- Everything You Need To Know about TCP/IP but Failed to Learn in Kindergarten
- A Client Socket in Java
- Sending Email by Java
- A Server Socket in Java
- HTTP and Web Browsing: Retrieving HTTP Pages
- How to Make an Applet Write a File on the Server
- A Multithreaded HTTP Server
- A Mapped I/O HTTP Server
- Further Reading
- Exercises
- Some Light Relief—Using Java to Stuff an Online Poll
This chapter is from the book
This chapter is from the book
This chapter is from the book
A Mapped I/O HTTP Server
The final section of this chapter presents the code to use the new mapped I/O facility in a socket server. Sun distributes a sample mapped I/O socket application with JDK 1.4 beta. However, their sample application does not work on Windows 98. It hangs in the accept() statement.
I reported the bug to Sun and hope it will be fixed in the final release. It may not be: after all, mapped I/O is a server feature, and Windows 9x is not a server operating system. Anyway, as a refresher, an example of channel I/O on files would be this program that duplicates a file:
import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.net.*;
class Files {
void copyThruChannel(String fname) throws Exception {
File f = new File(fname);
FileInputStream fin = new FileInputStream(f);
int len = (int) f.length();
FileChannel fc = fin.getChannel();
System.out.println("allocating buff");
ByteBuffer myBB = ByteBuffer.allocate(len);
int bytesRead = fc.read(myBB);
myBB.flip();
System.out.println("getting fout channel");
FileOutputStream fos = new FileOutputStream(fname+".copy.txt");
FileChannel fco = fos.getChannel();
int bytesWritten = fco.write(myBB);
fco.close();
}
public static void main(String a[]) throws Exception {
Files client = new Files();
client.copyThruChannel(a[0]);
}
}
In a similar way, the code to update our HTTP server, so that it uses channel I/O, looks like this:
import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.net.*;
class OneConnection_D extends OneConnection_C {
OneConnection_D(Socket sock) throws Exception {
super(sock);
}
void sendThruChannel(String fname) throws Exception {
File f = new File(fname);
FileInputStream fin = new FileInputStream(f);
int len = (int) f.length();
FileChannel fc = fin.getChannel();
System.out.println("allocating buff");
ByteBuffer myBB = ByteBuffer.allocate(len);
int bytesRead = fc.read(myBB);
myBB.flip();
System.out.println("getting sock channel");
SocketChannel sc = sock.getChannel();
int bytesWritten = sc.write(myBB);
sc.close();
}
}
public class HTTPServer4 {
public static void main(String a[]) throws Exception {
final int httpd = 80;
ServerSocketChannel ssc = ServerSocketChannel.open();
InetSocketAddress isa
= new InetSocketAddress(InetAddress.getLocalHost(), httpd);
ssc.socket().bind(isa);
System.out.println("have opened port 80 locally!");
System.out.println("waiting for accept");
Socket sock = ssc.accept();
System.out.println("client has made socket connection");
OneConnection_D client = new OneConnection_D(sock);
String filename = client.getRequest();
client.sendThruChannel(filename);
}
}
Note: This version is not multithreaded to keep the code focused on the issue of interest. The main routine shows how you have to open a server socket channel, then bind it to the port of interest. From here it is easy to use mapped I/O.