Multi homeing with java sockets.

suppose i have N different NIC's in my machine,each with its own IP Address.
I want to listen on port# X on all the NIC's.
does i have to feed every IP Address to the Socket I want it listen to that port,or there's some method or trick so that Java Socket can find itself all the IP's associated with my machine?

So the OS itself looks for every IP assigned to machine and Java and JVM will get it from the OS?Not in this case. The OS or rather TCP/IP binds the listening socket to the 'wildcard' address which matches any IP address of the host, so when a connection comes in on that port via any NIC it will be despatched to the listening socket.
ServerSocket listner=new
ServerSocket(port);
now running :
listner.accept()
returns an array of Sockets each bined to a specific
IP?No, there is only a single listening socket, and accept() returns a single Socket for every incoming connection.
What about DatagramSockets if I want to listen for
UDP packets?Same principle. Don't bind it to any local IP address, or bind it to the null address which is Java's way of expressing the wildcard address.

Similar Messages

Performance problems with java sockets

Hi ,
I written a server class that simply writes the numbers and the client simply reads those numbers and prints them. When I run the both client and server on tha same machine there is no data loss found. But when I run the server on different machine than client I found heavy dataloss.(while theserver written numbers from 1-9000 the client is able read only 6000 plus). The data loss is increased when the data read from the server socket created by the VB application. Here with i am pasting the code snippet for the Server and the Client java files . Please help me in solving this problem.
Client.java
import java.net.*;
import java.io.*;
public class Client
     static Socket client = null;
     ObjectInputStream is = null;
     public Client() throws Exception
          client = new Socket("rajsekhar",3333);
          is = new ObjectInputStream (client.getInputStream());
          while(true){
               Integer in = (Integer)is.readObject();
               System.out.println(in.toString());
     public static void main(String[] args) throws Exception
          new Client();
Server.java
import java.net.*;
import java.io.*;
public class Server
     public static void main(String[] args) throws Exception
          ServerSocket server = null;
          server = new ServerSocket(3333);
          Socket s = server.accept();
          ObjectOutputStream os = new ObjectOutputStream(s.getOutputStream());
          int i =1;
          while(true)
               os.writeObject(new Integer(i));
               System.out.println(i);
               i++;
please help me .
thanks in advance,
Sridhar Reddy .R

Hi,
Try putting os.flush() after doing the writting... I mean:
os.writeObject(new Integer(i));
os.flush();
Good Luck!

BGP multi-homing with two different providers – iBGP and traversal question.

I have two internet connections. Both connections are with different providers and on two separate routers. I have two ASA’s that sit behind the routers and I proxy arp all hosted services off of the ASA’s outside interface.
I am obtaining a provider independent AS number from ARIN and would like to setup eBGP peering with each provider, accepting a default route only and advertise my leased block (let’s say 50.100.150.0/24). I’d like to prepend my AS on the ISP-B connection to ensure that it is only used as backup.
Here is the real question. I know I will need to allow TCP-179 through the ASA’s to establish the iBGP connection but because the hosts that I have at site A are proxy-arp’d off of the firewall outside interface, I need some way for traffic to come in from ISP-B, to router B and then traverse over to router A so that it can be sent to ASA-Firewall A. (please see attached diagram). What is the best way to accomplish this? GRE tunnel between the routers & through the firewalls? I have ample bandwidth and low latency between site A and B.
Thanks

Is that orange line a direct connection between CPE routers? If yes, a direct iBGP connection is possible. If not, I suggest that you obtain one as it is almost impossible to make the ASAs stay in sync with BGP routing. (-: If you can't, then GRE could be a workaround.
Is ASA redundancy a requirement too? (I mean in case ASA-A fails, are the site-A servers supposed to be accessible via ASA-B?) If yes, you must ensure that the outgoing traffic (default route in internal network) is in sync with active ISP and asymmetric routing is prevented. You can solve that with object tracking and you need the same static NATs in both ASAs.
I would consider creating shared VLANs on ASA interfaces and form a failover pair too but it's a different setup.

