Unable to call external api from webaplication hosted in docker

Question

My webapplication is running on docker and trying to call external api which is hosted on IIS and I am not able to access external api. Throwing below error : but when my webapplication is running on local iis then able to connect api and get the response. Please help me on this.

InnerException {System.Net.Http.HttpRequestException: No such host is known ---> System.Net.Sockets.SocketException: No such host is known at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, enter image description hereCancellationToken cancellationToken) --- End of inner exception stack trace --- at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken) at System.Threading.Tasks.ValueTask1.get_Result() at System.Net.Http.HttpConnectionPool.CreateConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken) at System.Threading.Tasks.ValueTask1.get_Result() at System.Net.Http.HttpConnectionPool.WaitForCreatedConnectionAsync(ValueTask1 creationTask) at System.Threading.Tasks.ValueTask1.get_Result() at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken) at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) at System.Net.Http.HttpClient.FinishSendAsyncUnbuffered(Task1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts) at System.Net.Http.HttpClient.GetStringAsyncCore(Task1 getTask)} System.Exception {System.Net.Http.HttpRequestException}

Answer 1

I think the problem is Docker DNS server. You can try to use a real DNS server such as 8.8.8.8

If you are using Docker on Windows, you can try to update DNS setting 8.8.8.8

If you are using Ubuntu, you can try this setting:

# /etc/docker/daemon.json
{
    "dns": ["8.8.8.8"]
}

Answer 2

For macOs and Windows, you could try host.docker.internal.

Replace the localhost with host.docker.internal.

        public async Task<IActionResult> About()
    {
        //ViewData["Message"] = "Your application description page.";
        HttpClient client = new HttpClient();
        //var result = await client.GetStringAsync(@"http://localhost/IISWindows/home/test");
        var result = await client.GetStringAsync(@"http://host.docker.internal/IISWindows/home/test");
        ViewData["Message"] = result;
        return View();
    }

If you are running docker in linux, you could try build a new container to redirect the request to host, for more information refer docker-host.