Sockets and relaying messages

Question

sirlink99 56 Practically a Master Poster

12 Years Ago

I am just learning how to use sockets, and I have managed to get my server to send a message to my socket, but when I try to send a message from my socket to my server I get an error. Here are my codes

Server:

package BasicNIO;

import java.io.*;
import java.net.*;
import java.nio.*;

public class ServerSockets {

	ServerSocket servSock;
	Socket sock;
	
	public ServerSockets (){
		
		// creates a new server socket at port 5555
		try {
			servSock = new ServerSocket (5555);
			 System.out.println("Server Started: " + servSock);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		// creates a socket that uses the server socket
		
		 try {
			sock = servSock.accept();
			System.out.println("Client Connected: " + sock);
			
			PrintStream ps = new PrintStream (sock.getOutputStream ());
			ps.println ("Server: Hello"); // sends message
			ps.close(); // closes print stream
			
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		 System.out.println(" Connection from :  " + sock.getInetAddress());
		 
		  try {
			DataInputStream is = new DataInputStream(sock.getInputStream());
			System.out.println(is.readLine());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		try {
			sock.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} // closes socket connection
	}
	
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		ServerSockets ss = new ServerSockets ();
		
		
	}

}

Client:

package BasicNIO;

import java.io.*;
import java.net.*;
import java.nio.*;

public class Sockets {

	Socket sock;
	
	public Sockets (){
		InetAddress ip;
		try {
			ip = InetAddress.getByName
			 ("192.168.0.100");
			sock = new Socket (ip,5555);
		} catch (UnknownHostException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		try {
			PrintStream ps = new PrintStream(sock.getOutputStream());
			ps.println ("Client: Hi Server");
			DataInputStream is = new DataInputStream(sock.getInputStream());
			String message = is.readLine();
			System.out.println (message);
			ps.close();
			sock.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public static void main (String [] args){
		Sockets s = new Sockets ();
		
		
		
	}
	
}

Thanks for any help.

java

2 Contributors
17 Replies
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10 Hours Discussion Span
Latest Post 12 Years Ago Latest Post by NormR1

All 17 Replies

NormR1 563 Posting Sage

12 Years Ago

I try to send a message from my socket to my server I get an error

Can you post the full text of the error message?

NormR1 563 Posting Sage

12 Years Ago

Line 2 says that the socket is closed? Is that right?

NormR1 563 Posting Sage

12 Years Ago

I prefer to test client/server code in the same JVM. That way the debug output shows the order of events in both sides.

Who closes the socket connection first?

NormR1 563 Posting Sage

12 Years Ago

Make then internal classes and add a main:

public class ClientServerSockets {

	public static void main(String[] args) {
            Thread t = new Thread(new Runnable() {
                 public void run() {
		    ServerSockets ss = new ServerSockets ();
                 }
            });
            t.start();
 
            Sockets s = new Sockets ();
        } //end main()

Edited 12 Years Ago by NormR1 because: n/a

NormR1 563 Posting Sage

12 Years Ago

Now its time to add lots of print statement to show when everything is happening.
Enter a method.
Open a connection
close anything
Be sure to add a prefix to the messages so you know who printed it. For example:

System.out.println("S - Client Connected: " + sock);
System.out.println ("C msg=" + message);
System.out.println("S read=" + is.readLine());

Edited 12 Years Ago by NormR1 because: n/a

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sirlink99 56 Practically a Master Poster · Answer 1 · 2011-09-20T03:44:54+00:00

output for ServerSockets

Server Started: ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=5555]
java.net.SocketException: Socket is closed
	at java.net.Socket.getInputStream(Unknown Source)
	at BasicNIO.ServerSockets.<init>(ServerSockets.java:39)
	at BasicNIO.ServerSockets.main(ServerSockets.java:56)
Client Connected: Socket[addr=/192.168.0.100,port=57223,localport=5555]
 Connection from :  /192.168.0.100

output for Sockets

Server: Hello

sirlink99 56 Practically a Master Poster · Answer 2 · 2011-09-20T03:50:35+00:00

It shouldn't be closed. I close the socket after I try to get the message sent by the client.

line 39 & 40 I get try to get the message

line 46 I close the socket

sirlink99 56 Practically a Master Poster · Answer 3 · 2011-09-20T03:58:33+00:00

I don't know which one closes the socket first. I think when the the server tries to read the message the client either didn't send the message (and therefore I cannot read it), or the Client didn't connect at the time when I try to read it.

The second option is valid, because it displays the error, and then it prints out that the client connected.

