Downloading mod thumbnail using C# HttpClient

[Rikitav]

I programming a small browser on C# to view and download mods using the internal Mod Portal API. Everything works gorgeous and the lists of mods are loaded, but when it comes to the assets, problems began. I use the most ordinary HttpClient for requests and when I try to request Thumbnail (let it be https://assets-mod.factorio.com/assets/ ... .thumb.png), the request is faulting with the exception "this host is unknown. (Assets-mod.Factorio.com:443)", although everything in the regular browser is calmly opening.

[danbopes]

"Host is unknown" indicates a DNS resolution failure. Ensure the link is correct (And no whitespace characters) and wherever the code is running ensure has proper Internet access.

[Rikitav]

"Host is unknown" indicates a DNS resolution failure. Ensure the link is correct (And no whitespace characters) and wherever the code is running ensure has proper Internet access.

I checked everything, the link is correct, there is Internet access, I even managed to download thumbnail ONCE, but after that it also gives an error. Maybe I need to indicate additional information to the request or are there any restrictions on access to this domain?

[danbopes]

Can you share some of the code (Like a minimal snippet), and I can try to help further.

[Rseding91]

I don't have an answer to your issue (it should just work) - the internal game logic simply downloads the thumbnails and caches them in memory for the lifetime of the application.

However, on your project - there's no issue with what you're doing in general - but do be careful to not hand out your authentication token for people to use as that's against the TOS (bypassing the need to own the game) and will likely end with your account being permanently disabled.

[eugenekay]

I use the most ordinary HttpClient for requests and when I try to request Thumbnail (let it be https://assets-mod.factorio.com/assets/ ... .thumb.png), the request is faulting with the exception "this host is unknown. (Assets-mod.Factorio.com:443)", although everything in the regular browser is calmly opening.

What is the Actual C# error message, and your calling code? This sounds like a DNS resolution failure; not yet getting to sending the HTTP request. Do you actually have “Assets-mod.Factorio.com” capitalized in your Code? All DNS labels should be normalized to lowercase before doing a Lookup; I don’t remember exactly how the various .Net SDK versions handle this case…

[danbopes]

I just wrote this dirt simple script to show that downloading assets works perfectly fine:

Code: Select all

using System.Text.RegularExpressions;

var client = new HttpClient();

var html = await client.GetStringAsync("https://mods.factorio.com/");

var matches = Regex.Matches(html, @"""(https://assets-mod\.factorio\.com/[^\""]+)\""");

foreach (Match match in matches)
{
    var url = match.Groups[1].Value;
    Console.WriteLine($"Downloading thumb: {url}");

    var fileName = Path.GetFileName(url);


    var stream = await client.GetStreamAsync(url);

    using var fs = File.OpenWrite(fileName);

    await stream.CopyToAsync(fs);
}

Downloaded all 20 images, and dumped them in the folder. You're doing something funky with the URL, or your DNS resolution is finicky. This is 100% on your end.

[Rikitav]

Do you actually have “Assets-mod.Factorio.com” capitalized in your Code? All DNS labels should be normalized to lowercase before doing a Lookup;

About this... my english is very bad, so i used translator to write this message, its his fault, my request address is in lowercase.

[Rikitav]

Can you share some of the code (Like a minimal snippet), and I can try to help further.

Code: Select all

// "BitmapSource" is WPF's class
// "ModPageShortInfo" is class i use for deserialize mods 'short' info request

private const string AssetsUrl = "https://assets-mod.factorio.com";

public async Task<BitmapSource?> DownloadThumbnail(ModPageShortInfo modPage, CancellationToken cancellationToken = default)
{
    if (string.IsNullOrEmpty(modPage.Thumbnail))
	return null;
	
    try
    {
        await ThumbnailDownloadSemaphore.WaitAsync(cancellationToken);
        string thumbnailUrl = AssetsUrl + modPage.Thumbnail; // <--- CORRECT URL! CHECKED MANY TIMES!
        Debug.WriteLine("Requesting thumbnail : " + thumbnailUrl);

        using (HttpResponseMessage response = await httpClient.GetAsync(thumbnailUrl)) // This is where i getting an exception
        {
            response.EnsureSuccessStatusCode();
            using (Stream contentStream = await response.Content.ReadAsStreamAsync())
            {
                BitmapImage bitmapImage = new BitmapImage();
                
                bitmapImage.BeginInit();
                bitmapImage.StreamSource = new MemoryStream();
                contentStream.CopyTo(bitmapImage.StreamSource);
                bitmapImage.EndInit();

                modPage.DownloadedThumbnail = bitmapImage;
            }
        }
    }
    catch (Exception ex)
    {
        Debug.WriteLine("Failed to load the image :", ex.Message);
    }

    ThumbnailDownloadSemaphore.Release();
    return modPage.DownloadedThumbnail;
}

[Rikitav]

I just wrote this dirt simple script to show that downloading assets works perfectly fine:

In fact, at some point the code began to work and the pictures were downloading, even a long amount of time and after many application restarts. This morning when I checked, the method stopped working again.

[Rikitav]

What is the Actual C# error message

Code: Select all

System.Net.Http.HttpRequestException: "This host is unknown. (assets-mod.factorio.com:443)"

Just this

[Rikitav]

However, on your project - there's no issue with what you're doing in general - but do be careful to not hand out your authentication token for people to use as that's against the TOS (bypassing the need to own the game) and will likely end with your account being permanently disabled.

May they forgive me Wube, but I myself do not have a Factorio license, I play through a pirated version. The game in my region costs a lot of money, I just can't afford it at this age

[danbopes]

I just wrote this dirt simple script to show that downloading assets works perfectly fine:

In fact, at some point the code began to work and the pictures were downloading, even a long amount of time and after many application restarts. This morning when I checked, the method stopped working again.

You have a DNS issue, either in your router, or your ISP. I suggest using hardcoded public IP's for DNS resolution, like using google's DNS resolvers @ 8.8.8.8 and 8.8.4.4.

Could also be a VPN issue if you're using a VPN to access stuff.

[Rikitav]

You have a DNS issue, either in your router, or your ISP. I suggest using hardcoded public IP's for DNS resolution, like using google's DNS resolvers @ 8.8.8.8 and 8.8.4.4.

Could also be a VPN issue if you're using a VPN to access stuff.

alternate DNS resolver worked like a charm! TYSM!