Re:Applet socket communication

Hi guys,
Is it possible to get two applet windows one on the client side and other on the remote using only the Socket() class.
Actually we have a game in which it is connecting to a server and write some commands to that server.based on the commands applet windows should appear both in client as well as in remote.
Can anybody tell me about this.

1) There will be no remote server applet. One of the clients will have to run it. Applets are always executed on the client only.
2) For applets communicating with anything else but the server they came from, they need to be signed.

Similar Messages

Applet socket communication

Hello,
I've successfully created a simple client-server application that communicate through the socket,
and now converting to applet, but the following error occured on the java console
java.security.AccessControlException: access denied (java.net.SocketPermission 203.xxx.xxx.xxx:9800 connect,resolve)
that's also the web server where the applet is downloaded
when i try my computer to run the applet (changed the socket ip to 127.0.0.1 or 192.168.0.111 and run the server app) it works just fine..
but when i changed it to the public IP and put it on the webserver that's what happen..
is there any way beside change the policy?
can anyone please help?
I'm really in a big need of help
thank you..
Edited by: bigpappa on Mar 17, 2009 4:05 AM

1) There will be no remote server applet. One of the clients will have to run it. Applets are always executed on the client only.
2) For applets communicating with anything else but the server they came from, they need to be signed.

Socket communication failure between Java applet and C++ application

I have a java applet that connects to a C++ application via Java's ServerSocket and Socket objects. THe C++ application is using the Winsock 2 API. The applet and application are running on an NT workstation (SP 6) and using IE (5.5) For a very simple C++ test applications the communictions work fine. Once more code gets added to the C++ application the portion of the socket that C++ listens to seems to close. Upon performing a recv call the return value is a zero. Microsoft insists this is a sign the Java side has shut down the socket. The Java applet can still receive messages from the C++ app but C++ cannot receive responses from the Java side. Java throws no exceptions and an explicit check of the socket shows no errors. Again, what puzzles me is that it works for simple C++ applications. Are there any known conflicts between Java and C++ in this regard?
I have inlcuded the basic java code segments below.
/ run Method.
* This method is called by the Thread.start() method. This
* method is required for the implementation of the Runnable interface
* This method sets up the server side socket communication and
* contiuously loops looking for requests from a external
* socket.
* @author Chris Duke
public void run(){
     // create socket connections
     boolean success = false;
     try {
         cServerSocket = new ServerSocket(cPortID);
         System.out.println("Waiting for client to connect...");
         cClientSocket = cServerSocket.accept();
         System.out.println("Client connected");
         // Create a stream to read from the client
         cInStream = new BufferedReader(new InputStreamReader(
           cClientSocket.getInputStream()));
         // Create a stream to write to the client
         cOutStream = new PrintWriter(
           cClientSocket.getOutputStream(), true);
         success = true;
     }catch (IOException e) {
         System.out.println("CommSocket:Run - Socket Exception(1) " + e);
         success = false;
     // if the socket was successfully created, keep the thread running
     while (success){
         try{
            // check socket to see if it is still available for reading
            if (cInStream != null && cInStream.ready()){
                // check for an incoming message
                String message = ReceiveMessage();
                // Send message to listeners
                Event(message);
            if (cInStream == null){
                success = false;
                System.out.println("CommSocket:Run - shutdown");
         }catch (IOException e){
            System.out.println("CommSocket:Run - Socket not ready exception");
            break;
// SendMessage method -
* Sends a text message to a connected listener through port specified by portID
* @author Chris Duke
* @param String message - This will be the message sent out through the server
* socket's port specified by portID.
   public void SendMessage(String message){
      cOutStream.println(message);
      if (cOutStream.checkError() == true)
        System.out.println("SendMessage : Flush = Error");
      else{
        System.out.println("SendMessage : Flush - No Error");
   }

a very simple C++ test applications the communictions work fine. Once more code gets added to the C++ application the portion of the socket that C++ listens to seems to close.
This quite strongly implicates the extra code in the C++ App. The firstly thing I would try would be telnet. Try connecting to both versions of the C++ Application and manually reproducing a proper exchange.
a recv call the return value is a zero. Microsoft insists this is a sign the Java side has shut down the socket.
A correct implementation of recv should return the number of bytes received, or -1 for an error. A zero return indicates no bytes received not a socket closed/error. This sounds like FUD to me.
Are there any known conflicts between Java and C++ in this regard?
I can see no obvious faults, though the code is incomplete, I don't think it's an sockets implementation issue, at either end, it sounds more likely to be a protocol/handshaking bug in the C++ App.

Socket communication problem

hello all,
i have written a small program to send a message to echo server and get back the response from the server.
it gives a error as
COULD NOT GET I/O FOR CONNECTION TO <ip address>
i am working on win nt version 4 service pack 4 installed on a home computer.
the code is as below:
import java.io.*;
import java.net.*;
public class net4a {
public static void main(String[] args) throws IOException{
Socket echoSocket = null;
DataOutputStream os = null;
DataInputStream is = null;
 DataInputStream stdIn = new DataInputStream(System.in);
 InetAddress host = InetAddress.getLocalHost();
try {
echoSocket = new Socket(host, 7);
os = new DataOutputStream(echoSocket.getOutputStream());
is = new DataInputStream(echoSocket.getInputStream());
} catch (UnknownHostException e) {
System.err.println("Don't know about host: " + host);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: " + host);
if (echoSocket != null && os != null && is != null) {
try {
String userInput;
while ((userInput = stdIn.readLine()) != null) {
os.writeBytes(userInput);
os.writeByte('\n');
System.out.println("echo: " + is.readLine());
os.close();
is.close();
echoSocket.close();
} catch (IOException e) {
System.err.println("I/O failed on the connection to: " + host);
look forward to ur valuable tips on the same.