Also how do I test two programs in the same vm?

sirlink99 56 Practically a Master Poster · Answer 4 · 2011-09-20T04:10:20+00:00

This is the output that I get

Server Started: ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=5555]
java.net.SocketException: Socket is closed
	at java.net.Socket.getInputStream(Unknown Source)
	at BasicNIO.ServerSockets.<init>(ServerSockets.java:38)
	at SocketExamples.testTogether$1.run(testTogether.java:17)
	at java.lang.Thread.run(Unknown Source)
Client Connected: Socket[addr=/192.168.0.100,port=58134,localport=5555]
 Connection from :  /192.168.0.100
Server: Hello

from this code

package BasicNIO;

import java.awt.event.*;


public class testTogether {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		 Thread t = new Thread(new Runnable() {
             public void run() {
            	 ServerSockets ss = new ServerSockets ();
             }
        });
		t.start();
		Sockets s = new Sockets();
		
	}

}

which runs my previous codes

sirlink99 56 Practically a Master Poster · Answer 5 · 2011-09-20T04:22:23+00:00

This is the output I get when I add in a bunch of printlns

S - Server Started: ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=5555]
S - Waiting for a Connection
C - Setting up adress
C - Creating socket
C - Socket Created
C - Creating PrintStream
C - Created! Sending Message
C - Message Sent
C - Creating DataInputStream
C - Created. Attempting to read message
java.net.SocketException: Socket is closed
	at java.net.Socket.getInputStream(Unknown Source)
	at BasicNIO.ServerSockets.<init>(ServerSockets.java:44)
	at BasicNIO.testTogether$1.run(testTogether.java:15)
	at java.lang.Thread.run(Unknown Source)
S - Connection Accepted
Client Connected: Socket[addr=/192.168.0.100,port=58320,localport=5555]
S - Sending message
S - Message Sent
S - PrintStream Closed
 Connection from :  /192.168.0.100
S - Entering reading try-catch statement
S - Creating DataInputStream
C - Message read, and assigned to a variable 'message'
C - Printing message
Server: Hello
C - Message Printed. Closing DataInputStream
C - Closed. Closing PrintStream
C - Closed. Closing Socket
C - Closed

NormR1 563 Posting Sage Team Colleague · Answer 6 · 2011-09-20T04:28:08+00:00

Do you have messages for all the calls to close()?

Here's what I get after a few code changes:

Client starting
Server Started: ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=5555]
S - Client Connected: Socket[addr=/192.168.1.10,port=4415,localport=5555]
C msg=Server: Hello
S - Connection from : /192.168.1.10
S read=Client: Hi Server

sirlink99 56 Practically a Master Poster · Answer 7 · 2011-09-20T04:31:50+00:00

sirlink99 56 Practically a Master Poster

12 Years Ago

I do have printlns before and after each close().

Edited 12 Years Ago by sirlink99 because: n/a

NormR1 563 Posting Sage Team Colleague · Answer 8 · 2011-09-20T04:37:06+00:00

I don't know why your printed "closing" message doesn't print out before the "Socket is closed" message.

When I restore the code I get:

Client starting
Server Started: ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=5555]
S - Client Connected: Socket[addr=/192.168.1.10,port=4622,localport=5555]
C msg=Server: Hello
C closing PS
C closing socket
C socket closed
S closing PS
S - Connection from :  /192.168.1.10
java.net.SocketException: Socket is closed
	at java.net.Socket.getInputStream(Socket.java:788)
	at ClientServerSockets$ServerSockets.<init>(ClientServerSockets.java:61)
	at ClientServerSockets$1.run(ClientServerSockets.java:17)
	at java.lang.Thread.run(Thread.java:662)

0 error(s)

sirlink99 56 Practically a Master Poster · Answer 9 · 2011-09-20T04:44:21+00:00

here is my code that has all of the printlns in it

Server

package BasicNIO;

import java.io.*;
import java.net.*;
import java.nio.*;

public class ServerSockets {

	ServerSocket servSock;
	Socket sock;
	
	public ServerSockets (){
		
		// creates a new server socket at port 5555
		try {
			servSock = new ServerSocket (5555);
			 System.out.println("S - Server Started: " + servSock);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		// creates a socket that uses the server socket
		
		 try {
			System.out.println ("S - Waiting for a Connection");
			sock = servSock.accept();
			System.out.println ("S - Connection Accepted");
			System.out.println("Client Connected: " + sock);
			PrintStream ps = new PrintStream (sock.getOutputStream ());
			System.out.println ("S - Sending message");
			ps.println ("Server: Hello"); // sends message
			System.out.println ("S - Message Sent");
			ps.close(); // closes print stream
			System.out.println ("S - PrintStream Closed");
			
