Fixed issue #220: Some servers don't like the Range header and respond with errors like 403, 404 or 503. even though the file is perfectly downloadable with a normal request (no Range header).

Author: bezzad

src/Downloader.Test/IntegrationTests/DownloadIntegrationTest.cs

@@ -620,19 +620,22 @@ public async Task TestResumeImmediatelyAfterCanceling()
                 cancellationCompleted.TrySetResult(true);
         };
         Downloader.DownloadProgressChanged += async (_, e) => {
-            try
+            if (canStopDownload && e.ProgressPercentage > 50)
             {
-                await semaphoreSlim.WaitAsync();
-                if (canStopDownload && e.ProgressPercentage > 50)
+                try
                 {
-                    canStopDownload = false;
-                    lastProgressPercentage = e.ProgressPercentage;
-                    await Downloader.CancelTaskAsync();
+                    await semaphoreSlim.WaitAsync();
+                    if (canStopDownload)
+                    {
+                        canStopDownload = false;
+                        lastProgressPercentage = e.ProgressPercentage;
+                        await Downloader.CancelTaskAsync();
+                    }
+                }
+                finally
+                {
+                    semaphoreSlim.Release();
                 }
-            }
-            finally
-            {
-                semaphoreSlim.Release();
             }
         };
 

src/Downloader/Downloader.csproj

@@ -2,7 +2,7 @@
     <PropertyGroup>
         <TargetFrameworks>net8.0;net9.0;net10.0;</TargetFrameworks>
         <LangVersion>latestMajor</LangVersion>
-        <Version>5.1.1</Version>
+        <Version>5.2.0</Version>
         <Title>Downloader</Title>
         <Authors>Behzad Khosravifar</Authors>
         <Company>bezzad</Company>
@@ -11,6 +11,7 @@
         <RepositoryUrl>https://github.com/bezzad/Downloader</RepositoryUrl>
         <PackageTags>download-manager, downloader, download, idm, internet, streaming, download-file, stream-downloader, multipart-download</PackageTags>
         <PackageReleaseNotes>
+            * Fixed issue #220: Some servers don't like the Range header and respond with errors like 403, 404 or 503. even though the file is perfectly downloadable with a normal request (no Range header).
             * Fixed issue #221: resolved file corruption when using ChunkCount on small files by ensuring the final byte of each chunk (especially the last chunk) is written correctly.
         </PackageReleaseNotes>
         <SignAssembly>true</SignAssembly>

src/Downloader/SocketClient.cs

@@ -187,9 +187,12 @@ private async Task FetchResponseHeaders(Request request, bool addRange, Cancella
         }
         catch (HttpRequestException exp)
         {
-            if (addRange && exp.IsRequestedRangeNotSatisfiable())
+            // issue #220: Some servers don't like the Range header and respond with errors like
+            // 403 (Forbidden), 404 (Not Found), or 503 (Service Unavailable)
+            // even though the file is perfectly downloadable with a normal request (no Range header).
+            if (addRange && (exp.IsRequestedRangeNotSatisfiable() || !exp.IsRedirectError()))
             {
-                await FetchResponseHeaders(request, false, cancelToken).ConfigureAwait(false);
+                await FetchResponseHeaders(request, false, cancelToken);
             }
             else if (request.Configuration.AllowAutoRedirect &&
                      exp.IsRedirectError() &&