Learning Java, 4th Edition

Sockets

Sockets are a low-level programming interface for networked communications. They send streams of data between applications that may or may not be on the same host. Sockets originated in BSD Unix and are, in some programming languages, hairy, complicated things with lots of small parts that can break off and endanger little children. The reason for this is that most socket APIs can be used with almost any kind of underlying network protocol. Since the protocols that transport data across the network can have radically different features, the socket interface can be quite complex.^[37]

The java.net package supports a simplified, object-oriented socket interface that makes network communications considerably easier. If you’ve done network programming using sockets in other languages, you should be pleasantly surprised at how simple things can be when objects encapsulate the gory details. If this is the first time you’ve come across sockets, you’ll find that talking to another application over the network can be as simple as reading a file or getting user input. Most forms of I/O in Java, including most network I/O, use the stream classes described in Chapter 12. Streams provide a unified I/O interface so that reading or writing across the Internet is similar to reading or writing on the local system. In addition to the stream-oriented interfaces, the Java networking APIs can work with the Java NIO buffer-oriented API for highly scalable applications. We’ll see both in this chapter. ...