How to control tcp connection with java tcp socket programing ??

Hi,
I am connecting a server as using java socket programming.
When server close the connection (socket object) as using close() method ,
I can not detect this and My program continue sending data as if there is a connection with server.
How to catch the closing connection ( socket ) with java socket programming.
My Client program is as following :
import java.io.PrintWriter;
import java.net.Socket;
public class client
public client()
   * @param args
public static void main(String[] args)
    Socket socket=null;
    PrintWriter pw=null;
    try
                      socket = new Socket("localhost",5555);
                      pw = new PrintWriter(socket.getOutputStream(),true);
                      int i=0;
                      while (true)
                        i++;
                        pw.println(i+". message is being send.");
                        Thread.sleep(5000);
    } catch (Exception ex)
                      ex.printStackTrace();
    } finally
                      try
                        if(pw!=null)pw.close();
                        if(socket!=null)socket.close();
                      } catch (Exception ex)
                        ex.printStackTrace();
                      } finally
}

I changed the code as following. But I couldn't catch the EOFException when I read from the socket. How can I catch this exception ?
import java.io.BufferedReader;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
public class client
public client()
   * @param args
public static void main(String[] args)
    Socket socket=null;
    PrintWriter pw=null;
    BufferedReader bufIn=null;
    InputStreamReader inRead=null;
    InputStream in=null;
    try
                      socket = new Socket("localhost",5555);
                      in = socket.getInputStream();
                      inRead = new InputStreamReader(in);
                      bufIn = new BufferedReader(inRead);
                      pw = new PrintWriter(socket.getOutputStream(),true);
                      int i=0;
                      while (true)
                        i++;
                        try
                          bufIn.readLine();
                          pw.println(i+". message is being send.");
                          System.out.println(i+". message has been send");
                        } catch (Exception ex2)
                          System.out.println(ex2.toString());
                          System.out.println(i+". message could not be send");
                        } finally
                        Thread.sleep(5000);
    } catch (EOFException ex)
                      ex.printStackTrace();
    } catch (InterruptedException ex)
                      ex.printStackTrace();
    } catch (IOException ex)
                      ex.printStackTrace();
    } finally
                      try
                        if(pw!=null)pw.close();
                        if(socket!=null)socket.close();
                      } catch (Exception ex)
                        ex.printStackTrace();
                      } finally
}

Java sockets and raw sockets

Hello!
I have made my own file sharing program with Java sockets
and i have read a litle bit about raw sockets also.
What are the differences between Java sockets and raw sockets?

raw socket can have packet types which Java does not.
Generally if you need something useful which Java cannot do there is a utility already written which does what you want, e.g. ping and you can call that.

AF_UNIX socket with java

Is there any way to use unix domain sockets with java ? Is it level of socket abstraction implementation to high ? I guess it's not possible to use such functionality without JNI, but if so i'll be very happy. If it's not possible to do it without JNI can you suggest some libraries ?

I really don't understand your question because based on my rudimentary socket knowledge a AF_UNIX socket is a Java socket when you are running on a Unixy system.
No?
Because Uniz sockets have two flavours socket stream (which I believe is the standard Java Socket) and datagram thingies (which are also available as DatagramSockets in Java)
So is there something I am missing here? Are these like interprocess pipes? Sorry if I am clueless but I don't understand what you are asking.

