import java.lang.System;        
import java.net.Socket;        
import java.net.InetAddress;        
import java.net.UnknownHostException;        
import java.io.*;        
 
public class ExChat {        
public static void main(String args[]){        
PortTalk portTalk = new PortTalk(args);        
portTalk.displayDestinationParameters();        
portTalk.displayLocalParameters();        
portTalk.chat();        
portTalk.shutdown();        
}        
}        
class PortTalk {        
Socket connection;        
DataOutputStream outStream;        
BufferedReader inStream;        
public PortTalk(String args[]){        
if(args.length!=2) error("Usage: java PortTalkApp host port");        
String destination = args[0];        
int port = 0;        
try {        
port = Integer.valueOf(args[1]).intValue();        
}catch (NumberFormatException ex){        
error("Invalid port number");        
}        
try{        
connection = new Socket(destination,port);        
}catch (UnknownHostException ex){        
error("Unknown host");        
}        
catch (IOException ex){        
error("IO error creating socket");        
}        
try{        
inStream = new BufferedReader(        
new InputStreamReader(connection.getInputStream()));        
outStream = new DataOutputStream(connection.getOutputStream());        
}catch (IOException ex){        
error("IO error getting streams");        
}        
System.out.println("Connected to "+destination+" at port "+port+".");        
}        
public void displayDestinationParameters(){        
InetAddress destAddress = connection.getInetAddress();        
String name = destAddress.getHostName();        
byte ipAddress[] = destAddress.getAddress();        
int port = connection.getPort();        
displayParameters("Destination ",name,ipAddress,port);        
}        
public void displayLocalParameters(){        
InetAddress localAddress = null;        
try{        
localAddress = InetAddress.getLocalHost();        
}catch (UnknownHostException ex){        
error("Error getting local host information");        
}        
String name = localAddress.getHostName();        
byte ipAddress[] = localAddress.getAddress();        
int port = connection.getLocalPort();        
displayParameters("Local ",name,ipAddress,port);        
}        
public void displayParameters(String s,String name,        
byte ipAddress[],int port){        
System.out.println(s+"host is "+name+".");        
System.out.print(s+"IP address is ");        
for(int i=0;i<ipAddress.length;++i)        
System.out.print((ipAddress[i]+256)*256+".");        
System.out.println();        
System.out.println(s+"port number is "+port+".");        
}        
public void chat(){        
BufferedReader keyboardInput = new BufferedReader(        
new InputStreamReader(System.in));        
boolean finished = false;        
do {        
try{        
System.out.print("Send, receive, or quit (S/R/Q): ");        
System.out.flush();        
String line = keyboardInput.readLine();        
if(line.length()>0){        
line=line.toUpperCase();        
switch (line.charAt(0)){        
case 'S':         
String sendLine = keyboardInput.readLine();        
outStream.writeBytes(sendLine);        
outStream.write(13);        
outStream.write(10);         
outStream.flush();        
break;        
case 'R':        
int inByte;        
System.out.print("***");        
while ((inByte = inStream.read()) != '\n')        
System.out.write(inByte);        
System.out.println();        
break;        
case 'Q':        
finished=true;        
break;        
default:        
break;        
}        
}        
}catch (IOException ex){        
error("Error reading from keyboard or socket");        
}        
} while(!finished);        
}        
public void shutdown(){        
try{        
connection.close();        
}catch (IOException ex){        
error("IO error closing socket");        
}        
}        
public void error(String s){        
System.out.println(s);        
System.exit(1);        
}        
}