// 儅儖僠僉儍僗僩斉僠儍僢僩僾儘僌儔儉Chat.java
// 偙偺僾儘僌儔儉偼,儅儖僠僉儍僗僩傪巊偭偰僠儍僢僩婡擻傪採嫙偟傑偡
// 巊偄曽java Chat [億乕僩斣崋]

// 儔僀僽儔儕偺棙梡
import java.net.*;
import java.io.*;

// Chat僋儔僗
// Chat僋儔僗偼,庴怣僗儗僢僪傪嶌惉丒幚峴偟,憲怣傪扴摉偟傑偡
public class Chat {
	final byte TTL = 1 ;//摨堦僙僌儊儞僩撪晹偺傒摓払壜擻偲偟傑偡
	final String MULTICASTADDRESS = ("224.0.0.1") ;
				// 儅儖僠僉儍僗僩傾僪儗僗224.0.0.1偼,
				// 儖乕僞傪挻偊側偄応崌偺傾僪儗僗偱偡
	int port = 6000 ;
				// 僠儍僢僩梡偺億乕僩斣崋,巜掕偑側偗傟偽6000 斣偲偟傑偡
	byte[] buff = new byte[1024] ;//憲怣梡僶僢僼傽
	String myname ="" ;// 棙梡幰柤
	int nameLength = 0 ;//棙梡幰柤偺挿偝
	MulticastSocket soc = null ; // 儅儖僠僉儍僗僩僜働僢僩
	InetAddress chatgroup = null ; //僠儍僢僩梡傾僪儗僗

	// 僐儞僗僩儔僋僞棙梡幰柤側偳傪愝掕偟傑偡
	public Chat(int portno){
	port = portno ; //億乕僩斣崋偺愝掕
	BufferedReader lineread
	  = new BufferedReader(new InputStreamReader(System.in)) ;
	System.out.println("偍柤慜傪偳偆偧") ;
	try{
		myname = lineread.readLine() ;
	}catch(Exception e){
		e.printStackTrace() ;
		System.exit(1) ;
	}
	System.out.println("傛偆偙偦" + myname + "偝傫.") ;
	myname = myname + ">" ;
	nameLength = (myname.getBytes()).length ;
	for(int i = 0;i < nameLength;++i)
		buff[i] = (myname.getBytes())[i] ;
	}

	// makeMulticastSocket儊僜僢僪
	//MULTICASTADDRESS偵懳偟偰儅儖僠僉儍僗僩僜働僢僩傪嶌惉偟傑偡
	public void makeMulticastSocket()
	{
		try{
			chatgroup
				= InetAddress.getByName(MULTICASTADDRESS) ;
			soc = new MulticastSocket(port) ;
			soc.joinGroup(chatgroup) ;
		}
		catch(Exception e){
			e.printStackTrace() ;
			System.exit(1);
		}
	}

	// startLintener儊僜僢僪
	// 僗儗僢僪梡僋儔僗ListenPacket偺僆僽僕僃僋僩傪惗惉偟,婲摦偟傑偡
	public void startListener()
	{
		try{
			ListenPacket lisner =
				new ListenPacket(soc);
			Thread lisner_thread = new Thread(lisner);
			lisner_thread.start();//庴怣僗儗僢僪偺奐巒
		}
		catch(Exception e){
			e.printStackTrace() ;
			System.exit(1);
		}
	}

	// sendMsgs儊僜僢僪
	// 儅儖僠僉儍僗僩僷働僢僩偺憲怣傪扴摉偟傑偡
	public void sendMsgs()
	{
		try{
			// 憲怣儖乕僾
			while(true){
				int n = System.in.read(
						buff,nameLength ,1024 - nameLength ) ;
				if(n > 0){
					DatagramPacket dp
						= new DatagramPacket(
						buff,n + nameLength,chatgroup,port) ;
					soc.send(dp) ;
				}
				else break ;// 儖乕僾廔椆
			}
		}
		catch(Exception e){
			e.printStackTrace() ;
			System.exit(1);
		}
	}

	// quitGroup儊僜僢僪
	// 愙懕傪廔椆偟傑偡
	public void quitGroup()
	{
		try{
			// 愙懕偺廔椆
			System.out.println("愙懕廔椆") ;
			soc.leaveGroup(chatgroup) ;
			System.exit(0) ;
		}
		catch(Exception e){
			e.printStackTrace() ;
			System.exit(1);
		}
	}

	// main儊僜僢僪
	public static void main(String[] arg){
		Chat c = null ;
		int portno = 6000 ;
		if(arg.length >= 1) portno = Integer.parseInt(arg[0]) ;
		c = new Chat(portno) ;
		c.makeMulticastSocket() ;
		c.startListener() ;
		c.sendMsgs() ;
		c.quitGroup() ;
	}
}

// ListenPacket僋儔僗
// 儅儖僠僉儍僗僩僷働僢僩傪庴怣偟傑偡
class ListenPacket implements Runnable {
	MulticastSocket s = null;
	// 僐儞僗僩儔僋僞儅儖僠僉儍僗僩僗儗僢僪傪庴偗庢傝傑偡
	public ListenPacket(MulticastSocket soc){
		s = soc;
	}
	// 張棟偺杮懱
	public void run(){
		byte[] buff = new byte[1024] ;
		try{
			while(true){
				DatagramPacket recv
					= new DatagramPacket(buff,buff.length) ;
				s.receive(recv) ;
				if(recv.getLength() > 0){
					System.out.write(buff,0,recv.getLength()) ;
				}
			}
		}catch(Exception e){
			e.printStackTrace() ;
			System.exit(1) ;
		}
	}
}