Hello,
Long time java programmer, first time forum user.
Looks like you looking to looking to get a java applet/program communicating with a web server. This is not an extremely difficult task and I have successfully got apache communicating CGI transactions to and from an applet with no drama�s.
This is very useful as it is restrictive to have to open up extra sockets across a network as many networks today restrict socket communication often for security or business/organization policies.
An alternative is to use HTTP request using the POST command to talk to a web server with the web server replying to the request. For example, you may need to ask a database to pull out all customer names from a server-side database. The applet need only send a URLEncoded request to the server, the webserver invokes the CGI process (I use Java to handle the CGI requests but other methods/languages can be used) which returns the result of the transaction.
I have listed some code that included the a �ping-pong� request to a server. It included the applet function that calls the webserver, the CGI batch script (for win NT/XP) to invoke the java program, the cgi-lib to simply parse the URL request (many thanks to the author) and the server-side java program that responds to the request.
I hope you find this useful. The download for apache, the webserver, is available at
http://www.apache.org/
and is a pretty simple install. Make sure you fix up the httpd.conf file to suit your system.
Good luck.
Dale Miller
CLIENT-SIDE (Java Applet Snippit)
public class Comm {
 private String server;
 private URL toServer;
 private URLConnection uRLConnection;
 private DataOutputStream dataOutputStream;
 private StringBuffer output;
 private BufferedReader dataInputStream;
 private String result;
 private int resultsLast;
 private String results[] = new String[100];
 private int firstTU;
 //this function starts in its own thread and takes care
 //of logins and there re-tries, the messaging.
 //Please see the actual function for better details
 //private LoginWatcher loginWatcher;
 public Comm(String serverAddress) throws UnsupportedEncodingException{
 System.out.println("loaded Comm class!");
 //First thing we need to do is set up the login watcher
 //loginWatcher = new LoginWatcher();
 this.output = new StringBuffer();
 this.server = serverAddress;
 try {
 this.toServer = new URL(server + "ping.cgi");
 } catch (MalformedURLException e) {
 System.out.println("ERROR : in contacting the server");
 System.out.println("Server : " + server);
 System.out.println("NOT FOUND!!");
 try {
 this.uRLConnection = toServer.openConnection();
 } catch (IOException e) {
 System.out.println("ERROR : Connection to server refused");
 this.uRLConnection.setUseCaches(false);
 this.uRLConnection.setDoInput(true);
 this.uRLConnection.setDoOutput(true);
 this.uRLConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
 try {
 this.dataOutputStream = new DataOutputStream(uRLConnection.getOutputStream());
 } catch (IOException e) {
 System.out.println("ERROR : opening dataoutputstream");
 this.output.setLength(0);
 output.append("first=" + URLEncoder.encode("I am", "UTF-8"));
 output.append("&last=" + URLEncoder.encode("number 1", "UTF-8"));
 try {
 dataOutputStream.writeBytes(new String(output));
 } catch (IOException e) {
 System.out.println("ERROR : Sending string to cgi ping.cgi");
 try {
 this.dataInputStream = new BufferedReader(new InputStreamReader(uRLConnection.getInputStream()));
 } catch (IOException e) {
 System.out.println("ERROR : Setting up input stream");
 String grab = new String();
 System.out.print("Searching for server..");
 try {
 grab = dataInputStream.readLine();
 grab = dataInputStream.readLine();
 } catch (IOException e) {
 System.out.println("ERROR : Reciving ping data from server");
 if (grab.equals("pass")) {
 System.out.println("OK");
 } else {
 System.out.println("ERROR\n\nSERVER NOT FOUND!!!");
 System.exit(-1);
 //loginWatcher.loginWatcherTh.start();
CGI BATCH TO INVOKE CGI PROGRAM
#!java -cp c:\ss\ middle
CGI-LIB TO PARSE HTTP REQUESTS
import java.util.*;
import java.io.*;
* cgi_lib.java
* 
* Usage: This library of java functions, which I have encapsulated inside
* a class called cgi_lib as class (static) member functions,
* attempts to duplicate the standard PERL CGI library (cgi-lib.pl).
* You must invoke any Java program that uses this library from
* within a UNIX script, Windows batch file or equivalent. As you
* will see in the following example, all of the CGI environment
* variables must be passed from the script into the Java application
* using the -D option of the Java interpreter. This example
* UNIX script uses the "main" routine of this class as a
* CGI script:
* <pre>
* (testcgi.sh)
* #!/bin/sh
* java \
* -Dcgi.content_type=$CONTENT_TYPE \
* -Dcgi.content_length=$CONTENT_LENGTH \
* -Dcgi.request_method=$REQUEST_METHOD \
* -Dcgi.query_string=$QUERY_STRING \
* -Dcgi.server_name=$SERVER_NAME \
* -Dcgi.server_port=$SERVER_PORT \
* -Dcgi.script_name=$SCRIPT_NAME \
* -Dcgi.path_info=$PATH_INFO \
* cgi_lib
* </pre>
* Question and comments can be sent to [email protected].
* @version 1.0
* @author Pat L. Durante
class cgi_lib
* Parse the form data passed from the browser into
* a Hashtable. The names of the input fields on the HTML form will
* be used as the keys to the Hashtable returned. If you have a form
* that contains an input field such as this,
* <pre>
* &ltINPUT SIZE=40 TYPE="text" NAME="email" VALUE="[email protected]"&gt
* </pre>
* then after calling this method like this,
* <pre>
* Hashtable form_data = cgi_lib.ReadParse(System.in);
* </pre>
* you can access that email field as follows:
* <pre>
* String email_addr = (String)form_data.get("email");
* </pre>
* @param inStream The input stream from which the form data can be read.
* (Only used if the form data was posted using the POST method. Usually,
* you will want to simply pass in System.in for this parameter.)
* @return The form data is parsed and returned in a Hashtable
* in which the keys represent the names of the input fields.
public static Hashtable ReadParse(InputStream inStream)
Hashtable form_data = new Hashtable();
String inBuffer = "";
if (MethGet())
inBuffer = System.getProperty("cgi.query_string");
else
// TODO: I should probably use the cgi.content_length property when
// reading the input stream and read only that number of
// bytes. The code below does not use the content length
// passed in through the CGI API.
DataInput d = new DataInputStream(inStream);
String line;
try
while((line = d.readLine()) != null)
inBuffer = inBuffer + line;
catch (IOException ignored) { }
// Split the name value pairs at the ampersand (&)
StringTokenizer pair_tokenizer = new StringTokenizer(inBuffer,"&");
while (pair_tokenizer.hasMoreTokens())
String pair = urlDecode(pair_tokenizer.nextToken());
// Split into key and value
StringTokenizer keyval_tokenizer = new StringTokenizer(pair,"=");
String key = new String();
String value = new String();
if (keyval_tokenizer.hasMoreTokens())
key = keyval_tokenizer.nextToken();
else ; // ERROR - shouldn't ever occur
if (keyval_tokenizer.hasMoreTokens())
value = keyval_tokenizer.nextToken();
else ; // ERROR - shouldn't ever occur
// Add key and associated value into the form_data Hashtable
form_data.put(key,value);
return form_data;
* URL decode a string.
* Data passed through the CGI API is URL encoded by the browser.
* All spaces are turned into plus characters (+) and all "special"
* characters are hex escaped into a %dd format (where dd is the hex
* ASCII value that represents the original character). You probably
* won't ever need to call this routine directly; it is used by the
* ReadParse method to decode the form data.
* @param in The string you wish to decode.
* @return The decoded string.
