[c#] How do I get client IP address in ASP.NET CORE?

Can you please let me know how to get client IP address in ASP.NET when using MVC 6. Request.ServerVariables["REMOTE_ADDR"] does not work.

I found that, some of you found that the IP address you get is :::1 or 0.0.0.1

This is the problem because of you try to get IP from your own machine, and the confusion of C# that try to return IPv6.

So, I implement the answer from @Johna (https://stackoverflow.com/a/41335701/812720) and @David (https://stackoverflow.com/a/8597351/812720), Thanks to them!

and here to solution:

1. add Microsoft.AspNetCore.HttpOverrides Package in your References (Dependencies/Packages)

2. add this line in Startup.cs

   public void Configure(IApplicationBuilder app, IHostingEnvironment env)
   {
       // your current code
   
       // start code to add
       // to get ip address
       app.UseForwardedHeaders(new ForwardedHeadersOptions
       {
       ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
       });
       // end code to add
   
   }
   

3. to get IPAddress, use this code in any of your Controller.cs

   IPAddress remoteIpAddress = Request.HttpContext.Connection.RemoteIpAddress;
   string result = "";
   if (remoteIpAddress != null)
   {
       // If we got an IPV6 address, then we need to ask the network for the IPV4 address 
       // This usually only happens when the browser is on the same machine as the server.
       if (remoteIpAddress.AddressFamily == System.Net.Sockets.AddressFamily.InterNetworkV6)
       {
           remoteIpAddress = System.Net.Dns.GetHostEntry(remoteIpAddress).AddressList
   .First(x => x.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork);
       }
       result = remoteIpAddress.ToString();
   }
   

and now you can get IPv4 address from remoteIpAddress or result

Running ASP.NET Core 2.1 behind a Traefik reverse Proxy on Ubuntu, I need to set its gateway IP in KnownProxies after installing the official Microsoft.AspNetCore.HttpOverrides package

        var forwardedOptions = new ForwardedHeadersOptions {
            ForwardedHeaders = ForwardedHeaders.XForwardedFor,
        };
        forwardedOptions.KnownProxies.Add(IPAddress.Parse("192.168.3.1"));
        app.UseForwardedHeaders(forwardedOptions);

According to the documentation, this is required if the reverse proxy is not running on localhost. The docker-compose.yml of Traefik has assigned a static IP address:

networks:
  my-docker-network:
    ipv4_address: 192.168.3.2

Alternatively, it should be enough to make sure a known network is defined here to specify its gateway in .NET Core.

try this.

var host = Dns.GetHostEntry(Dns.GetHostName());
        foreach (var ip in host.AddressList)
        {
            if (ip.AddressFamily == AddressFamily.InterNetwork)
            {
                 ipAddress = ip.ToString();
            }
        }

First, in .Net Core 1.0 Add using Microsoft.AspNetCore.Http.Features; to the controller Then inside the relevant method:

var ip = HttpContext.Features.Get<IHttpConnectionFeature>()?.RemoteIpAddress?.ToString();

I read several other answers which failed to compile because it was using a lowercase httpContext, leading the VS to add using Microsoft.AspNetCore.Http, instead of the appropriate using, or with HttpContext (compiler is also mislead).

var remoteIpAddress = HttpContext.Features.Get<IHttpConnectionFeature>()?.RemoteIpAddress;

You can use the IHttpConnectionFeature for getting this information.

var remoteIpAddress = httpContext.GetFeature<IHttpConnectionFeature>()?.RemoteIpAddress;

In ASP.NET 2.1, In StartUp.cs Add This Services:

services.AddHttpContextAccessor();
services.TryAddSingleton<IActionContextAccessor, ActionContextAccessor>();

and then do 3 step:

1. Define a variable in your MVC controller

   private IHttpContextAccessor _accessor;
   

2. DI into the controller's constructor

   public SomeController(IHttpContextAccessor accessor)
   {
       _accessor = accessor;
   }
   

3. Retrieve the IP Address

   _accessor.HttpContext.Connection.RemoteIpAddress.ToString()
   

This is how it is done.

Running .NET core (3.1.4) on IIS behind a Load balancer did not work with other suggested solutions.

Manually reading the X-Forwarded-For header does.

