Simple Chat Server

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smoore smoore is offline Offline
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Simple Chat Server

 
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  #1
Jun 12th, 2009
Okay so I found some code online to create a simple chat server and I was trying to teach myself with it. I have a few questions though.

First off here is the code:

ChatServer.java
Java Syntax (Toggle Plain Text) 
  1. import java.io.IOException;
  2. import java.net.InetAddress;
  3. import java.net.Socket;
  4. import java.net.ServerSocket;
  5. import java.net.UnknownHostException;
  6. import java.util.Scanner;
  7.  
  8.  
  9. public class ChatServer 
  10. {
  11. 	// set default port value here
  12. 	public static final int DEFAULT_PORT = 9800;
  13. 	//user can change port with optional command line argument
  14.  
  15. 	public static void main (String[] args) throws UnknownHostException
  16. 	{
  17. 		// variables
  18. 		int port = DEFAULT_PORT;
  19. 		ServerSocket serverSocket = null;
  20. 		Socket socket = null;
  21. 		Scanner keyboard = new Scanner(System.in);
  22.  
  23. 		System.out.print("Enter a port (enter to use default): ");
  24. 		String port_s = keyboard.nextLine();
  25.  
  26. 		try
  27. 		{
  28. 				// change the port number from the default one
  29. 				if(!port_s.equals(""))
  30. 					port = Integer.parseInt(port_s);
  31.  
  32. 				InetAddress thisIp = InetAddress.getLocalHost();
  33. 				System.out.println("\nServer info: \n");
  34. 			    System.out.println("IP: "+thisIp.getHostAddress());
  35. 			    System.out.println("Port: " + port);
  36.  
  37. 		}
  38. 		catch(NumberFormatException nfe)// if the user entered something other than a number
  39. 		{
  40. 			System.err.println("Enter a valid number for port!");
  41. 			System.exit(0);
  42. 		}
  43.  
  44. 		try
  45. 		{
  46. 			serverSocket = new ServerSocket(port);
  47.  
  48. 			while(true)
  49. 			{
  50. 				socket = serverSocket.accept();
  51. 				ChatHandler handler = new ChatHandler(socket);
  52. 				handler.start();
  53. 			}
  54. 		}
  55. 		catch(IOException ioe)
  56. 		{
  57. 			ioe.printStackTrace();
  58. 		}
  59. 		finally
  60. 		{
  61. 			try{serverSocket.close();}
  62. 			catch(IOException ioe){ioe.printStackTrace();}
  63. 		}
  64. 	}
  65. }

ChatHandler.java:
Java Syntax (Toggle Plain Text) 
  1. import java.io.IOException;
  2. import java.net.InetAddress;
  3. import java.net.Socket;
  4. import java.net.ServerSocket;
  5. import java.net.UnknownHostException;
  6. import java.util.Scanner;
  7.  
  8.  
  9. public class ChatServer 
  10. {
  11. 	// set default port value here
  12. 	public static final int DEFAULT_PORT = 9800;
  13. 	//user can change port with optional command line argument
  14.  
  15. 	public static void main (String[] args) throws UnknownHostException
  16. 	{
  17. 		// variables
  18. 		int port = DEFAULT_PORT;
  19. 		ServerSocket serverSocket = null;
  20. 		Socket socket = null;
  21. 		Scanner keyboard = new Scanner(System.in);
  22.  
  23. 		System.out.print("Enter a port (enter to use default): ");
  24. 		String port_s = keyboard.nextLine();
  25.  
  26. 		try
  27. 		{
  28. 				// change the port number from the default one
  29. 				if(!port_s.equals(""))
  30. 					port = Integer.parseInt(port_s);
  31.  
  32. 				InetAddress thisIp = InetAddress.getLocalHost();
  33. 				System.out.println("\nServer info: \n");
  34. 			    System.out.println("IP: "+thisIp.getHostAddress());
  35. 			    System.out.println("Port: " + port);
  36.  
  37. 		}
  38. 		catch(NumberFormatException nfe)// if the user entered something other than a number
  39. 		{
  40. 			System.err.println("Enter a valid number for port!");
  41. 			System.exit(0);
  42. 		}
  43.  
  44. 		try
  45. 		{
  46. 			serverSocket = new ServerSocket(port);
  47.  
  48. 			while(true)
  49. 			{
  50. 				socket = serverSocket.accept();
  51. 				ChatHandler handler = new ChatHandler(socket);
  52. 				handler.start();
  53. 			}
  54. 		}
  55. 		catch(IOException ioe)
  56. 		{
  57. 			ioe.printStackTrace();
  58. 		}
  59. 		finally
  60. 		{
  61. 			try{serverSocket.close();}
  62. 			catch(IOException ioe){ioe.printStackTrace();}
  63. 		}
  64. 	}
  65. }