Java Sockets - help with using objects

I am new to java sockets, and need to come up with a way to send a user defined instance of a class across a basic client/server application.
I can not find out how to do this. I read the tutorials, but my class can not be serialized. How can I send/recieve this instance of a user defined class?

right off the top of my head, doesn't serialver just spit out a UID for a given set of classes?
To mark a class as Serializable, just implement the java.io.Serializable class - then you could use the readObject/writeObject methods of the ObjectInputStream/ObjectOutputStream classes.
Good luck
Lee

Use of synchronized queue for java socket communications

Hi all,
We have a need for a server socket application (stand alone java application) to process just one command per time coming from a java socket client (JSP Web application). There are a lot of users accessing the java socket client, but the server socket can only handle one command per time, so there is a need of a queue type, so users will have to wait for their time.
We've been told that we can use "synchronized Queue", but we don't know what it is and how to use. A URL, book etc. with sample code would assist us, since we are new to both java socket communication and queue of commands.
Can anyone assist us
cheers
Trajano
P.S.
The server socket java application has two threads:
1st thread handles the java socket communication;
2nd thread is a RS-232 serial driver that communicates to several micro-controllers connected on a multi-drop.
JSP web app client socket users can issue various commands at the same time to the java server socket app, however the server can only service one command per time (just one RS-232 COM1 serial port available). The commands have to somehow be added to a queue for processing.

I do not have the experience to offer advice. But I just happened to be reading today about Collections.synchronizedList.
import java.util.List;
import java.util.LinkedList;
import java.util.Collections;
public class Queue {
   private List queue;
   public Queue() {
      queue = Collections.synchronizedList(new LinkedList());
   public Object removeItem() throws InterruptedException {
      synchronized (queue) {
         while (queue.isEmpty())
            queue.wait();
         return queue.remove(0);
   public void addItem(Object item) {
      synchronized (queue) {
         queue.add(item);
         queue.notifyAll();
class Test {
   public static void main(String[] args) {
      final Queue queue = new Queue();
      //start a thread to process items from the queue
      Runnable work = new Runnable() {
         public void run() {
            try {
               Object item = queue.removeItem();
               //do something with item
            } catch (InterruptedException e) {
               //handle this
      Thread worker = new Thread(work);
      worker.start();
}Reference: Java Thread Programming, Paule Hyde
Also, here is Doug Lea's library,
http://gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html

Problem with java swing button and loop

Problem with java swing button and loop
I�m using VAJ 4.0. and I�m doing normal GUI application. I have next problem.
I have in the same class two jswing buttons named start (ivjGStart) and stop (ivjGStop) and private static int field named Status where initial value is 0. This buttons should work something like this:
When I click on start button it must do next:
Start button must set disenabled and Stop button must set enabled and selected. Field status is set to 1, because this is a condition in next procedure in some loop. And then procedure named IzvajajNeprekinjeno() is invoked.
And when I click on stop button it must do next:
Start button must set enabled and selected and Stop button must set disenabled.
Field status is set to 0.
This works everything fine without loop �do .. while� inside the procedure IzvajajNeprekinjeno(). But when used this loop the start button all the time stay (like) pressed. And this means that a can�t stop my loop.
There is java code, so you can get better picture:
/** start button */
public void gStart_ActionEvents() {
try {
ivjGStart.setEnabled(false);
ivjGStop.setEnabled(true);
ivjGStop.setSelected(true);
getJTextPane1().setText("Program is running ...");
Status = 1;
} catch (Exception e) {}
/** stop button */
public void gStop_ActionEvents() {
try {
ivjGStart.setEnabled(true);
ivjGStart.setSelected(true);
ivjGStop.setEnabled(false);
getJTextPane1().setText("Program is NOT running ...");
Status = 0;
} catch (Exception e) {
/** procedure IzvajajNeprekinjeno() */
public void IzvajajNeprekinjeno() { //RunLoop
try {
int zamik = 2000; //delay
do {
Thread.sleep(zamik);
PreberiDat(); //procedure
} while (Status == 1);
} catch (Exception e) {
So, I'm asking what I have to do, that start button will not all the time stay pressed? Or some other aspect of solving this problem.
Any help will be appreciated.
Best regards,
Tomi

