DTPT Overview (Windows Embedded CE 6.0)


ActiveSync uses the Desktop Pass-through (DTPT) technology to perform synchronization. DTPT is a technology that enables a Windows Embedded CE-based device to transparently access external networks such as the Internet, through the desktop computer to which it is connected. DTPT replaces the previous method of connecting using an emulated serial port over USB.

There is full connectivity between the desktop and the device. However, there is limited connectivity between the desktop running ActiveSync and the external host. Only outgoing TCP/IPv4 packets are routed through the DTPT Server to the external host.

The following illustration shows the DTPT components.


The DTPT architecture is comprised of the following components:

DTPT Client

The DTPT Client service runs on the Windows Embedded CE-based device. This component is responsible for addressing and forwarding connect and name service provider requests to the desktop. For more information about layered service provider, see Layered Protocols and Provider Chains. DTPT Client modules are as follows:

  • DTPT_Srv.dll - Performs addressing for the Windows Embedded CE-based client.
  • DTPT_LSP.dll - A layered service provider that forwards connect requests to the desktop for processing.
  • DTPT_NSP.dll - A name service provider that forwards name service provider requests to the desktop for processing.
DTPT Server

The DTPT Server service runs on the desktop to which the Windows Embedded CE-based device is connected and is integrated with ActiveSync. This component is used by the device as a proxy server to connect to external networks to which the desktop is connected. It also processes NSP requests sent by the DTPT Client.

After the device connects to the desktop, the DTPT Client and the DTPT Server attempt to discover each other.

The DTPT Client (DTPT_Srv.dll) performs addressing by detecting the presence of a DTPT compatible network interface. After an appropriate interface is detected, the DTPT Client assigns an IPv4 address for the device from the Auto IP range of addresses and then sends the address to the desktop by using the DHCP protocol.

If an application running on the device attempts to change the IP address of the device, the DTPT functionality may fail.

After the addressing is performed, a connection is established and the DTPT Server listens on a predetermined port for messages sent by the DTPT Client. Based on the type of message received, the DTPT Server functions as a proxy server or a name service provider.

The purpose of DTPT is to enable a Windows Embedded CE-based device to connect to and communicate with remote hosts on the network to which the desktop is connected. The DTPT Server functions as a proxy forwarding data between the device and the remote host. DTPT Client (DTPT_LSP.dll) intercepts the proxy calls and sends the request to the desktop for processing.

DTPT also supports name service provider service. When a Winsock application running on the device make a request for name resolution, the DTPT Client (DTPT_NSP.dll) intercepts this call and forwards the call to the DTPT Server for processing. The DTPT Server receives the NSP message and retrieves the requested service information and returns it to the DTPT Client.

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