Overview of TCPIP Communications

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Overview of TCP/IP Communications

The whole area of TCP/IP communications is large and complex. This chapter will cover essential TCP/IP topics relevant to Windows CE devices.

TCP/IP provides reliable communication of data. IP (Internet Protocol) defines how data is broken into packets and delivered. TCP (Transmission Control Protocol) provides the mechanism to ensure that the packets are organized into the correct order.

Nearly all communications a programmer is likely to come across are carried out through sockets. A socket on a client device can connect to a socket on a server device, and, once connected, reliable two-way transfer of data can be made. Writing code to communicate through sockets is discussed later in this chapter.

Two important pieces of information must be provided when communicating through sockets:

• IP Address. This address is provided either as the actual address (for example, "192.168.0.2") or as a domain name (for example, "www.microsoft.com"). For the latter, you need to ensure that a Domain Name Server (DNS) is accessible on the network.

• Port Number. Each service type on a server that uses sockets has a unique integer number assigned for each service. This is the port number. Standard protocols (such as HTTP) have standard port numbers (80). You can assign port numbers above 1024 for your own applications.

When communicating using sockets, the programmer defines how the data will be packaged. The data, for example a serialized C++ class or a structure, can be sent as text or binary. Standard protocols (such as HTTP) define how the data will be packaged and specify a protocol to be used between the client and server for communicating requests and data.

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