Network Communications

Windows CE supports a network stack with a number of options. Network communications can take place over a variety of hardware, including infrared, serial, Ethernet, and wireless links. Although the network stack is accessible only through the Winsock interface, Windows CE also provides several high-level APIs that use Winsock internally, and handle the details of setting up and managing socket connections:

• The WinINET API provides support for Internet browsing protocols, including FTP and HTTP 1.0. It also provides access to three Internet security protocols, Secure Sockets Layer (SSL) 2.0, Secure Sockets Layer 3.0, and Private Communication Technology (PCT) 1.0.
• The WNet API provides access to remote file systems through a Common Internet File System (CIFS) redirector. Currently, operating system connections are supported only for Microsoft® Windows® 95 and Microsoft® Windows NT®. The redirector supports UNC names, such as //serverXX/shareXX, but not drive letters.
• ICMP requests, commonly referred to as pings, are used to determine whether or not a host is available.

The Winsock interface provides direct access to the network stack. Windows CE supports a subset of Winsock 1.1, as well as the three Internet security protocols mentioned earlier. For infrared communication, Windows CE supports the IrSock extension of Winsock, which enables socket-based infrared communication using the industry-standard IrDA protocols.

Windows CE supports a RAS client at the same level in the network stack as Winsock, but this client serves a different purpose. RAS is a multi-protocol router used to connect remote devices. The Windows CE RAS client is identical to the Win32 RAS, except it supports only one point-to-point connection at a time.

The TCP/IP suite, developed for the Internet, is arguably the most flexible and widely implemented network protocol. It is supported by a wide variety of systems and forms the core of the Windows CE network stack. Many Windows CE-based mobile devices have wireless communication capabilities. However, conventional TCP/IP stacks may work poorly with wireless technology because they were intended to function efficiently on wired networks. The Windows CE TCP/IP stack is designed to be configured for wireless networking.

At the base of the network stack, Windows CE supports data-link layers for serial-link networks and local area networks (LANs). Many Windows CE-based devices connect to a network using a serial communication link, such as a modem. To support serial-link networking, Windows CE implements the widely used serial line Internet (SLIP) and Point-to-Point Protocol (PPP). Three protocols are available for authentication in serial-link communication: Password Authentication Protocol (PAP), Challenge Handshake Authentication Protocol (CHAP), and Microsoft CHAP.

To support connections to LANs, Windows CE implements NDIS 4.0, but supports only Ethernet miniport drivers. Windows CE does not support wide area networks (WANs). For more information on NDIS support, see the documentation for the Windows CE DDK.