My Questions:
1) How would I print something once a person enters the chat (telnets domain [port])
2) I would like to use this to ask each person as they enter for a username they would like to use
3) Is that ip address printing correctly for other people? I think it is merely printing my local ipaddress that is associated with the router (not too familiar with ip addresses and stuff like that)
4) More general question: What is the difference between a vector and ArrayList?

Thanks a lot guys.
Last edited by smoore; Jun 12th, 2009 at 11:10 pm.
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JamesCherrill JamesCherrill is offline Offline
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Re: Simple Chat Server

 
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  #2
Jun 13th, 2009
4. Only real difference is that Vector is synchronized, ie it's automatically safe to use in a multi-threaded app. ArrayList isn't.
ps: You may not think you have a multi-threaded app, but if you use Swing, then you do.
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stewie griffin stewie griffin is offline Offline
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Re: Simple Chat Server

 
0
  #3
Jun 13th, 2009
Well, I don’t see the ChatHandler class , but it should have a run method , in the run method (assuming you work with sockets) you shall ask for username, password exec,and use InputStreamReader and / or PrintWriter,
For exemple:
Java Syntax (Toggle Plain Text) 
  1. requestOut = new PrintWriter(socket.getOutputStream(), true);
and than
Java Syntax (Toggle Plain Text) 
  1. requestOut.println(userInput);

the server / client must be coordinated

in every ChatHandler add some variable that will contain the nickname
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Re: Simple Chat Server

 
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  #4
Jun 16th, 2009
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Originally Posted by stewie griffin View Post
Well, I don’t see the ChatHandler class ....
Here it is again but it is also in the first post:

Java Syntax (Toggle Plain Text) 
  1. import java.io.IOException;
  2. import java.net.InetAddress;
  3. import java.net.Socket;
  4. import java.net.ServerSocket;
  5. import java.net.UnknownHostException;
  6. import java.util.Scanner;
  7.  
  8.  
  9. public class ChatServer 
  10. {
  11. 	// set default port value here
  12. 	public static final int DEFAULT_PORT = 9800;
  13. 	//user can change port with optional command line argument
  14.  
  15. 	public static void main (String[] args) throws UnknownHostException
  16. 	{
  17. 		// variables
  18. 		int port = DEFAULT_PORT;
  19. 		ServerSocket serverSocket = null;
  20. 		Socket socket = null;
  21. 		Scanner keyboard = new Scanner(System.in);
  22.  
  23. 		System.out.print("Enter a port (enter to use default): ");
  24. 		String port_s = keyboard.nextLine();
  25.  
  26. 		try
  27. 		{
  28. 				// change the port number from the default one
  29. 				if(!port_s.equals(""))
  30. 					port = Integer.parseInt(port_s);
  31.  
  32. 				InetAddress thisIp = InetAddress.getLocalHost();
  33. 				System.out.println("\nServer info: \n");
  34. 			    System.out.println("IP: "+thisIp.getHostAddress());
  35. 			    System.out.println("Port: " + port);
  36.  
  37. 		}
  38. 		catch(NumberFormatException nfe)// if the user entered something other than a number
  39. 		{
  40. 			System.err.println("Enter a valid number for port!");
  41. 			System.exit(0);
  42. 		}
  43.  
  44. 		try
  45. 		{
  46. 			serverSocket = new ServerSocket(port);
  47.  
  48. 			while(true)
  49. 			{
  50. 				socket = serverSocket.accept();
  51. 				ChatHandler handler = new ChatHandler(socket);
  52. 				handler.start();
  53. 			}
  54. 		}
  55. 		catch(IOException ioe)
  56. 		{
  57. 			ioe.printStackTrace();
  58. 		}
  59. 		finally
  60. 		{
  61. 			try{serverSocket.close();}
  62. 			catch(IOException ioe){ioe.printStackTrace();}
  63. 		}
  64. 	}
  65. }
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