ag in attached code . Why the NetworkStream.Read hang(block) internet connection?

Hi All
I have to major the HTTP traffic via proxy, When I try to upload any image or any files  it goes to hang or block. As my observation the StreamReader make it block and it is bind with NetworkStream.
   while (totalBytesRead < contentLen && (bytesRead = clientStreamReader.ReadBlock(postBuffer, 0, contentLen)) > 0)
                    {
                        totalBytesRead += bytesRead;
                        sw.Write(postBuffer, 0, bytesRead);
                        Console.Write(postBuffer, 0, bytesRead);
                    }
Can you help me why it block or Hang?

private  void ProxyProcessing(TcpClient client)
        {
         //   client.ReceiveTimeout = 150000;
          //  client.SendTimeout = 150000;
            Stream mainStream = client.GetStream();
            Stream outStream = mainStream; 
            SslStream sslStream = null;
            StreamReader clientStreamReader = new StreamReader(mainStream);
           
            MemoryStream cacheStream = null;            
      
            try
            {
                //read the first line HTTP command
                String httpCmd = clientStreamReader.ReadLine();
                if (String.IsNullOrEmpty(httpCmd))
                {
                    clientStreamReader.Close();
                    mainStream.Close();
                    return;
                }
                //break up the line into three components
                String[] splitBuffer = httpCmd.Split(spaceSplit, 3);

                String method = splitBuffer[0];
                String remoteUri = splitBuffer[1];
                Version version = new Version(1, 1);

                HttpWebRequest webReq;
                HttpWebResponse response = null;
                if (splitBuffer[0].ToUpper() == "CONNECT")
                {
                    clientStreamReader.Close();
                    mainStream.Close();
                    return;
                }

                //construct the web request that we are going to issue on behalf of the client.
                webReq = (HttpWebRequest)HttpWebRequest.Create(remoteUri);
                webReq.Method = method;
                webReq.ProtocolVersion = version;

                //read the request headers from the client and copy them to our request
                int contentLen = ReadRequestHeaders(clientStreamReader, webReq);
                
                webReq.Proxy = null;
                webReq.KeepAlive = false;
                webReq.AllowAutoRedirect = false;
                webReq.AutomaticDecompression = DecompressionMethods.None;
        
              
                if (method.ToUpper() == "POST")
                {
                    char[] postBuffer = new char[contentLen];
                    int bytesRead;
                    int totalBytesRead = 0;
                    StreamWriter sw = new StreamWriter(webReq.GetRequestStream());

                    while (totalBytesRead < contentLen && (bytesRead = clientStreamReader.ReadBlock(postBuffer, 0, contentLen)) > 0)
                    {                       
                        totalBytesRead += bytesRead;
                        sw.Write(postBuffer, 0, bytesRead);                        
                        Console.Write(postBuffer, 0, bytesRead);
                    }    
                    sw.Close();
                }
                    
                   webReq.Timeout = 15000;

                    try
                    {
                        response = (HttpWebResponse)webReq.GetResponse();
                    }
                    catch (WebException webEx)
                    {
                        response = webEx.Response as HttpWebResponse;
                    }
                    if (response != null)
                    {
                        List<Tuple<String,String>> responseHeaders = ProcessResponse(response);
                        StreamWriter myResponseWriter = new StreamWriter(outStream);
                        Stream responseStream = response.GetResponseStream();
                        try
                        {
                            //send the response status and response headers
                            WriteResponseStatus(response.StatusCode,response.StatusDescription, myResponseWriter);
                            WriteResponseHeaders(myResponseWriter, responseHeaders);

                            Byte[] buffer;
                            if (response.ContentLength > 0)
                                buffer = new Byte[response.ContentLength];
                            else
                                buffer = new Byte[BUFFER_SIZE];

                            int bytesRead;

                            while ((bytesRead = responseStream.Read(buffer, 0, buffer.Length)) > 0)
                            {
                                if (cacheStream != null)
                                    cacheStream.Write(buffer, 0, bytesRead);
                                outStream.Write(buffer, 0, bytesRead);                             
                            }

                            responseStream.Close();                         

                            outStream.Flush();
                         
                        }
                        catch (Exception ex)
                        {
                            Console.WriteLine(ex.Message);
                        }
                        finally
                        {
                            responseStream.Close();
                            response.Close();
                            myResponseWriter.Close();
                        }
                    }                
              
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            finally
            {
                clientStreamReader.Close();
                mainStream.Close();
                if (sslStream != null)
                    sslStream.Close();
                outStream.Close();              
            }
        }