Java Network Programming: Developing Networked Applications
Java Network Programming exposes the power and sophistication of this library. In , in the first chapter of the first edition of this book, I wrote extensively about the sort of dynamic, distributed network applications I thought Java would make possible. One of the most exciting parts of writing subsequent editions has been seeing virtually all of the applications I postulated come to pass.
Java in general and network programming in Java in particular has moved well beyond the hype stage and into the realm of real, working applications. Efforts are well under way to subvert the existing infrastructure of C-based network clients and servers with pure Java replacements.
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- Socket class.
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Clients for newer protocols like Gnutella and Freenet are preferentially written in Java. This book has come a long way, too. The third edition has one completely new chapter to describe the most significant development in network programming since readers and writers were introduced in Java 1. It removes one of the last barriers to using Java for network servers. There've been lots of other small changes and updates throughout the java. IPv6 has become a reality, and is now covered extensively.
Java Socket Programming
Many other methods have been added to existing classes in the last two releases of Java, and these are discussed in the relevant chapters. I've also rewritten large parts of the book to reflect changing fashions in Java programming in general and network programming in particular. Applets and CGI programs are emphasized much less. Each of these applications use the client-server paradigm, which we discussed earlier. Java sockets have input streams and output streams built in, which makes programming rather pleasant. Four applications are presented in order of increasing complexity: A trivial date server and client , illustrating simple one-way communication.
The server sends data to the client only. A capitalize server and client , illustrating two-way communication , and server-side threads to more efficiently handle multiple connections simultaneously. A two-player tic tac toe game , illustrating a server that needs to keep track of the state of a game , and inform each client of it, so they can each update their own displays.
A multi-user chat application , in which a server must broadcast messages to all of its clients. These applications communicate insecurely. None of these applications even try to secure communication.
ID HT Network Programming
All data is sent between hosts completely in the clear. The goal at this point is to illustrate the most basic applications and how they use transport-level services. In real life, use a secure sockets layer. A Trivial Sequential Server This is perhaps the simplest possible server. It listens on port When a client connects, the server sends the current datetime to the client. The connection socket is created in a try-with-resources block so it is automatically closed at the end of the block. Only after serving the datetime and closing the connection will the server go back to waiting for the next client.
IOException; import java. PrintWriter; import java. ServerSocket; import java. Socket; import java. Woah nc is amazing! Scanner; import java. Exits after printing the response. The previous example was pretty trivial: it did not read any data from the client, and worse, it served only one client at a time. This next server receives lines of text from a client and sends back the lines uppercased. It efficiently handles multiple clients at once : When a client connects, the server spawns a thread, dedicated to just that client, to read, uppercase, and reply. The server can listen for and serve other clients at the same time, so we have true concurrency.
Now for a pretty simple command line client: CapitalizeClient. InputStreamReader; import java.
- Socket class.
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It can be used interactively:. Here is the server for multiple two-player games. It listens for two clients to connect, and spawns a thread for each: the first is Player X and the second is Player O. The client and server send simple string messages back and forth to each other; messages correspond to the Tic Tac Toe protocol, which I made up for this example. Arrays; import java.