Distributed Systems – Elliott Solution

These running programs are provided as a guide. TYPE THEM IN and get them running on your own
machine. Along the way you will likely make some mistakes in transcription that have to be repaired.
Once you have them running, you can play with them by making modifications.
The byte-compiled .class files from these programs are also available in the course directories, so that
you can use, e.g., the existing client to test your own server, or the existing server to test your own client.
I do not require you to type in, and get running, or turn in, the standalone InetAddresser program.
However this is a first step in getting this program running, and, once you have typed it in and gotten it
running, then much of it will be useful in the InetServer and InetClient programs via copy/paste.
I recommend that you first make sure that Java and TCP/IP are running correctly on your machine by
loading and running the InetAddresser, and the InetServer and InetClient byte-compiled .class files. These
should work "out of the box." You may find that you have to turn off, or play with, your firewall. If you are
concerned about security you can unplug your local home network from the internet, but leave the
connections between your local home machines active.
Then, if you are advanced programmer you can write your own java multi-threaded server and client.
Otherwise TYPE IN THE PROGRAMS and get them running. This is an excellent way to learn. If you are
clever you can probably figure a way to scan the text from the .pdf file, but this will not help you to learn
the material and I strongly do NOT recommend it.
Use your own variable names, and alter the logic as you see fit, as long as it runs, and has comments.
Once you have the client and server running, CHANGE THE PORT number to something higher and
announce the port when the server starts up. Run your client and server on different machines if you
have more than one available. Run several clients at once with the single server.
Tip: start small and get something running first, then gradually add functionality, and complexity. But,
always keep your program running.
These programs are explicitly given without many comments. This is intentional because I want YOU to
figure out exactly what is going on, and write your own comments, which is an important part of your
grade.
Good luck. Have fun.
-CE/** File is: InetServer.java, Version 1.8 (small)
A multithreaded server for InetClient. Elliott, after Hughes, Shoffner, Winslow
This will not run unless TCP/IP is loaded on your machine.
----------------------------------------------------------------------*/
import java.io.*; // Get the Input Output libraries
import java.net.*; // Get the Java networking libraries
class Worker extends Thread {
Socket sock;
Worker (Socket s) {sock = s;}
// Class definition
// Class member, socket, local to Worker.
// Constructor, assign arg s to local sock
public void run(){
// Get I/O streams in/out from the socket:
PrintStream out = null;
BufferedReader in = null;
try {
in = new BufferedReader
(new InputStreamReader(sock.getInputStream()));
out = new PrintStream(sock.getOutputStream());
// Note that this branch might not execute when expected:
try {
String name;
name = in.readLine ();
System.out.println("Looking up " + name);
printRemoteAddress(name, out);
} catch (IOException x) {
System.out.println("Server read error");
x.printStackTrace ();
}
sock.close(); // close this connection, but not the server;
} catch (IOException ioe) {System.out.println(ioe);}
}
static void printRemoteAddress (String name, PrintStream out) {
try {
out.println("Looking up " + name + "...");
InetAddress machine = InetAddress.getByName (name);
out.println("Host name : " + machine.getHostName ()); // To client...
out.println("Host IP : " + toText (machine.getAddress ()));
} catch(UnknownHostException ex) {
out.println ("Failed in atempt to look up " + name);
}
}
// Not interesting to us:
static String toText (byte ip[]) { /* Make portable for 128 bit format */
StringBuffer result = new StringBuffer ();
for (int i = 0; i < ip.length; ++ i) {
if (i > 0) result.append (".");
result.append (0xff & ip[i]);
}
return result.toString ();
}
}public class InetServer {
public static void main(String a[]) throws IOException {
int q_len = 6; /* Not intersting. Number of requests for OpSys to queue */
int port = 1565;
Socket sock;
ServerSocket servsock = new ServerSocket(port, q_len);
System.out.println
("Clark Elliott's Inet server 1.8 starting up, listening at port 1565.\n");
while (true) {
sock = servsock.accept(); // wait for the next client connection
new Worker(sock).start(); // Spawn worker to handle it
}
}
}