public static String urlDecode(String in)
StringBuffer out = new StringBuffer(in.length());
int i = 0;
int j = 0;
while (i < in.length())
char ch = in.charAt(i);
i++;
if (ch == '+') ch = ' ';
else if (ch == '%')
ch = (char)Integer.parseInt(in.substring(i,i+2), 16);
i+=2;
out.append(ch);
j++;
return new String(out);
* Generate a standard HTTP HTML header.
* @return A String containing the standard HTTP HTML header.
public static String Header()
return "Content-type: text/html\n\n";
* Generate some vanilla HTML that you usually
* want to include at the top of any HTML page you generate.
* @param Title The title you want to put on the page.
* @return A String containing the top portion of an HTML file.
public static String HtmlTop(String Title)
String Top = new String();
Top = "<html>\n";
Top+= "<head>\n";
Top+= "<title>\n";
Top+= Title;
Top+= "\n";
Top+= "</title>\n";
Top+= "</head>\n";
Top+= "<body>\n";
return Top;
* Generate some vanilla HTML that you usually
* want to include at the bottom of any HTML page you generate.
* @return A String containing the bottom portion of an HTML file.
public static String HtmlBot()
return "</body>\n</html>\n";
* Determine if the REQUEST_METHOD used to
* send the data from the browser was the GET method.
* @return true, if the REQUEST_METHOD was GET. false, otherwise.
public static boolean MethGet()
String RequestMethod = System.getProperty("cgi.request_method");
boolean returnVal = false;
if (RequestMethod != null)
if (RequestMethod.equals("GET") ||
RequestMethod.equals("get"))
returnVal=true;
return returnVal;
* Determine if the REQUEST_METHOD used to
* send the data from the browser was the POST method.
* @return true, if the REQUEST_METHOD was POST. false, otherwise.
public static boolean MethPost()
String RequestMethod = System.getProperty("cgi.request_method");
boolean returnVal = false;
if (RequestMethod != null)
if (RequestMethod.equals("POST") ||
RequestMethod.equals("post"))
returnVal=true;
return returnVal;
* Determine the Base URL of this script.
* (Does not include the QUERY_STRING (if any) or PATH_INFO (if any).
* @return The Base URL of this script as a String.
public static String MyBaseURL()
String returnString = new String();
returnString = "http://" +
System.getProperty("cgi.server_name");
if (!(System.getProperty("cgi.server_port").equals("80")))
returnString += ":" + System.getProperty("cgi.server_port");
returnString += System.getProperty("cgi.script_name");
return returnString;
* Determine the Full URL of this script.
* (Includes the QUERY_STRING (if any) or PATH_INFO (if any).
* @return The Full URL of this script as a String.
public static String MyFullURL()
String returnString;
returnString = MyBaseURL();
returnString += System.getProperty("cgi.path_info");
String queryString = System.getProperty("cgi.query_string");
if (queryString.length() > 0)
returnString += "?" + queryString;
return returnString;
* Neatly format all of the CGI environment variables
* and the associated values using HTML.
* @return A String containing an HTML representation of the CGI environment
* variables and the associated values.
public static String Environment()
String returnString;
returnString = "<dl compact>\n";
returnString += "<dt>CONTENT_TYPE <dd>:" +
System.getProperty("cgi.content_type") +
": \n";
returnString += "<dt>CONTENT_LENGTH <dd>:" +
System.getProperty("cgi.content_length") +
": \n";
returnString += "<dt>REQUEST_METHOD <dd>:" +
System.getProperty("cgi.request_method") +
": \n";
returnString += "<dt>QUERY_STRING <dd>:" +
System.getProperty("cgi.query_string") +
": \n";
returnString += "<dt>SERVER_NAME <dd>:" +
System.getProperty("cgi.server_name") +
": \n";
returnString += "<dt>SERVER_PORT <dd>:" +
System.getProperty("cgi.server_port") +
": \n";
returnString += "<dt>SCRIPT_NAME <dd>:" +
System.getProperty("cgi.script_name") +
": \n";
returnString += "<dt>PATH_INFO <dd>:" +
System.getProperty("cgi.path_info") +
": \n";
returnString += "</dl>\n";
return returnString;
* Neatly format all of the form data using HTML.
* @param form_data The Hashtable containing the form data which was
* parsed using the ReadParse method.
* @return A String containing an HTML representation of all of the
* form variables and the associated values.
public static String Variables(Hashtable form_data)
String returnString;
returnString = "<dl compact>\n";
for (Enumeration e = form_data.keys() ; e.hasMoreElements() ;)
String key = (String)e.nextElement();
String value = (String)form_data.get(key);
returnString += "<dt>" + key + " <dd>:" +
value +
": \n";
returnString += "</dl>\n";
return returnString;
* The main routine is included here as a test CGI script to
* demonstrate the use of all of the methods provided above.
* You can use it to test your ability to execute a CGI script written
* in Java. See the sample UNIX script file included above to see
* how you would invoke this routine.
* Please note that this routine references the member functions directly
* (since they are in the same class), but you would have to
* reference the member functions using the class name prefix to
* use them in your own CGI application:
* <pre>
* System.out.println(cgi_lib.HtmlTop());
* </pre>
* @param args An array of Strings containing any command line
* parameters supplied when this program in invoked. Any
* command line parameters supplied are ignored by this routine.
public static void main( String args[] )
// This main program is simply used to test the functions in the
// cgi_lib class.
// That said, you can use this main program as a test cgi script. All
// it does is echo back the form inputs and enviroment information to
// the browser. Use the testcgi UNIX script file to invoke it. You'll
// notice that the script you use to invoke any Java application that
// uses the cgi_lib functions MUST pass all the CGI enviroment variables
// into it using the -D parameter. See testcgi for more details.
// Print the required CGI header.
System.out.println(Header());
// Create the Top of the returned HTML
// page (the parameter becomes the title).
System.out.println(HtmlTop("Hello World"));
System.out.println("<hr>");
// Determine the request method used by the browser.
if (MethGet())
System.out.println("REQUEST_METHOD=GET");
if (MethPost())
System.out.println("REQUEST_METHOD=POST");
System.out.println("<hr>");
// Determine the Base URL of this script.
System.out.println("Base URL: " + MyBaseURL());
System.out.println("<hr>");
// Determine the Full URL used to invoke this script.
System.out.println("Full URL: " + MyFullURL());
System.out.println("<hr>");
// Print all the CGI environment variables
// (usually only used while testing CGI scripts).
System.out.println(Environment());
System.out.println("<hr>");
// Parse the form data into a Hashtable.
Hashtable form_data = ReadParse(System.in);
// Print out each of the name/value pairs
// from sent from the browser.
System.out.println(Variables(form_data));
System.out.println("<hr>");
// Access a particular form value.
// (This assumes the form contains a "name" input field.)
String name = (String)form_data.get("name");
System.out.println("Name=" + name);
System.out.println("<hr>");
// Create the Bottom of the returned HTML page - which closes it cleanly.
System.out.println(HtmlBot());
SERVER-SIDE PROGRAM TO RETURN PING
import java.util.*;
import java.io.*;
class ping
 public static void main(String args[]) {
 System.out.println(cgi_lib.Header());
 Hashtable form_data = cgi_lib.ReadParse(System.in);
 String one = (String)form_data.get("first");
 String two = (String)form_data.get("last");
 boolean test;
 test = false;
 if (one.equals("I am")) {
 if (two.equals("number 1")) {
 test = true;
 if (test == true) {
 System.out.println("pass");
 } else {
 System.out.println("fail");
 //Datavasee
ENJOY :)

