This chapter covers
What is Netty?
Some History
Introducing Netty
Asynchrony and Events
About this Book
WHAT IS NETTY?
Netty is a client/server framework that harnesses the power of Java's advanced networking
while hiding its complexity behind an easy-to use API. Netty provides performance and
scalability, leaving you free to focus on what really interests you - your unique application!
In this first chapter we'll explain how Netty provides value by giving some background on
the problems of high-concurrency networking. Then we'll introduce the basic concepts and
building blocks that make up the Netty toolkit and that we'll be studying in depth in the rest of
the book.
SOME HISTORY
If you had started out in the early days of networking you would have spent a lot of time
learning the intricacies of sockets, addressing and so forth, coding on the C socket libraries,
and dealing with their quirks on different operating systems.
The first versions of Java (1995-2002) introduced just enough object-oriented sugar-
coating to hide some of the intricacies, but implementing a complex client-server protocol still
required a lot of boilerplate code (and a fair amount of peeking under the hood to get it right).
Those early Java APIs (java.net) supported only the so-called "blocking" functions
provided by the native socket libraries. An unadorned example of server code using these calls
is shown in 0.
Listing 1.1 Blocking I/O Example
ServerSocket serverSocket = new ServerSocket(portNumber); //1
Socket clientSocket = serverSocket.accept(); //2
BufferedReader in = new BufferedReader( //3
new InputStreamReader(clientSocket.getInputStream()));
PrintWriter out =
new PrintWriter(clientSocket.getOutputStream(), true);
String request, response;
while ((request = in.readLine()) != null) { //4
if (Done.equals(request) ( //5
break;
}
response = processRequest(request); //6
out.println(response); //7
} //8
1. A ServerSocket is created to listen for connection requests on a specified port.
2. The accept() call blocks until a connection is established. It returns a new Socket which will be used
for the conversation between the client and the server.
©Manning Publications Co. We welcome reader comments about anything in the manuscript - other than typos and
other simple mistakes. These will be cleaned up during production of the book by copyeditors and proofreaders.
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