File Transfer via WCF - wcf

Question

I'm a bit of the newbie to WCF so i would really appreciate if you could answer as detailed as possible :) i have a WCF service library and a WPF application (who is a client). the wanted result is an application that will enable file sharing between the connected clients.I build a really basic WCF service library with one method:
[ServiceContract]
public interface IFileService
{
[OperationContract]
byte[] GetFile(string fullPath);
}
And implemented this method like this:
public class FileService : IFileService
{
public byte[] GetFile(string fullPath)
{
return System.IO.File.ReadAllBytes(fullPath);
}
}
This is the App.config file in the WPF client project:
<system.serviceModel>
<bindings>
<wsHttpBinding>
<binding name="WSHttpBinding_IFileService" closeTimeout="00:01:00"
openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00"
bypassProxyOnLocal="false" transactionFlow="false" hostNameComparisonMode="StrongWildcard"
maxBufferPoolSize="524288" maxReceivedMessageSize="65536"
messageEncoding="Text" textEncoding="utf-8" useDefaultWebProxy="true"
allowCookies="false">
<readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
maxBytesPerRead="4096" maxNameTableCharCount="16384" />
<reliableSession ordered="true" inactivityTimeout="00:10:00"
enabled="false" />
<security mode="Message">
<transport clientCredentialType="Windows" proxyCredentialType="None"
realm="" />
<message clientCredentialType="Windows" negotiateServiceCredential="true"
algorithmSuite="Default" />
</security>
</binding>
</wsHttpBinding>
</bindings>
<client>
<endpoint address="http://localhost:9355/TankusFileTransferService/Service/"
binding="wsHttpBinding" bindingConfiguration="WSHttpBinding_IFileService"
contract="TankusFileService.IFileService" name="WSHttpBinding_IFileService">
<identity>
<userPrincipalName value="GIL-LAPTOP\Gil" />
</identity>
</endpoint>
</client>
</system.serviceModel>
And this is the code from the main window WPF application:
public partial class MainWindow : Window
{
ServiceHost sh;
TankusFileService.FileServiceClient fsc;
public MainWindow()
{
InitializeComponent();
}
private void btn_Connect_Click(object sender, RoutedEventArgs e)
{
Uri uri = new Uri("http://127.0.0.1:1234/");
sh = new ServiceHost(typeof(TankusFileTransferService.FileService), uri);
sh.Open();
lbl_Listener.Content = sh.Description.Endpoints[0].Address.ToString();
}
private void btn_Disconnect_Click(object sender, RoutedEventArgs e)
{
sh.Close();
lbl_Listener.Content = string.Empty;
}
private void btn_GetFile_Click(object sender, RoutedEventArgs e)
{
fsc = new TankusFileService.FileServiceClient();
fsc.Endpoint.Address = new EndpointAddress("http://127.0.0.1:1234/");
fsc.Endpoint.Binding = new BasicHttpBinding();
byte[] bytes = fsc.GetFile(#"D:\mika.txt");
System.IO.File.WriteAllBytes(#"D:\mika_new.txt", bytes);
}
}
After i press the connect button and initialize the ServiceHost object so it can start listening i press the getFile button. when the GetFile() function is called it throws a TimeoutException. Why is this? am i even on the right way for accomplishing my wanted application? Thanks :)

Answer 1

You are likely getting a TimeoutException because it is taking longer to send the file than is allowed by your service.
In your config file for both the server and the client be sure to increase the receiveTimeout and sendTimeout.
You may also bump into size limits as WCF configure the maximum message size, and the file would be considered part of the message. Look at maxBufferPoolSize, maxReceivedMessageSize, and the members below
<readerQuotas
maxDepth="32" maxStringContentLength="8192"
maxArrayLength="16384" maxBytesPerRead="4096"
maxNameTableCharCount="16384" />

Answer 2

A synchronous web service request is not the best way to transfer files about. Even if it works, if you need to scale the endpoint to process concurrent requests you will quickly run in to trouble. By uploading files to service endpoints you are compromising the availability of the endpoint.
A better solution - the WPF app writes the filestream to disk (or a database, ftp server, or queue), then sends a quick one way command message to the server, which then goes and grabs the file.
This is hugely more scalable and will result in far fewer availability-type exceptions.
UPDATE
In my experience, when you upload large files to web service endpoints you can get availability problems, especially if there is any significant concurrency. You can plan for this stuff if you know what your upper bounds are (file sizes, concurrent connections, etc.) and you can formalise this as a service level agreement, but the nature of what you are trying to do (peer-to-peer) is by definition a volatile environment where such planning would be difficult.
However, that said, the fact that your requirement is for P2P means that there ideally shouldn't be a centralised environment to implement the type of store-and-retrieve messaging pattern I am suggesting.
Windows Azure blob storage is an example of how this may be achieved.