IPAddress ip;
var headers = Request.Headers.ToList();
if (headers.Exists((kvp) => kvp.Key == "X-Forwarded-For"))
{
    // when running behind a load balancer you can expect this header
    var header = headers.First((kvp) => kvp.Key == "X-Forwarded-For").Value.ToString();
    ip = IPAddress.Parse(header);
}
else
{
    // this will always have a value (running locally in development won't have the header)
    ip = Request.HttpContext.Connection.RemoteIpAddress;
}

In my case, I have DotNet Core 2.2 Web App running on DigitalOcean with docker and nginx as reverse proxy. With this code in Startup.cs I can get the client IP

app.UseForwardedHeaders(new ForwardedHeadersOptions
        {
            ForwardedHeaders = ForwardedHeaders.All,
            RequireHeaderSymmetry = false,
            ForwardLimit = null,
            KnownNetworks = { new IPNetwork(IPAddress.Parse("::ffff:172.17.0.1"), 104) }
        });

::ffff:172.17.0.1 was the ip that I was getting before using

Request.HttpContext.Connection.RemoteIpAddress.ToString();

To get IP address and hostname in .NET Core, put the following code in the controller:

var addlist = Dns.GetHostEntry(Dns.GetHostName());
string GetHostName = addlist.HostName.ToString();
string GetIPV6 = addlist.AddressList[0].ToString();
string GetIPV4 = addlist.AddressList[1].ToString();

This works for me (DotNetCore 2.1)

[HttpGet]
public string Get() 
{
    var remoteIpAddress = HttpContext.Connection.RemoteIpAddress;
    return remoteIpAddress.ToString();
}

In project.json add a dependency to:

"Microsoft.AspNetCore.HttpOverrides": "1.0.0"

In Startup.cs, in the Configure() method add:

  app.UseForwardedHeaders(new ForwardedHeadersOptions
        {
            ForwardedHeaders = ForwardedHeaders.XForwardedFor |
            ForwardedHeaders.XForwardedProto
        });  

And, of course:

using Microsoft.AspNetCore.HttpOverrides;

Then, I could get the ip by using:

Request.HttpContext.Connection.RemoteIpAddress

In my case, when debugging in VS I got always IpV6 localhost, but when deployed on an IIS I got always the remote IP.

Some useful links: How do I get client IP address in ASP.NET CORE? and RemoteIpAddress is always null

The ::1 is maybe because of:

Connections termination at IIS, which then forwards to Kestrel, the v.next web server, so connections to the web server are indeed from localhost. (https://stackoverflow.com/a/35442401/5326387)

Some fallback logic can be added to handle the presence of a Load Balancer.

Also, through inspection, the X-Forwarded-For header happens to be set anyway even without a Load Balancer (possibly because of additional Kestrel layer?):

public string GetRequestIP(bool tryUseXForwardHeader = true)
{
    string ip = null;

    // todo support new "Forwarded" header (2014) https://en.wikipedia.org/wiki/X-Forwarded-For

    // X-Forwarded-For (csv list):  Using the First entry in the list seems to work
    // for 99% of cases however it has been suggested that a better (although tedious)
    // approach might be to read each IP from right to left and use the first public IP.
    // http://stackoverflow.com/a/43554000/538763
    //
    if (tryUseXForwardHeader)
        ip = GetHeaderValueAs<string>("X-Forwarded-For").SplitCsv().FirstOrDefault();

    // RemoteIpAddress is always null in DNX RC1 Update1 (bug).
    if (ip.IsNullOrWhitespace() && _httpContextAccessor.HttpContext?.Connection?.RemoteIpAddress != null)
        ip = _httpContextAccessor.HttpContext.Connection.RemoteIpAddress.ToString();

    if (ip.IsNullOrWhitespace())
        ip = GetHeaderValueAs<string>("REMOTE_ADDR");

    // _httpContextAccessor.HttpContext?.Request?.Host this is the local host.

    if (ip.IsNullOrWhitespace())
        throw new Exception("Unable to determine caller's IP.");

    return ip;
}

public T GetHeaderValueAs<T>(string headerName)
{
    StringValues values;

    if (_httpContextAccessor.HttpContext?.Request?.Headers?.TryGetValue(headerName, out values) ?? false)
    {
        string rawValues = values.ToString();   // writes out as Csv when there are multiple.

        if (!rawValues.IsNullOrWhitespace())
            return (T)Convert.ChangeType(values.ToString(), typeof(T));
    }
    return default(T);
}

public static List<string> SplitCsv(this string csvList, bool nullOrWhitespaceInputReturnsNull = false)
{
    if (string.IsNullOrWhiteSpace(csvList))
        return nullOrWhitespaceInputReturnsNull ? null : new List<string>();

    return csvList
        .TrimEnd(',')
        .Split(',')
        .AsEnumerable<string>()
        .Select(s => s.Trim())
        .ToList();
}

public static bool IsNullOrWhitespace(this string s)
{
    return String.IsNullOrWhiteSpace(s);
}

Assumes _httpContextAccessor was provided through DI.