import java.io.*;
import java.net.*;
/* ***************************************************************
                                                 Bert G. Wachsmuth
                                                      June 3, 1996
   LineClient object

   Connects to a socket on a machine through tcpip and offers send 
   and receive lines through that socket to a line server. This object 
   offers the following public methods:

   public LineClient(String _Host, int _Port) - the constructor
      PRE:  _Host is a string indicating the Internet address of a 
             Host, _Port is the port number to use for a connection
      POST: Instantiates a LineClient

   public String Open()
     PRE:  LineClient must be instantiated
     POST: Opens connection to port on host and sets up input and 
           output streams. Blocks server for any other connection.
           Returns a string containing identifier sent by server.

   public String Close()
     PRE:  LineClient is instantiated and connection has been opened.
     POST: Closes streams and socket and frees server for next connection.

   public String ReceiveLine()
     PRE:  LineClient is instantiated and connection has been opened.
     POST: Returns response from server as String. 
   
   public void SendLine(String s) or
   public void SendLine(int i)
     PRE:  LineClient is instantiated and connection has been opened.
     POST: Sends a String s through the socket to the server.

   NOTE: The server *must* send one identifier line immediately on 
         connect (returned in open() method).
   *************************************************************** */
public class LineClient
{
   String Host;
   int    Port;

   Socket theSocket;
   PrintStream outStream;
   DataInputStream inStream;
/* *************************************************************** */
   public LineClient(String _Host, int _Port)
   {
      Host = _Host;
      Port = _Port;
   }
/* *************************************************************** */
   public String Open()
   {
      try 
      {
         theSocket = new Socket(Host, Port);
         outStream = new PrintStream(theSocket.getOutputStream());
         inStream  = new DataInputStream(theSocket.getInputStream());
         return ReceiveLine();
      }
      catch (UnknownHostException e) 
      {
         System.err.println("Unknown host exception:" + e);
         return "ERROR: Unknown host.";
      } 
      catch (Exception e) 
      {
         System.err.println("Unknown exception:  " + e);
         return "ERROR: Unknown exception.";
      }
   }
/* *************************************************************** */
   public String Close()
   {
      try
      {
         outStream.close();
         inStream.close();
         theSocket.close();
         return "Connection closed.";
      }
      catch(Exception e) 
      {
         System.err.println("Could not clean up. Exception:  " + e);
         return "ERROR: connection broke before closing.";
      }
   }
/* *************************************************************** */
   public String ReceiveLine()
   {
      try
      {
         return inStream.readLine();
      }
      catch(Exception e)
      {
         System.err.println("Unknown IO exception: " + e);
         Close();
         return null;
      }
   }
/* *************************************************************** */
   public void SendLine(String s)
   {
      try
      {
         outStream.println(s);
         outStream.flush();
      }
      catch(Exception e)
      {
          System.err.println("Unknown IO exception: " + e);
          Close();
      }
   }
/* *************************************************************** */
   public void SendLine(int i)
   {
      try
      {
         outStream.println(i);
         outStream.flush();
      }
      catch(Exception e)
      {
          System.err.println("Unknown IO exception: " + e);
          Close();
      }
   }
/* **************************************************** */
}