This is a multi thread problem. When you start the gui, it is running in one thread. Lets call that GUI_Thread so we know what we are talking about.
Since java is task-based this will happen if you do like this:
1. Button "Start" is pressed. Thread running: GUI_Thread
2. Event gStart_ActionEvents() called. Thread running: GUI_Thread
3. Method IzvajajNeprekinjeno() called. Thread running: GUI_Thread
4. Sleep in method IzvajajNeprekinjeno() on thread GUI_Thread
5. Call PreberiDat(). Thread running: GUI_Thread
6. Check status. If == 1, go tho 4. Thread running: GUI_Thread.
Since the method IzvajajNeprekinjeno() (what does that mean?) and the GUI is running in the same thread and the event that the Start button has thrown isn't done yet, the program will go on in the IzvajajNeprekinjeno() method forever and never let you press the Stop-button.
What you have to do is do put either the GUI in a thread of its own or start a new thread that will do the task of the IzvajajNeprekinjeno() method.
http://java.sun.com/docs/books/tutorial/uiswing/index.html
This tutorial explains how to build a multi threaded gui.
/Lime

Multi threadin with VC++

Multi threadin with VC++
I have some problems with multi threading using the provider OraOLEDB.
When I try to execute a CreateCommand for a CCommand<CManualAccessor> in a secondary thread I have a failure inside OraOLEDB.dll.
There is no problem if I use the provider MSDAORA.
I found a property for the OLE DB provider named DBPROP_DSOTHREADMODEL and must be DBPROPVAL_RT_FREETHREAD,
is the provider OraOLEDB FREETHREAD?
Thanks for helping me.

Do I have this right?
You want to start a Java application from the commandline, and this application creates multiple threads.
Each thread executes methods from the ProcessBuilder or Runtime classes, which opens a terminal (cmd) window, starts an external (non-Java) .exe program. The exe writes to the cmd window.
If that's correct, then you need to learn how to create a threaded program, and to use Either the ProcessBuilder or Runtime class.
Here's a how-to on creating threaded (concurrent) Java programs
http://java.sun.com/docs/books/tutorial/essential/concurrency/index.html
and here's an article on correct use of the Runtime class
http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html

Problem with the socket and the standard output stream

Hy, I have a little problem with a socket program. It has the server and the client. The problem is that the client at one point in the program, cannot print messages in the console.
My program does the next: the server waits connections, when a client connects to it, the server gets outputstream to the socket and writes two strings on it. Meanwhile, the client gets the inputstream to the socket and reads on it with a loop the two strings written by the server . The strings are printed by the client in the console. The problem starts here; once the read strings are printed ,I mean, after the loop, there are other System.out.println in the client but the console doesnt print anything . It curious that only when I comment on the server code the line that says: "br.readLine()" just before the catch, the client prints all the System.out.println after the loop but why?
Here is the code:
Server code:
public class MyServerSocket {
public MyServerSocket() {
try{
ServerSocket server= new ServerSocket(2000);
System.out.println("servidor iniciado");
Socket client=server.accept();
System.out.println("Client connected");
OutputStream os=client.getOutputStream();
PrintWriter pw= new PrintWriter(os);
String cadena1="cadena1";
String cadena2="cadena2";
pw.println(cadena1);
pw.println(cadena2);
pw.flush();
InputStream is=client.getInputStream();
InputStreamReader isr= new InputStreamReader(is);
BufferedReader br= new BufferedReader(isr);
br.readLine(); //If a comment this line, the client prints after the loop, all the System.out....
catch (IOException e) {
// TODO: handle exception
public static void main(String[] args) {
new MyServerSocket
Client code:
public class MyClientSocket {
public MyClientSocket () {
try{
Socket client= new Socket("localhost",2000);
InputStream is=client.getInputStream();
InputStreamReader isr= new InputStreamReader(is);
BufferedReader br= new BufferedReader(isr);
String read;
while((read=br.readLine())!=null){
System.out.println(read);
//These messages are not printed unless I comment the line I talked about in the server code
System.out.println("leido");
System.out.println("hola");
}catch (IOException e) {
public static void main(String[] args) {
new MyClientSocket
}

