WCF maxBytesPerRead限制为4096

我在蒸汽模式下使用基本WCF web服务从服务器下载文件。

我已将服务器端的绑定指定为

     <basicHttpBinding>
        <binding name="DBUpdateServiceBinding" closeTimeout="23:59:59"
           openTimeout="23:59:59" receiveTimeout="23:59:59" sendTimeout="23:59:59"
           maxReceivedMessageSize="10067108864" messageEncoding="Mtom"
           transferMode="Streamed">
           <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
              maxBytesPerRead="8192" maxNameTableCharCount="16384" />
        </binding>
     </basicHttpBinding>

我的客户端绑定xml看起来像

  <bindings>
     <basicHttpBinding>
        <binding name="ws" closeTimeout="23:59:59" openTimeout="23:59:59"
           receiveTimeout="23:59:59" sendTimeout="23:59:59" maxReceivedMessageSize="10067108864"
           messageEncoding="Mtom" transferMode="Streamed">
           <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
              maxBytesPerRead="8192" maxNameTableCharCount="16384" />
           <security>
              <transport realm="" />
           </security>
        </binding>
     </basicHttpBinding>
  </bindings>

我正在尝试使用下载文件

   byte[] buffer = new byte[32768];
   while (true)
   {
      int read = serverStream.Read(buffer, 0, buffer.Length);
      if (read <= 0)
         break;
      fs.Write(buffer, 0, read);
   }

尽管我已经指定了maxBytesPerRead=“8192”,但我在一个调用中可以读取的最大字节数只有4096。