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Get the computer name instead of the DNS name using IP adress [duplicate]

This question already has answers here:
How do I get the NetBIOS name of a machine from IP in C#?
(5 answers)
Closed 6 months ago.
I have the following code:
public static string GetHostname(string sIP) {
// GetServerIP(sIP)[0] is the IP of the server
string? sHostname = GetServerIP(sIP)[0];
IPHostEntry host = Dns.GetHostEntry(sHostname);
return host.HostName.ToString()!;
}
The ip address is correct but the name returned is not (in my case) "server" but "MeinServer.speedport.ip", which is odd because the server has a static ip address. The name returned is the one used by the router.
When I use ping in cmd with the IP I get the correct name, so why not with the function?
How do I get the correct computer name and not the dns name of the router, without changing the name in the router (in this case 'server')?

As by docs, the behaviour is as expected:
The GetHostEntry method queries a DNS server for the IP addresses and aliases associated with an IP address.
You might want to try this: System.Environment.MachineName
which returns the NETBIOS name of the local machine. See MachineName docs.

Getting a client's IP address

I'm developing an ASP.NET project and I need to determine the client's IP address.
Currently, the following code on our production server
HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"].ToString();
returns an IP address that is in the same subnet as the production server's IP address (i.e., not solving my problem as it's not
the client's IP address).
However, on our test server, that same line of code returns the client's IP address (the desired result). Anyone have an idea why?
I've tried using the above line of code subbing in the following values, all of which return null or an empty string:
"HTTP_X_COMING_FROM"
"HTTP_X_FORWARDED_FOR"
"HTTP_X_FORWARDED"
"HTTP_X_REAL_IP"
"HTTP_VIA"
"HTTP_COMING_FROM"
"HTTP_FORWARDED_FOR"
"HTTP_FORWARDED"
"HTTP_FROM"
"HTTP_PROXY_CONNECTION"
"CLIENT_IP"
"FORWARDED"
As an alternative, I found the following code that does return an array of IP and contains the client's IP address (at index 4):
string strHostName = System.Net.Dns.GetHostName();
IPHostEntry ipEntry = System.Net.Dns.GetHostEntry(strHostName);
IPAddress[] addr = ipEntry.AddressList;
string ip = addr[4] != null ? addr[4].ToString() : "";
While debugging, I noticed that the IPAddress objects in addr have either (A) Address errors if it's an IPv6 address, or (B) ScopeId errors
if it's an IPv4 address. These errors don't seem to be an issue, but I'm not sure if they'll matter once in production.
Is there a better way to get the client's IP address than the way I have here?

Gets the HttpRequestBase object for the current HTTP request.
Request.UserHostAddress
you can get a client's IP address.

You can use this function to get ip address.
private string GetUserIP()
{
string ipList = Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
if (!string.IsNullOrEmpty(ipList))
{
var ips= ipList.Split(',');
return ips[ips.Length - 1];
}
return Request.ServerVariables["REMOTE_ADDR"];
}
NOTE: HTTP_X_FORWARDED_FOR header may have multiple IP's. The correct IP is the last one.

Getting and checking local machine's ip address

I am trying to get IP address on local machine:
private string GetIP()
{
string strHostName = "";
strHostName = System.Net.Dns.GetHostName();
IPHostEntry ipEntry = System.Net.Dns.GetHostEntry(strHostName);
IPAddress[] addr = ipEntry.AddressList;
foreach (IPAddress ipaddr in addr)
{
if (ipaddr.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
return ipaddr.ToString();
}
return "IP error";
}
However I can't find a way to identify which interface is the one i need. For example:
I am lucky that the one i need is second in the list. But if it were in the back i would get IP of a wrong interface. How to check if I am getting IP for local area connection (or in general, the interface responsible for the connection).

