gmailService.Users.Messages.Send Error while copying content to a stream.

Error when trying to send a message with an attachment in it. note: total attachment file size is around 15mb

System.Net.Http.HttpRequestException: Error while copying content to a stream. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host
   --- End of inner exception stack trace ---
   at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.ThrowException(SocketError error)
   at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.System.Threading.Tasks.Sources.IValueTaskSource.GetResult(Int16 token)
   at System.Net.Security.SslStreamInternal.<WriteSingleChunk>g__CompleteAsync|36_1[TWriteAdapter](ValueTask writeTask, Byte[] bufferToReturn)
   at System.Net.Security.SslStreamInternal.WriteAsyncChunked[TWriteAdapter](TWriteAdapter writeAdapter, ReadOnlyMemory`1 buffer)
   at System.Net.Security.SslStreamInternal.<WriteAsyncInternal>g__ExitWriteAsync|35_0[TWriteAdapter](ValueTask task)
   at System.
Net.Http.HttpConnection.WriteAsync(ReadOnlyMemory`1 source)
   at System.Net.Http.HttpContent.CopyToAsyncCore(ValueTask copyTask)
   --- End of inner exception stack trace ---
   at Google.Apis.Http.ConfigurableMessageHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) in C:\\Apiary\\2019-08-05.16-52-01\\Src\\Support\\Google.Apis.Core\\Http\\ConfigurableMessageHandler.cs:line 486
   at System.Net.Http.HttpClient.FinishSendAsyncBuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts)
   at Google.Apis.Requests.ClientServiceRequest`1.ExecuteUnparsedAsync(CancellationToken cancellationToken) in C:\\Apiary\\2019-08-05.16-52-01\\Src\\Support\\Google.Apis\\Requests\\ClientServiceRequest.cs:line 231
   at Google.Apis.Requests.ClientServiceRequest`1.Execute() in C:\\Apiary\\2019-08-05.16-52-01\\Src\\Support\\Google.Apis\\Requests\\ClientServiceRequest.cs:line 167

[jskeet]

I’m afraid I don’t know on that front. I suspect it’s just not designed to work like that.

Most of this is really about “the GMail API in general” rather than the .NET client libraries… while I know a bit about some of the APIs, there are far too many for me to be an expert in all of them. I suggest using one of the options listed in the support page for more API-specific information. I’m going to close this issue now as I don’t believe there’s an issue with the .NET client library itself, which is what this specific repository is for. Good luck with your application.

[jskeet]

Right, I suspect that’s the problem - I believe there’s a 25MB limit for that upload field. I suggest:

• Try with a smaller message (e.g. at 24MB) to validate that that really is the issue
• Try uploading the attachments separately as I suggested before