Programming C#, Third Edition

Network I/O

Writing to a remote object on the Internet is not very different from writing to a file on your local machine. You might want to do this if your program needs to store its data to a file on a machine on your network, or if you are creating a program that displays information on a monitor connected to another computer on your network.

Network I/O is based on the use of streams created with sockets. Sockets are very useful for client/server applications, peer to peer (P2P), and when making remote procedure calls.

A socket is an object that represents an endpoint for communication between processes communicating across a network. Sockets can work with various protocols, including UDP and TCP/IP. In this section, we create a TCP/IP connection between a server and a client. TCP/IP is a connection-based protocol for network communication. Connection-based means that with TCP/IP, once a connection is made, the two processes can talk with one another as if they were connected by a direct phone line.

Tip

Although TCP/IP is designed to talk across a network, you can simulate network communication by running the two processes on the same machine.

It is possible for more than one application on a given computer to be talking to various clients all at the same time (e.g., you might be running a web server, an FTP server, and a program that provides calculation support). Therefore, each application must have a unique ID so that the client can indicate which application it is looking ...