// introduction to client sockets in Java, by Narendra Singhal and
// Norman Matloff; paired with Svr.java

// usage:  java Clnt remotehost command
// where command is w or ps

// sends the command to remotehost, which runs it there and sends us
// back the output of the command

// note:  at the bottom level, there are still the standard system
// calls, e.g. socket(), connect(), bind(), etc.; the difference is that
// in Java they are made by the underlying JVM, rather than by the
// programmer him/herself

import java.lang.*;
import java.io.*;
import java.net.*;

public class Clnt 

{
   private static final int Port = 3000;

   private static Socket Sock = null;       

   public static void main (String Args[])
	
   {  try {

         try {
            // class Socket is for TCP (use class DatagramSocket for
            // UDP); note that the "connect" action is included in the
            // operations done in invoking the constructor
            Sock = new Socket(Args[0],Port);  
         }
         // Socket() throws UnknownHostException, IOException
         catch (UnknownHostException E)  {
            System.out.println(E+":  check remote host address");
	    System.exit(1);
         }
         catch(IOException E)  {
            System.out.println(E+":  some other socket/connect problem");
            System.exit(1);
         }

         InputStream Input = Sock.getInputStream();
         OutputStream Output = Sock.getOutputStream();
         // getInputStream() and getOutputStream() return pointers to
         // the types InputStream and OutputStream, respectively;
         // we'll just use these as is, without chaining to more
         // efficient buffered I/O classes

         // send the command to the remotehost
         for (int I = 0; I < Args[1].length(); I++)
            Output.write(Args[1].charAt(I)); 

         // read the response from the remote host, and print it out
	 // on the screen; we'll build up lines byte-by-byte, though it
         // could be done more compactly if we used more advanced
         // machinery, such as BufferedReader.readLine()
         int ByteFromServer;
         String Line = "";
         while (true)  {
            ByteFromServer = Input.read();
            if (ByteFromServer == '\n')  {
               if (Line.equals("end")) System.exit(1);
               System.out.println(Line); 
               Line = "";
            }
            else Line = Line + (char) ByteFromServer;
         }
      }
      // catch exceptions which may arise during Input.read()
      catch(IOException E)  {
         System.out.println(E+":  broken connection with server");
         System.exit(1);
      }
   }
}