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		 System.out.println(" Connection from :  " + sock.getInetAddress());
		 System.out.println ("S - Entering reading try-catch statement");
		  try {
			System.out.println ("S - Creating DataInputStream");
			DataInputStream is = new DataInputStream(sock.getInputStream());
			System.out.println ("S - Created! Trying to recieve Message");
			System.out.println(is.readLine());
			System.out.println ("S - Closing socket");
			sock.close();
			System.out.println ("S - Socket Closed");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
	
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		ServerSockets ss = new ServerSockets ();
		
		
	}

}

Client

package BasicNIO;

import java.io.*;
import java.net.*;
import java.nio.*;

public class Sockets {

	Socket sock;
	
	public Sockets (){
		InetAddress ip;
		try {
			System.out.println ("C - Setting up address");
			ip = InetAddress.getByName
			 ("192.168.0.100");
			System.out.println ("C - Creating socket");
			sock = new Socket (ip,5555);
			System.out.println ("C - Socket Created");
		} catch (UnknownHostException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		try {
			System.out.println ("C - Creating PrintStream");
			PrintStream ps = new PrintStream(sock.getOutputStream());
			System.out.println ("C - Created! Sending Message");
			ps.println ("Client: Hi Server");
			System.out.println ("C - Message Sent");
			System.out.println ("C - Creating DataInputStream");
			DataInputStream is = new DataInputStream(sock.getInputStream());
			System.out.println ("C - Created. Attempting to read message");
			String message = is.readLine();
			System.out.println ("C - Message read, and assigned to a variable 'message'");
			System.out.println ("C - Printing message");
			System.out.println (message);
			System.out.println ("C - Message Printed. Closing DataInputStream");
			is.close();
			System.out.println ("C - Closed. Closing PrintStream");
			ps.close();
			System.out.println ("C - Closed. Closing Socket");
			sock.close();
			System.out.println ("C - Closed");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public static void main (String [] args){
		Sockets s = new Sockets ();
		
		
		
	}
	
}

NormR1 563 Posting Sage Team Colleague · Answer 10 · 2011-09-20T04:51:06+00:00

Sorry, no idea what is happening on your system.
When I removed all the close() calls it worked for me.

sirlink99 56 Practically a Master Poster · Answer 11 · 2011-09-20T07:37:56+00:00

even if I take out all of the close() statements it still doesn't work

NormR1 563 Posting Sage Team Colleague · Answer 12 · 2011-09-20T07:40:21+00:00

Strange it works for me. Here's my working version:

/*http://www.daniweb.com/software-development/java/threads/383023/1649558#post1649558

*/


//package BasicNIO;

import java.io.*;
import java.net.*;
import java.nio.*;

public class ClientServerSockets {

	public static void main(String[] args) {
      Thread t = new Thread(new Runnable() {
        public void run() {
		    ServerSockets ss = new ServerSockets ();
        }
      });
      t.start();
 
		Sockets s = new Sockets ();
   }



static class ServerSockets {

	ServerSocket servSock;
	Socket sock;
	
	public ServerSockets (){
		
		// creates a new server socket at port 5555
		try {
			servSock = new ServerSocket (5555);
			 System.out.println("Server Started: " + servSock);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		// creates a socket that uses the server socket
		
		 try {
			sock = servSock.accept();
			System.out.println("S - Client Connected: " + sock);
			
			PrintStream ps = new PrintStream (sock.getOutputStream ());
			ps.println ("Server: Hello"); // sends message
//         System.out.println("S closing PS");
//			ps.close(); // closes print stream
			
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

		 System.out.println("S - Connection from :  " + sock.getInetAddress());
		 
		  try {
			DataInputStream is = new DataInputStream(sock.getInputStream());  // Socket closed here
			System.out.println("S read=" + is.readLine());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		try {
			sock.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} // closes socket connection
	}
	
	

}
/*
package BasicNIO;

import java.io.*;
import java.net.*;
import java.nio.*;
*/
static class Sockets {

	Socket sock;
	
	public Sockets (){
      System.out.println("Client starting");
		InetAddress ip;
		try {
			ip = InetAddress.getByName("192.168.1.10"); //192.168.0.100");
			sock = new Socket (ip, 5555);
		} catch (UnknownHostException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		try {
			PrintStream ps = new PrintStream(sock.getOutputStream());
			ps.println ("Client: Hi Server");
			DataInputStream is = new DataInputStream(sock.getInputStream());
			String message = is.readLine();
			System.out.println ("C msg=" + message);
//         System.out.println("C closing PS");
//			ps.close();
//         System.out.println("C closing socket");
//			sock.close();
//         System.out.println("C socket closed");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

} // end class

Sockets and relaying messages

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