You are right but with this program the loop ends. As you see, the first class, the Server, writes to the socket one text file. The second class, the client, reads the text file in his socket written by the server and writes it to a file in his machine.
NOTE: The loop in the client ends and the server doesnt make any close() socket or shutdownOutput() .
public class ServidorSocketFicheromio {
     public ServidorSocketFicheromio() {
try{
     ServerSocket servidor= new ServerSocket(2000);
     System.out.println("servidor iniciado");
     Socket cliente=servidor.accept();
     System.out.println("cliente conectado");
     OutputStream os=cliente.getOutputStream();
     PrintWriter pw= new PrintWriter(os);
     File f = new File("c:\\curso java\\DUDAS.TXT");
     FileReader fr= new FileReader(f);
     BufferedReader br= new BufferedReader(fr);
     String leido;
     while((leido=br.readLine())!=null){
          pw.println(leido);
     pw.flush();
     }catch (IOException e) {
     * @param args
     public static void main(String[] args) {
          new ServidorSocketFicheromio();
public class ClienteSocketFicheromio {
     public ClienteSocketFicheromio() {
try{
     Socket cliente= new Socket("localhost",2000);
     File f = new File("G:\\pepe.txt");
     FileWriter fw= new FileWriter(f);
     PrintWriter pw= new PrintWriter(fw);
     InputStream is=cliente.getInputStream();
     InputStreamReader isr= new InputStreamReader(is);
     BufferedReader br= new BufferedReader(isr);
     String leido;
     while((leido=br.readLine())!=null){
          pw.println(leido);
          System.out.println(leido);
          System.out.println("leido");
          System.out.println("hola");
          pw.flush();
     }catch (IOException e) {
     public static void main(String[] args) {
     new ClienteSocketFicheromio();/
}

Connection refused with java, but not javaw

I have a ServerSocket based program...listening on a port. It is really a very simple program. And I can run it with javaw. Then I can use another problem, for example, telnet to connect to that port, just to prove I can connect to that port. Everything is fine.
Now if I run the exactly the same ServerSocket program with java, then I got the connection refused error.
It is weird.
Do you know why? Do you know a good socket troubleshooting tool on Windows? I am afraid of the viruses, so I haven't downloaded any free tools yet.

You're right.
The Norton personal firewall does not handle localhost to localhost correctly. I do all the tests on the same machine. The netstat -an shows the port is listening in either case. But now I know the firewall blocks one of them silently. No rule prompt was triggered. Worse, no logging produced for that particular access.
Thanks. You've been very helpful.

Unable to map actionscripting with java nested objects

Hi Experts...,
Im a newbie in flex and actionscripting.....
Im unable to map nested java classes and objects with my front end flex application using actionscript....I have searched everywhere almost to my knowledge on the net but failed to find a fix...,
im having serious trouble reffereing to attributes of an object using another object( which by the way happens to be the parent object).
Im using hibernate and springs to do the DB transactions....,
Please help me out with this issue.....
Thanks for all the help and support in advance....

Again, I don't work with Java and you should ask Java-related question in Flex (or Java) forum.
Java or not - you need to package your server side language specific object into something that AS understands (text, XML, AMF object) and load this data into AS via, perhaps, URLLoader. Or you can open socket. Then you parse this data with AS3 code in SWF.