Asynchronous applet-servlet communication

Hi all,
I am trying to implement asynchronous applet-servlet communication and need your help. Anything would help(I tried with synchronous applet-servlet communication but doesn't solve my problem).
Thanks,

http://java.sun.com/docs/books/tutorial/networking/index.html
You can open a socket connection. Bother the client and the server
can have separate threads for reading and writing and that you gives you
asynchronous communication. Later, if you think the server is generating
too many threads and not scaling, you can use features of .java.nio to
make it more scalable:
java.nio.channels

Applet, Application communication

Hi
Someone tell me how to do applet, application communication.
I have one standalone application, running in server and receiving connection from applets and every min. the server has to send some data back to each apllet connected.
How to do it... any sample or reffernces please..
Thanks in advance
Tomy

Can you give me example codes using RMI / Socket
thanks

Chat Applet - Sockets - Server

Hello Fellows!
I hope u all r fine..
I am facing a problem in my client/sever application. The communication is Socket Based. i.e the server is using sockets and the client which is an Applet, uses sockets to communicate with the sever.
The application is working fine in the appletviewer. i.e the applet server communication, both can send and recieve messages.
BUT
When I use IE5 the client applet can send messages to the sever but is not able to read from the specified socket...
If Any one can help me out, i will be greatfull. If u need some code segment then let me know.
Looking forward for any suggestions.
Thanking You!
Ahmad.

