Error uploading image (in bytes) to a HTTP file server

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C#

I am trying to upload an image (in bytes) from a HTTP server. I am encountering an error "An existing connection was forcibly closed by the remote host" when using the code below. DownloadData and UploadFile methods are working. Please help.

string image = @"C:\.....\helloX2.pdf";<br />
byte[] ImageData = System.IO.File.ReadAllBytes(image);<br />
Uri _uri = new Uri(@"http://XXX.XXX.XX.X:8080/MyHTTPFileServer/helloX2.pdf");<br />
WebClient client = new WebClient();<br />
client.Credentials = CredentialCache.DefaultCredentials;<br />
byte[] responseArray = client.UploadData(_uri, "POST",ImageData);<br />
string x = Encoding.ASCII.GetString(responseArray);<br />
client.Dispose();

What I have tried:

DownloadData and UploadFile methods are working.