//: c16:NameCollector.java
// From Thinking in Java, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
// Extracts email names from datagrams and stores
// them inside a file, using Java 1.02.
import java.net.*;
import java.io.*;
import java.util.*;

public class NameCollector {
  final static int COLLECTOR_PORT = 8080;
  final static int BUFFER_SIZE = 1000;
  byte[] buf = new byte[BUFFER_SIZE];
  DatagramPacket dp = 
    new DatagramPacket(buf, buf.length);
  // Can listen & send on the same socket:
  DatagramSocket socket;
  Process listmgr;
  PrintStream nameList;
  DataInputStream addResult;
  public NameCollector() {
    try {
      listmgr =
        Runtime.getRuntime().exec("listmgr.exe");
      nameList = new PrintStream(
        new BufferedOutputStream(
          listmgr.getOutputStream()));
      addResult = new DataInputStream(
        new BufferedInputStream(
          listmgr.getInputStream()));

    } catch(IOException e) {
      System.err.println(
        "Cannot start listmgr.exe");
      System.exit(1);
    }
    try {
      socket =
        new DatagramSocket(COLLECTOR_PORT);
      System.out.println(
        "NameCollector Server started");
      while(true) {
        // Block until a datagram appears:
        socket.receive(dp);
        String rcvd = new String(dp.getData(),
            0, 0, dp.getLength());
        // Send to listmgr.exe standard input:
        nameList.println(rcvd.trim());
        nameList.flush();
        byte[] resultBuf = new byte[BUFFER_SIZE];
        int byteCount = 
          addResult.read(resultBuf);
        if(byteCount != -1) {
          String result = 
            new String(resultBuf, 0).trim();
          // Extract the address and port from 
          // the received datagram to find out 
          // where to send the reply:
          InetAddress senderAddress =
            dp.getAddress();
          int senderPort = dp.getPort();
          byte[] echoBuf = new byte[BUFFER_SIZE];
          result.getBytes(
            0, byteCount, echoBuf, 0);
          DatagramPacket echo =
            new DatagramPacket(
              echoBuf, echoBuf.length,
              senderAddress, senderPort);
          socket.send(echo);
        }
        else
          System.out.println(
            "Unexpected lack of result from " +
            "listmgr.exe");
      }
    } catch(SocketException e) {
      System.err.println("Can't open socket");
      System.exit(1);
    } catch(IOException e) {
      System.err.println("Communication error");
      e.printStackTrace();
    }
  }
  public static void main(String[] args) {
    new NameCollector();
  }
} ///:~