Thanks!
for your contribution....
but now i realised that the problem is that the client socket thread is not running.
//////////////////////// Client Applet
public class Client extends Applet implements ActionListener
Thread thRead;
ClientSocket cs;
private Panel pnlHead = new Panel();
private Panel pnlMain = new Panel();
public static Vector vtrMembers;
public void init()
thRead = (Thread) new ClientSocket();
     cs = (ClientSocket) thRead;
     vtrMembers = new Vector();
thRead.start();
cs.out.println("INI ? INI");
////////////////////////////////////////Client scoket class
public class ClientSocket extends Thread
// public static Socket sClient;
public Socket sClient;
// A character-input stream to read from the socket.
public static BufferedReader in;
// A text-output stream to write to the socket.
public PrintWriter out ;
// String to store the input from the client
String strText;
// Boolean Flag to Check the read value
public boolean bFlag = true;
public ClientSocket ()
     try
     sClient = new Socket ("Ahmed" , 4000);
     // Initializing the Input straem used to read the socket.
in = new BufferedReader(new InputStreamReader(sClient.getInputStream()));
     // Initializing the Output straem used to write on the socket.
     out = new PrintWriter(sClient.getOutputStream(), true);
     catch (UnknownHostException uhe)
//     System.out.println (" Unknown Host Exception : " + uhe);
     catch (IOException ioe)
//     System.out.println (" I/O Exception : " + ioe);
public void run()
     for (;;)
     if (bFlag == true)
     Client.txtTry.setText("TRUE");
     else
     Client.txtTry.setText("False");
thRead.start() statment is executed but the thread does not stat running
because the text value is not set on the Client Applet.

