Why IHttpClientFactory Will Save Your .NET App (and Your TCP Ports!)

As .NET developers, we’ve all done this:

var client = new HttpClient();

It’s easy, it works… until your app starts failing unexpectedly due to port exhaustion.
In this article, I’ll explain:

• Why creating multiple HttpClientinstances is dangerous
• How IHttpClientFactorysolves the problem
• How to structure your code using Clean Architecture

❌ The Problem with new HttpClient()

Bad practice: creating HttpClient for every request

public async Task<string> GetWeatherAsync()
{
    using var client = new HttpClient();
    var response = await client.GetAsync("https://api.weather.com/forecast");
    return await response.Content.ReadAsStringAsync();
}

Why is this bad?
Each new HttpClient() opens a fresh TCP connection. When used frequently (e.g., in loops or heavy API calls), this leads to port exhaustion, causing your HTTP requests to fail.

The Right Approach:IHttpClientFactory

.NET introduced IHttpClientFactoryto manage reusable and efficient HttpClientinstances.

Step 1: Define a Service Interface (Clean Architecture)

public interface IWeatherService
{
    Task<string> GetForecastAsync();
}

Step 2: Implement the Service

public class WeatherService : IWeatherService
{
    private readonly HttpClient _httpClient;

    public WeatherService(HttpClient httpClient)
    {
        _httpClient = httpClient;
    }

    public async Task<string> GetForecastAsync()
    {
        var response = await _httpClient.GetAsync("/forecast");
        response.EnsureSuccessStatusCode();
        return await response.Content.ReadAsStringAsync();
    }
}

Step 3: Configure HttpClient in Program.cs

builder.Services.AddHttpClient<IWeatherService, WeatherService>(client =>
{
    client.BaseAddress = new Uri("https://api.weather.com");
    client.DefaultRequestHeaders.Add("Accept", "application/json");
});

With IHttpClientFactory, .NET reuses connections under the hood, improves performance, and avoids port exhaustion.

What About You?

• Have you ever experienced port exhaustion in production?
• Do you prefer Named Clients or Typed Clients with IHttpClientFactory?
• Let me know in the comments – I’d love to hear your experience!

About Me
I’m a C#/.NET & Angular fullstack developer, passionate about building robust SaaS applications and clean, testable architectures
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