basic FTP between a unix and linux machine

[anirudh takkallapally]

hi ,
i have a unix machine , form this machine i have to send some data to a linux machine and invoke a process in the linux machine, this process will generate a GIF image , i have to capture that GIF image and get the image back to the unix machine.....
can any body please tell me how to connect to the linux machine , invoke a process and get the image back... , the unix and linux machine are in the netwok..
please help....
thanks...

[Joe Ess]

Not quite "basic" FTP. You want the Linux machine to offer a service on some port that the Unix machine can send data to and receive the GIF from. Assuming both machines have a Java VM, you could accomplish this by fleshing out the following server code and running it on the Linux box:

 
import java.io.*;
import java.net.*;
/**
DataServer is an example of how to create a service on a port.  It does nothing 
useful except echo the client's data back to the client.  It is only suitable
for very simple tasks since it is not multithreaded and has no security. 
*/
public class DataServer{
   
   public static final int PORT = 12345;      
   
   public static void main(String args[]){
       
      ServerSocket ss = null;              
       
      // attempt to open a port for our service 
      try{
         ss = new ServerSocket(PORT);
      } catch (Exception e){         
         e.printStackTrace();
         System.exit(0);
      }
      
      while(true){
         try{            
            System.out.println("Waiting on client");
         // wait for client to connect   
            Socket in = ss.accept();
            System.out.println("Client connected");
         // read client data               
            ObjectInputStream ois = new ObjectInputStream(in.getInputStream());
            System.out.println("Reading client data");
            Object o = ois.readObject(); 
                        
            System.out.println("Server received data: "+o.toString());
         // use Runtime.exec() to call external process
         
         // locate and read in GIF file
         
         // send data back to client
            ObjectOutputStream oos = new ObjectOutputStream(in.getOutputStream());
            oos.writeObject(o);      
            oos.flush();
            
         // free our socket resources   
            ois.close();
            oos.close();
            in.close();
         } catch (Exception e){
            e.printStackTrace();
         }
      }
   }
}
 

Then running a client on the Unix box that looks something like this:

 
import java.io.*;
import java.net.*;
/**
DataClient is an example of how to contact a server and get a reply
*/
public class DataClient{
      
   static String dataStr = "This is a test string 123456789012345678901234567890123456789012345678901234567890";
   
   public static void main(String args[]){
      Socket s = null;
      try{
      // contact the server   
         s = new Socket("localhost", DataServer.PORT);         
         System.out.println("Got Connection");
      // one would read in initial data here
      
      // send data to server
         ObjectOutputStream oos = new ObjectOutputStream(s.getOutputStream());         
         oos.writeObject(dataStr);
         System.out.println("Wrote Data");
         oos.flush();
                                                      
         System.out.println("Waiting on server");
      // get reply from server   
         ObjectInputStream ois = new ObjectInputStream(s.getInputStream());         
         Object o = ois.readObject();
         
      // free our socket's resources      
         oos.close();   
         ois.close();
         System.out.println("Client received data: "+o.toString());
      // one would process server's reply here   
      } catch(Exception e){
         e.printStackTrace();
      } finally {
         if (s != null){
            try{s.close();}
            catch(Exception e){}
         }
      }
   }
}