Problem with socket communications

I am trying to put together a client server socket communication pair.
I have one application that runs in the background acting as a server and another that can be started and stopped that acts as a client.
I can start the server and create a server socket with no problem.
I can start the client and it connects to the server.
The server acknowledges the connection and appears to go into a blocking state waiting for the client to send another message.
The server blocks at the line
parent.logit("Waiting for message from EVR..... ");
The problem is that when the client sends another message, the server doesn't hear it.
I am not sure if the problem is with the client or server communication code.
If anyone out there is a socket communication guru, I would appreciate it if you could tell me what I am doing wrong.
Thanks
Server code:
import java.io.*;
import java.net.*;
public class EVRServer
    extends Thread
EVRDataLoader parent = null;
ServerSocket serverSock = null;
Socket clientSock = null;
BufferedReader reader = null;
BufferedWriter writer = null;
int evrPort = 0;
int retryLimit = 10;
int retryCount = 0;
boolean alive = false;
boolean killSocket = false;
boolean evrConnected = false;
boolean retry = true;
EVRListener evrListener = null;
//=============================================================================
// Full constructor
//=============================================================================
   * Full constructor.
   * @param dl DataLoader - Parent application
   * @param port int Socket port
public EVRServer(EVRDataLoader dl, int port)
    parent = dl;
    evrPort = port;
//=============================================================================
// Run method - Main thread executed by start() method
//=============================================================================
   * Main thread executed by start() method
public void run()
    while (retry)
      if (retryCount > retryLimit)
        retry = false;
      parent.logit("Retry count = " + retryCount);
      // Create new server socket connection
      if (serverSock == null)
        try
          serverSock = new ServerSocket(evrPort);
          parent.logit("Created Server Socket for EVR on port " + evrPort);
          alive = true;
          killSocket = false;
          evrConnected = false;
        catch (Exception e)
          parent.logit(
              "ERROR - Could not create Server socket connection for EVR: " +
              e.toString());
          killSocket = true;
          alive = false;
      // Create new client socket connection
      if (clientSock == null)
        try
          parent.logit("Waiting for EVR to connect");
          clientSock = null;
          clientSock = serverSock.accept();
          retryCount = 0;
          evrConnected = true;
          killSocket = false;
          parent.logit("EVR connected on server Socket Port " + evrPort);
        catch (Exception e)
          parent.logit("ERROR - Error accepting EVR connection: " + e.toString());
          killSocket = true;
        try
          reader = new BufferedReader(new InputStreamReader(
              clientSock.getInputStream()));
          writer = new BufferedWriter(new OutputStreamWriter(
              clientSock.getOutputStream()));
          parent.logit( "Created reader "+reader);
          parent.logit( "Created writer "+writer);
        catch (Exception e)
          parent.logit(
              "ERROR - creating reader or writer to EVR: " + e.toString());
          killSocket = true;
      int nullCount = 0;
      while (killSocket == false)
        try
          parent.logit("Waiting for message from EVR..... ");
//          sendMessage("Data Controller connected on port " + evrPort);
          String s = reader.readLine();
          parent.logit("EVR - Received message: " + s);
          if (s != null)
            parent.processEvrMessage( s);
          else
            sleep(1000);
            nullCount++;
            if (nullCount > 10)
              parent.logit("Exceeded retry limit: ");
              killSocket = true;
        catch (Exception ex)
          parent.logit("Error Reading from EVR: " + ex.toString());
          killSocket = true;
      parent.logit( "After while loop");
      evrConnected = false;
      try
        retryCount++;
        parent.logit("Closing EVR connection. ");
        reader.close();
        writer.close();
        clientSock.close();
        writer = null;
        reader = null;
        clientSock = null;
        try
          sleep(1000);
        catch (Exception ee)
          parent.logit("Error after sleep " + ee.toString());
      catch (Exception e)
        parent.logit("Error closing EVR server socket");
//=============================================================================
// Call this method to kill the client socket connection.
//=============================================================================
   * Call this method to kill the client socket connection.
public void killConnection()
    killSocket = true;
//=============================================================================
// Return RTM connected state
//=============================================================================
   * Return RTM connected state
   * @return boolean - Returns true if RTM is connected to server, false if not.
public boolean isRtmConnected()
    return evrConnected;
//=============================================================================
// Returns state of server socket.
//=============================================================================
   * Returns state of server socket.
   * @return boolean - Returns true if server socket is enabled, false if not.
public boolean isServerSocketAlive()
    return alive;
//=============================================================================
// Send a message to the client socket.
//=============================================================================
     * Send a message to the client socket.
     * @param msg String - Message to send.
     * @return boolean - Returns true if message sent OK, false if not.
public boolean sendMessage(String msg)
    parent.logit(" In EVR Server - Send Message - got message: " + msg);
    if (evrConnected)
      try
        parent.logit("Sending message to EVR: " + msg);
        writer.write(msg + "\n");
        writer.flush();
        return true;
      catch (Exception e)
        parent.logit("ERROR - Error sending message to EVR: " + e.toString());
        return false;
    else
      parent.logit("EVR not connected, cannot send message: " + msg);
      return false;
}Client code:
package evrsimulator;
import java.net.*;
import java.io.*;
class PortConnector
      extends Thread
   ServerSocket serverSock = null;
   boolean isIP = false;
   InetAddress addr = null;
   Frame1 parent = null;
   byte[] rawIP;
    //   String initialMsg = "";
   public PortConnector( Frame1 f )
     parent = f;
   // This method is called when the thread runs
   public void run()
      if ( parent.hostName.indexOf( "." ) > 0 )
         isIP = true;
         byte[] rawIP = parent.getRawIP( parent.hostName );
      try
         System.out.println( "Connecting to host " +
                                        parent.hostName + " on port " +
                                        parent.socketPort );
         if ( isIP )
            addr = InetAddress.getByAddress( rawIP );
         else
            addr = InetAddress.getByName( parent.hostName );
         System.out.println( "Inet address = " + addr );
         SocketAddress sockaddr =
               new InetSocketAddress( addr, parent.socketPort );
         // Create an unbound socket
         parent.client = new Socket();
         // This method will block no more than timeoutMs.
         // If the timeout occurs, SocketTimeoutException is thrown.
         parent.client.connect( sockaddr, parent.socketTimeOut );
         parent.socketOut =
               new BufferedWriter( new OutputStreamWriter(
               parent.client.getOutputStream() ) );
         parent.socketIn = new BufferedReader( new InputStreamReader(
               parent.client.getInputStream() ) );
         parent.localName = parent.localName +
               parent.client;
         System.out.println( "Parent socketOut = "+parent.socketOut);
         System.out.println( "Parent socketIn = "+parent.socketIn);
      catch ( UnknownHostException uhe )
         System.out.println( "Unknown Host - " + uhe.getMessage() );
      catch ( SocketTimeoutException ste )
         System.out.println( "Socket time out - " + ste.getMessage());
      catch ( IOException ioe )
         System.out.println( "IO exception - " + ioe.getMessage() );
      // Listen on socket for message from host - thread should block.
      parent.portConnected = true;
      while ( parent.portConnected )
         try
            String msg = parent.socketIn.readLine();
            System.out.println( "Message from Host: " + msg );
            System.out.println( "Message from Host: |" + msg + "|" );
            if( msg.length() > 2)parent.processMessage( msg );
         catch ( IOException ioe )
            System.out.println( "Exception creating server socket." );
      try
         System.out.println(
               "PortConnection - Closing socket and IO connections" );
         parent.socketIn.close();
         parent.socketOut.close();
         parent.client.close();
         parent.clockRunning = false;
         if( parent.heartBeating) heartBeat.interrupt();
      catch ( IOException ioex )
         System.out.println( "Exception closing socket." );
}

Your first problem is that you keep closing and recreating the ServerSocket. Do this once only in the lifetime of the server.
This is such a basic error that I haven't read the rest of the code. Before you go any further I suggest you read the Custom Networking trail of the Java Tutorial.

Socket communication very slow on Mac OS X 10.6

Hi everybody,
I'm using a socket based communication in an application and in Mac OS 10.5 everything works quick and flawless using XCode 3.1.4.
In Mac OS 10. 6, using XCode 3.2.4, I set the Mac OS X 10.6 SDK, I recompiled the app. but the responsiveness of the app is terrible slow. The GUI itself runs OK but any socket related action is painfully slow (sometimes connection timeout).
The socket communication is implemented using standard CFSocket classes.
Is this a XCode migration issue from 3.1 to 3.2 or a Mac OS 10.6 related one (I've seen lots of complains on networking issues)?
Thank you very much,
Dan

