package Worksheet3;

//
// EchoServer.java
// Acts as an echo server.
// Client must connect on the correct port.
// Server closes the connection on receiving 'END'.
// But keeps running for more client connections.
//
// Give the port number as a command line argument:
// e.g. java EchoServer [4567]
//
import java.io.*;
import java.net.*;

public class EchoServer {

      public final static int DEFAULT_PORT = 3456;
      public final static int qLen = 3; // number of clients that can q

      public void EchoServer() {
      }

      public static void main(String[] args) throws IOException {
            ServerSocket listenSocket = null;
            OutputStreamWriter osw = null;
            InputStreamReader isr = null;
            BufferedReader br = null;
            int portNum = DEFAULT_PORT;
            int clientNo = 0; // count clients serviced

            if (args.length != 0) {
                  try {
                        portNum = Integer.parseInt(args[ 0]);
// put some test here to allow for port number not in range
                  } catch (NumberFormatException nfE) {
                        System.err.println("Illegal port number: " + args[ 0]);
                        System.err.println("\tUsing the default: " + DEFAULT_PORT);
                  }
            }
            try {
                  listenSocket = new ServerSocket(portNum, qLen);
            } catch (BindException e) {
                  System.err.println("Could not bind to port: " + portNum);
                  System.err.println("\tIs it already in use?");
                  System.err.println("\tIs it a reserved port number?");
                  System.exit(1);
            }
            while (true) { // loop forever accepting clients
                  Socket clientSocket = null;
// try changing for isr rather than br
                  String request = null;
                  try {
                        clientSocket = listenSocket.accept(); // actual comms socket!
                        ++clientNo; // count clients serviced
                        osw = new OutputStreamWriter(clientSocket.getOutputStream());
// the above line might need , "US-ASCII"); or // "UTF-8"?
                        System.out.println("Connection from: "
                                + clientSocket.getInetAddress());
                        isr = new InputStreamReader(clientSocket.getInputStream());
// the above line might need , "US-ASCII"); or // "UTF-8"?
                        br = new BufferedReader(isr);
                        do {
// try changing for isr rather than br
                              request = br.readLine();
                              System.out.println("\tFrom client " + clientNo + ": " + request);
// What happens if we don't send '\r\n' or only one of them?
                              osw.write("Hello from " + InetAddress.getLocalHost() + " to Client no:" + clientNo + "\r\n");

                              osw.flush(); // make sure msg got sent from the buffer!
                        } while (!request.equals("END"));
                        System.out.println("Client " + clientNo + " closed connection");
                        osw.close();
                        isr.close();
                        br.close();
                        clientSocket.close();
                  } // end try{} accepting a client connection
                  catch (IOException ioE) {
                        System.err.println("Connection error, maybe the client died!");
                  } finally { // to trap any other errors!!
                        try {
                              if (clientSocket != null) {
                                    clientSocket.close();
                              }
                        } catch (IOException ioE) {
                        }
                  } // end of finally
            } // while forever waiting for a client connection
      } // main
} // class EchoServer