You may be able to enumerate the network interfaces directly (rather than just their IPs) and filter then based on their interface type:
var interfaces = NetworkInterface.GetAllNetworkInterfaces()
And then filter it with something like:
interfaces.Where(ni => ni.NetworkInterfaceType != NetworkInterfaceType.Loopback &&
ni.NetworkInterfaceType != NetworkInterfaceType.Tunnel)
It may still return multiple network interfaces but it'll filter out at least some of them that you don't want. I use the above filter to get rid of loopback and virtual machine interfaces.
Then from there you can get the network interface's IP address using the IP properties.
In the spirit of brevity, once you determine which interface is the right one, you can get the IPv4 address (or at least one of them) of the interface using:
iface.GetIPProperties().UnicastAddresses.SingleOrDefault(ua => ua.Address.AddressFamily == AddressFamily.InterNetwork);

There is not method that return one address against the host name
IPAddress[] localIPs = Dns.GetHostAddresses(Dns.GetHostName());
it returns the local machine address for all the registered address in your DNS
So if in your DNS your machine has one name associated to one IP address it will return only that address otherwise it will return the list of addresses associated to that Host Name
you have to "filter" the list to understand what is your local address
Have a look at the below:
How to get the IP address of the server on which my C# application is running on?

Get IPAddress from a hostname

I want to get IP address of a host on my aspx page using C#, I'm using DNS class methods to get these.
It worked fine locally, but when I deployed the solution on IIS7 it returned only the IP address assigned by ISP but I want local IP address of that machine.
Any suggestion?

Here is Example for this.
In this example we can get IP address of our given host name.
string strHostName = "www.microsoft.com";
// Get DNS entry of specified host name
IPAddress[] addresses = Dns.GetHostEntry(strHostName).AddressList;
// The DNS entry may contains more than one IP addresses.
// Iterate them and display each along with the type of address (AddressFamily).
foreach (IPAddress address in addresses)
{
Response.Write(string.Format("{0} = {1} ({2})", strHostName, address, address.AddressFamily));
Response.Write("<br/><br/>");
}

I'm fairly confident that you can not get the local 192.168.C.D address of the local machine like this.
This is because of security and visibility (NAT's etc).
If you are looking to uniquely identify a user. I would look to sessions or cookies.

When looking up the ip address in a public DNS, you will get the officiall IP address communicated outwards. If NAT is used and you want the internal address you have to connect to a DNS server which holds the internal IP addresses.

you can use this method...
public static String GetIP()
{
String ip = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
if(string.IsNullOrEmpty(ip))
{
ip = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
}
return ip;
}

How to get fqdn of ip addresses in c#?

On a machine there might be several IP addresses available. How can I find out all the belonging full qualified domain names (fqdn)?
Update:
I tried the following:
IPHostEntry he = Dns.GetHostEntry(Environment.UserDomainName);
foreach (IPAddress ipAddress in he.AddressList)
{
string x = ipAddress.ToString();
string y = Dns.GetHostEntry(ipAddress.ToString()).HostName;
}
I have a machine with 2 IP addresses, the ping using their fqdn returns the correct IPs. However, the code above always return me the one fqdn of the first IP.
My setup looks as follows:
IP1:
123.123.123.123
Name1
IP2:
456.456.456.456
Name2
Both ping and nslookup returns correct value.
The problem is that both rows
Dns.GetHostEntry("123.123.123.123").HostName;
Dns.GetHostEntry("456.456.456.456").HostName;
returns "Name1" (instead of "Name1" and "Name2").
However, the codes
Dns.GetHostEntry("Name1").HostName;
Dns.GetHostEntry("Name2").HostName;
work correctly.

You resolve each IP address to the netbios name.
Dim hostEntry As System.Net.IPHostEntry = System.Net.Dns.GetHostEntry("192.168.115.54")
Console.WriteLine(hostEntry.HostName)
For example if I resolve my IP i get:
PC-MYNAME.MYDOMAIN.local
Then you can also use ActiveDirectory to enumerate the CurrentForrest (available domains).