Thank you very much for the info but why it worked (and really fast) on 10.5. I also wonder why I didn't run into TCP_NODELAY problem there ? My TCP buffer size is 1K and I'm using the same testing environment.
Of course there is much more to it than some init parameters but still, what could be so different on 10.6 ? And I tried already the sysctl.conf TCP_NODELAY setting but no effect.
This is the code (briefly):
1. CONNECT
// Create signature from ip and port
struct sockaddr_in sin; /* TCP/UDP socket address structure. */
self->m_RemoteSocketSignature = (CFSocketSignature*)malloc(sizeof(CFSocketSignature));
self->m_RemoteSocketSignature->protocolFamily = PF_INET; /* IPv4 */
self->m_RemoteSocketSignature->socketType = SOCK_STREAM; /* Stream oriented. */
self->m_RemoteSocketSignature->protocol = IPPROTO_TCP; /* TCP */
memset( &sin, 0, sizeof( sin ) );
sin.sin_len= sizeof( sin );
sin.sin_family = AF_INET; /* Address is IPv4. Use PF_xxx for protocol
description, AF_xxx for address description. */
/* sin.port and sin.addr are in network( big endian ) byte order. */
sin.sin_port = CFSwapInt16HostToBig( port );
inet_aton( [address UTF8String], &sin.sin_addr ); /* inet_aton() gives back
network order addresses from strings. */
self->m_RemoteSocketSignature->address = CFDataCreate( NULL, (UInt8 *)&sin, sizeof( sin ) );
// Connect the Write & the Read streams to the socket
CFStreamCreatePairWithPeerSocketSignature (
kCFAllocatorDefault,
m_RemoteSocketSignature,
& m_ReadStream,
& m_WriteStream
if((m_ReadStream != NULL) && (m_WriteStream != NULL))
bOpenWrite = CFWriteStreamOpen (m_WriteStream);
bOpenRead = CFReadStreamOpen (m_ReadStream);
2. RECEIVE
CFIndex iTotalBytesRead = 0;
while (true == CFReadStreamHasBytesAvailable(m_ReadStream))
char buffer[1024];
CFIndex bufferLength = 1024;
CFIndex iBytesRead = CFReadStreamRead (
m_ReadStream,
buffer,
bufferLength
// Error ?
if(iBytesRead < 0)
return iBytesRead;
// EOS ?
if(iBytesRead == 0)
return iTotalBytesRead;
iTotalBytesRead += iBytesRead;
if(string != nil)
[string appendString:[NSString stringWithCString:buffer length:(unsigned)iBytesRead]];
3. SEND
CFIndex iBytesSent = CFWriteStreamWrite (
m_WriteStream,
buffer,
bufferLength
Thanks a lot for your help,
Dan

Socket communication via TCP-IP

Hi,
I am new to CF and would like to establish TCP-IP socket
communication with a remote server. How can I exchange XML messages
with a remote server / port via TCP-IP. Do I need to use the event
gateways of does CF offer another way of setting up socket
communication ?
Many thanks in advance !
John

Do I need to use the event gateways of does CF offer another way
of setting up socket communication ?
I would say, yes, use the socket gateway that ships with
Coldfusion. However, it has a functionality I cannot really
understand. If you are a client setting up a socket to connect to
the gateway, the gateway expects your code to have, beforehand, a
value for the variable
originatorID. Yet,
originatorID is a large, unique integer that the gateway
code generates when you connect. That seems to me to be a
chicken-and-egg dilemma.

Applet/servlet communication for byte transmission

Hello all !
I wrote an applet to transfer binary file from web servlet (running under Tomcat 5.5) to a client (it's a signed applet) but I have a problem of interpretation of byte during transmission.
the code of the servlet is :
 response.setContentType("application/octet-stream");
 ServletOutputStream sos = response.getOutputStream();
 FileInputStream fis = new FileInputStream(new File(
 "C:\\WINDOWS\\system32\\setup.bmp"));
 byte[] b = new byte[1024];
 int nbRead = 1;
 while (nbRead > 0) {
 nbRead = fis.read(b);
 System.out.println("octets lus = " + nbRead);
 sos.write(b, 0, nbRead-1);
 fis.close();
 sos.close();et le code de l'applet qui appelle cette servlet est :
 URL selicPortal = null;
 try {
 selicPortal = new URL(
 "http://localhost:8080/AppletTest/servlet/FileManipulation");
 } catch (MalformedURLException e) {
 e.printStackTrace();
 URLConnection selicConnection = null;
 try {
 selicConnection = selicPortal.openConnection();
 } catch (IOException e) {
 e.printStackTrace();
 selicConnection.setDoInput(true);
 selicConnection.setDoOutput(true);
 selicConnection.setUseCaches(false);
 selicConnection.setRequestProperty("Content-Type",
 "application/octet-stream");
 try {
 InputStream in = selicConnection.getInputStream();
 FileOutputStream fos = new FileOutputStream(new File(tempDir
 + "\\toto.bmp"));
 byte[] b = new byte[1024];
 int nbRead = in.read(b);
 while (nbRead > 0) {
 fos.write(b);
 in.close();
 fos.close();
 } catch (IOException ioe) {
 ioe.printStackTrace();
 }the file dowloaded is broken. it seems that bytes 01 00 or 00 01 are not correctly process.
Some ideas to help me please ?

hi,
have you solved this issue.. please post me the code since i m also doing the applet/servlet communication and can use your code as reference.
how to read the content placed in the urlConnection stream in the servlet
Below is my code in applet
public void upload(byte[] imageByte)
 URL uploadURL=null;
 try
 uploadURL=new URL("<url>");
 URLConnection urlConnection=uploadURL.openConnection();
 urlConnection.setDoInput(true);
 urlConnection.setDoOutput(true);
 urlConnection.setUseCaches(false);
 urlConnection.setRequestProperty("Content-type","application/octet-stream");
 urlConnection.setRequestProperty("Content-length",""+imageByte.length);
 OutputStream outStream=urlConnection.getOutputStream();
 outStream.write(imageByte);
 outStream.close();
 catch(MalformedURLException ex)
 catch(IOException ex)
How can i read the byte sent on the outstream (in above code) in the servlet.
Thanks,
Mclaren

