{
   Console.WriteLine(theaddress.ToString());
 }

from howtogeek

answered Nov 06 '12 at 10:27

indiPy

7,844
3
28
39

1

This is the better answer if you want to take a string that could be either hostname or an IP address and get back a list of IP addresses. If you use GetHostEntry() from the accepted answer instead of GetHostAddresses(), providing a string that is already an IP address will still result in a DNS lookup to fill in the other information for the entry. – Andrew Bennett May 19 '22 at 18:19

score 11 · Answer 3 · answered Jun 30 '18 at 07:23

Please take the note that accepted answer can resolve to IPv6. I attempted to connect to service that does not accept IPv6 as input string.

Therefore try this snippet if you care to get IPv4:

using System.Linq;

string host = "google.com";

Dns.GetHostEntry(host).AddressList.First(addr => addr.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)

score 3 · Answer 4 · answered May 16 '20 at 20:55

This is the method I use to resolve a hostname to IPv4 and / or IPv6.

    using System.Net:

    // A host can have multiple IP addresses!
    public static IPAddress[] GetIPsByName(string hostName, bool ip4Wanted, bool ip6Wanted)
    {
        // Check if the hostname is already an IPAddress
        IPAddress outIpAddress;
        if (IPAddress.TryParse(hostName, out outIpAddress) == true)
            return new IPAddress[] { outIpAddress };
        //<----------

        IPAddress[] addresslist = Dns.GetHostAddresses(hostName);

        if (addresslist == null || addresslist.Length == 0)
            return new IPAddress[0];
        //<----------

        if (ip4Wanted && ip6Wanted)
            return addresslist;
        //<----------

        if (ip4Wanted)
            return addresslist.Where(o => o.AddressFamily == AddressFamily.InterNetwork).ToArray();
        //<----------

        if (ip6Wanted)
            return addresslist.Where(o => o.AddressFamily == AddressFamily.InterNetworkV6).ToArray();
        //<----------

        return new IPAddress[0];
    }

1

I like your answer a lot. – IneedHelp Nov 27 '20 at 09:42

score 2 · Answer 5 · answered May 19 '22 at 18:27

If all you want is to resolve a string that could represent either a hostname OR an IP address, you probably want to use System.Net.Dns.GetHostAddresses() rather than System.Net.Dns.GetHostEntry().

GetHostAddresses() skips the DNS lookup if the string parses to an IP address already, while GetHostEntry() will do a reverse lookup for the hostname.

https://learn.microsoft.com/en-us/dotnet/api/system.net.dns.gethostaddresses

score -3 · Answer 6 · answered May 18 '21 at 10:59

-3

The IpAddress has the appropriate method for parsing hostname to IpAddress.

IPAddress addr = IPAddress.Parse(hostName)

answered May 18 '21 at 10:59

Рашид Кашапов

5
1

2

This does not resolve the IP address from the host name. This will only create an `IPAddress` instance when `hostName` is a string in valid IPv4 or IPv6 format, which does not satisfy the original question. – NanoTree Sep 30 '21 at 15:59

Resolve HostName to IP

6 Answers6

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