Sending Emails With Java

I'm trying to find out how to send emails with java - without using the java mail api - i've been told there is a way to do it but i cant seem to find it - any help on this would be gratefully recieved as i'm totally stuck! :(

Ok, I expanded on it a little bit. Still probably isnt totally correct.
String localhost="yourdomain.com";
String sendMailHost=�mail.domain.com�;
int portNo=25;
String from="[email protected]";
String to="[email protected]";
String message=�Message Body.�;
Socket s = new Socket(SendMailHost,portNo);
DataInputStream in = new DataInputStream(s.getInputStream() ) ;
PrintStream out = new PrintStream(s.getOutputStream() ) ;
out.println("HELO " + locahost);
out.flush() ;
in.readLine(); //ignore response
out.println("MAIL FROM: " + from);
out.flush() ;
in.readLine(); //ignore response
out.println("RCPT TO: " + to);
out.flush() ;
in.readLine(); //ignore response
out.println("DATA");
out.println(message);
out.println(�.�);
s.close();

Offline Web Start app fails to launch with Java 7 Update 25

So it seems that another issue with Java 7 update 25 and Web Start applications is that a signed application will not launch when offline.
It fails when attempting to check the revocation status of the signing certificate.
Anyone have any ideas to get around this exception aside from uninstalling update 25?
Thanks!
com.sun.deploy.security.RevocationChecker$StatusUnknownException: java.net.UnknownHostException: ocsp.usertrust.com
               at com.sun.deploy.security.RevocationChecker.checkOCSP(Unknown Source)
               at com.sun.deploy.security.RevocationChecker.check(Unknown Source)
               at com.sun.deploy.security.TrustDecider.checkRevocationStatus(Unknown Source)
               at com.sun.deploy.security.TrustDecider.getValidationState(Unknown Source)
               at com.sun.deploy.security.TrustDecider.validateChain(Unknown Source)
               at com.sun.deploy.security.TrustDecider.isAllPermissionGranted(Unknown Source)
               at com.sun.javaws.security.AppPolicy.grantUnrestrictedAccess(Unknown Source)
               at com.sun.javaws.security.JNLPSignedResourcesHelper.checkSignedResourcesHelper(Unknown Source)
               at com.sun.javaws.security.JNLPSignedResourcesHelper.checkSignedResources(Unknown Source)
               at com.sun.javaws.Launcher.prepareResources(Unknown Source)
               at com.sun.javaws.Launcher.prepareAllResources(Unknown Source)
               at com.sun.javaws.Launcher.prepareToLaunch(Unknown Source)
               at com.sun.javaws.Launcher.prepareToLaunch(Unknown Source)
               at com.sun.javaws.Launcher.launch(Unknown Source)
               at com.sun.javaws.Main.launchApp(Unknown Source)
               at com.sun.javaws.Main.continueInSecureThread(Unknown Source)
               at com.sun.javaws.Main.access$000(Unknown Source)
               at com.sun.javaws.Main$1.run(Unknown Source)
               at java.lang.Thread.run(Unknown Source)
               Suppressed: com.sun.deploy.security.RevocationChecker$StatusUnknownException
                              at com.sun.deploy.security.RevocationChecker.checkCRLs(Unknown Source)
                              ... 18 more
Caused by: java.net.UnknownHostException: ocsp.usertrust.com
               at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
               at java.net.PlainSocketImpl.connect(Unknown Source)
               at java.net.SocksSocketImpl.connect(Unknown Source)
               at java.net.Socket.connect(Unknown Source)
               at sun.net.NetworkClient.doConnect(Unknown Source)
               at sun.net.www.http.HttpClient.openServer(Unknown Source)
               at sun.net.www.http.HttpClient.openServer(Unknown Source)
               at sun.net.www.http.HttpClient.<init>(Unknown Source)
               at sun.net.www.http.HttpClient.New(Unknown Source)
               at sun.net.www.http.HttpClient.New(Unknown Source)
               at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
               at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
               at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
               at sun.net.www.protocol.http.HttpURLConnection.getOutputStream(Unknown Source)
               at sun.security.provider.certpath.OCSP.check(Unknown Source)
               at sun.security.provider.certpath.OCSP.check(Unknown Source)
               at sun.security.provider.certpath.OCSP.check(Unknown Source)
               ... 19 more

Disregard. I found that the user had changed the java security settings to "Very High" in addition to upgrading to update 25.

Multi homeing with java sockets.

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