Java WD and Socket Communication

Hi,
Is it possible to use Java Socket Communication with Java Web Dynpro. Or if not what is the best approach to have a Java Socket program integrated with a Web Dynpro Communication.
Basically, I have an application which provides API for communication via Java Sockets.And this needs to be integrated in our SAP application.
Thanks,
CD

Hi,
You are currently using JCO to "Connect to a Remote System" - JCO will connect to a back-end with the main purpose of "executing BAPI's" in it.
When you move to WebDynpro, you have what SAP calls Adaptive RFC Model - this will create a "Model Entity" in you WD Project that will do the same thing your JCO does.
Assume your JCO now calls "BAPI_GET_FLIGHTS", to return the Flights that are currently available - In your newly create WDP Project, you will manually specify what back-end you wanna use when "Importing" and you will tell also the BAPI name. WDP will generate the class structure that you need in order to execute that function.
JCO is what SAP created to execute BAPI's. JCO can be used by any "Java" like application that needs to connect to the back-end. But when you move to WDP, you don't need to use this anymore - You will use WDP Models.
Youi will still need your JCO Destinations created in the Application Server, so behind the scenes WDP creates a "layer" so you don't need to code the JCO calls manually.
Regards,
Daniel

Does XI support Socket communication?

Hi,
This question came from our customers and consultants.
I saw the definition of socket in Wikipedia that it is somehow based on TCP, UDP. So far as I know, XI does not "support" TCP/IP. Does this mean XI does not support Socket either? Or this could be covered in the adapters of XI?
If XI does not support this, do you have any experience of a solution to socket communication?
Thanks in advance!
best regards
Jing

Hi,
sorry for the late reply.
I understand you that PI does not quite meet healthcare specific requirements.
Regrading medical equipment with PI, I am not familiar with that part.
But I have good news regarding HL7 protocol with PI. In the meantime we (SAP) have a service solution of HL7 adapter for PI, that supports HL7 communications based on HL7 message format/protocol.
Details please see this blog from Vijendra: http://scn.sap.com/docs/DOC-3891
hope this helps you.
Regards
Jing

Is there a good advanced review on applet-servlet communication

I am working on a web application and unfortunately experiencing a lot of trouble trying to use an applet as front end which interacts with a couple of servlets running on Tomcat. I need to get data from one servlet and send data to another.
There is a lot of messages posted in this and other forums about how to do this, but none of them got a response pointing to a useful advanced reference on this subject. I have reviewed some of the references given, but couldn't find a thorough detailed advanced reference on applet-servlet communication. For this I mean an exhaustive explanation of the mechanism of communication and when and when is neccesary to use each of the multiple configuration possibilities regarding content-type, message-length, request-method, connection settings, and so on.
Would anybody be so kind to show me the right direction? As I read the (literally) hundreds of messages posted on this topic, I see this info as widely useful. Most of the topic tracks ends on void or with painful no-way sentences, and maybe many people is avoiding Java technology on web application because of this problem (development delays can abort a project).

This sample chapter in Java developers' guide to Servlets and Jsp focuses on Applet-Servlet communication, is a pretty good one, and is free :
http://www.javaranch.com/bunkhouse/samps/2809ch12.pdf
As to an exhaustive & complete guide that covers absolutely everything, I may be wrong but I doubt you'll find anything like that...unless there is a book somewhere dedicated to the subject.

Applet-servlet communication, object serialization, problem

hi,
I encountered a problem with tomcat 5.5. Grazing the whole web i didn't find any solution (some guys are having the same problem but they also got no useful hint up to now). The problem is as follows:
I try to build an applet-servlet communication using serialized objects. In my test scenario i write a serialized standard java object (e.g. a String object) onto the ObjectOutputStream of the applet/test-application (it doesn't matters wheter to use the first or the latter one for test cases) and the doPost method of the servlet reads the object from the ObjectInputStream. That works fine. But if i use customized objects (which should also work fine) the same code produces an classnotfound exception. When i try to read and cast the object:
TestMessage e = (TestMessage)objin.readObject();
java.lang.ClassNotFoundException: TestMessage
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1359)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205)
    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
...That seems strange to me, because if i instantiate an object of the same customized class (TestMessage) in the servlet code, the webappclassloader doesn't have any problems loading and handling the class and the code works fine!
The class is located in the web-inf/classes directory of the application. I've already tried to put the class (with and without the package structure) into the common/classes and server/classes directory, but the exception stays the same (I've also tried to build a jar and put it in the appropriate lib directories).
I've also tried to catch a Throwable object in order to get information on the cause. But i get a "null" value (the docu says, that this will may be caused by an unknown error).
I've also inspected the log files intensively. But they gave me no hint. Until now I've spend a lot of time on searching and messing around but i always get this classnotfound exception.
I hope this is the right place to post this problem and i hope that there is anyone out there who can give me some hint on solving this problem.
Kindly regards,
Daniel

hi, thanks for the reply,
all my classes are in the web-inf/classes of the web-app and have an appropriate package structure. thus the TestMessage class is inside a package.
i tried some names for the testclass but it didn't matter. the exception stays the same. I also tried to put the jar in the common/lib but the problem stays.
Well the problem with loaded classes: As i mentioned in the post above i can instantiate an object of TestMessage in the code without any problems (so the classloader of my webapp should know the class!!)
only when reading from the objectinputstream the classloader doesn't seem to know the class?? maybe theres a parent classloader resposible for that and doesn't know the class?
strange behaviour...
p.s. sending the same object from the servlet to the client works well
regards
daniel
Message was edited by:
theazazel

Re:Applet socket communication

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