Newline with output stream
How do I create a new line with a DataOutputStream (created from a fileOutputStream) in ASCII format
(so that you can also see it as a new line in notepad)
String eol = System.getProperty( "line.separator" );
Similar Messages
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Reading native process standard output stream with ProcessBuilder
Hi,
I'd like to launch an native process (windows application) which writes on standard output during its running.
I'd like to view my application output on a JTextArea on my Java frame (Swing). But I do get all process output
on text area only when the process is finished (it takes about 20 seconds to complete). My external process is
launched by using a ProcessBuilder object.
Here is my code snippet with overridden doInBackground() and process() methods of ProcessBuilder class:
@Override
public String doInBackground() {
jbUpgrade.setEnabled(false);
ProcessBuilder pb = new ProcessBuilder();
paramFileName = jtfParameter.getText();
command = "upgrade";
try {
if (!(paramFileName.equals(""))) {
pb.command(command, jtfRBF.getText(), jtfBaseAddress.getText(), "-param", paramFileName);
} else {
pb.command(command, jtfRBF.getText(), jtfBaseAddress.getText());
pb.directory(new File("."));
pb.redirectErrorStream(false);
p = pb.start();
try {
InputStream is = p.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line;
jtaOutput.setText("");
while ((line = br.readLine()) != null) {
publish(line);
} catch (IOException ex) {
Logger.getLogger(CVUpgradeFrame.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(CVUpgradeFrame.class.getName()).log(Level.SEVERE, null, ex);
jtaOutput.setText("");
jtaOutput.setLineWrap(true);
jtaOutput.append("Cannot execute requested commmad:\n" + pb.command());
jtaOutput.append("\n");
jtaOutput.setLineWrap(false);
return "done";
@Override
protected void process(List<String> line) {
jtaOutput.setLineWrap(true);
Iterator<String> it = line.iterator();
while (it.hasNext()) {
jtaOutput.append(it.next() + newline);
jtaOutput.repaint();
//Make sure the new text is visible, even if there
//was a selection in the text area.
jtaOutput.setCaretPosition(jtaOutput.getDocument().getLength());
How can I get my process output stream updated while it is running and not only when finished?
Thanks,
jluke1) Read the 4 sections of http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html and implement the recommendations. Although it is concerned with Runtime.exec() the recommendations still apply to Process generated by ProcessBuilder.
2) Read about concurrency in Swing - http://java.sun.com/docs/books/tutorial/uiswing/concurrency/ .
3) Use SwingUtilities.invokeLater() to update your GUI. -
MultiThreading with Input and Output Streams
Hi,
I have a problem and I think it's because I'm not coding correctly. Please help me if you can understand what I'm doing wrong.
I have a server that spawns a separate thread to go off and collect data from a serial port. It also waits to accept connections from any client and if a connection is made it will send that data to the clients connected.
There is data constantly coming in through the serial port. It is output through a DataOutputStream so when the thread is created in the server, I pipe it into a DataInputStream. I do does because I want the server to then read in the data from the inputstream and then send it out to all my clients.
So far, the way I have it set up seems to do this. But my problem occurs when I try to close a client connection. Instead of removing the socket connection it gives me an error that it can't send data to the client, but it shouldn't be sending data to the client because I just closed it. I realize this is probably because I'm still constantly receiving data from my inputstream and the connection was closed so it can't send that data to the client. I know I need to either close the stream or close my socket but I don't know where this needs to be done. I'm stuck on the correct way to fix this.
My second problem is the initial connection made to receive data from the inputstream. This is probably because I'm not very familiar with how input/output streams work. But instead of just sending the client the current data being received in real time, it'll send all the data that's buffered in the inputstream. I don't want all the data that's been collecting to go to that first client. I only want the recent data that is coming through while the client is connected. Does this make sense? Because after I make a second client connection I don't have this problem because the InputStream is no longer buffered up. Should I be using something else besides the DataInputStream?
I feel like I'm going about this the wrong way. Please advise. I'm shy about showing the code but I've included the bulk of it here in hopes that someone will see what I'm doing wrong. The only part that's left out is the thread that reads from the serial port. I don't seem to have any problems with that thread.
Thanks,
kim
===
import java.io.*;
import java.net.*;
import javax.comm.*;
import java.util.*;
// DataServer waits for a client connection
class DataServer
static final int PORT = 7;
// The ServerSocket to use for accepting new connections
private ServerSocket ss;
// A mapping from sockets to DataOutputStreams. This will
// help us avoid from having to create a DataOutputStream each time
// we want to write to a stream.
private Hashtable outputStreams = new Hashtable();
// The inputstream that will receive serial port data through a
// piped inputstream
public DataInputStream datalogger;
// Constructor and while-accept loop all in one.
public DataServer() throws IOException
try {
// Creating pipe to convert the outputstream from the
// RS232 Thread to an inputstream for the server to read
PipedOutputStream pout = new PipedOutputStream();
PipedInputStream pin = new PipedInputStream(pout);
// The inputstream that will receive data from the RS232Thread
datalogger = new DataInputStream(pin);
// Spawn the thread that will read data through from
// the TINI serial port
new RS232Thread( pout ).start();
// Begin listening for connections and send data
listen();
} catch (IOException ioe) {
System.out.println("Error >> DataServer::DataServer()");
System.out.println(ioe.getMessage());
ioe.printStackTrace();
} finally {
try {
System.out.println( "Closing >> DataServer::DataServer()" );
datalogger.close();
} catch (IOException i ) {
System.out.println( "Error2 >> DataServer::DataServer()" );
System.out.println(i); }
private void listen() throws IOException
// Create the ServerSocket
ss = new ServerSocket( PORT );
// Inform that the server is ready to go
System.out.println( "Listening on " + ss );
// Keep accepting connections forever
while (true) {
// Grab the next incoming connection
Socket s = ss.accept();
// Inform that connection is made
System.out.println( "Connection from " + s );
// Create a DataOutputStream for writing data to the
// other side
DataOutputStream dout = new DataOutputStream( s.getOutputStream() );
// Save this stream so we don't need to make it again
outputStreams.put( s, dout );
// Create a new thread for this connection, and then foret
// about it
new ServerThread( this, s );
// Get an enumeration of all the OutputStreams, one for each client
// connected to the server
Enumeration getOutputStreams() {
return outputStreams.elements();
// Send a message to all clients (utility routine)
void sendToAll( byte[] b ) {
// synchronize on this because another thread might be
// calling removeConnection() and this would screw things up
// while it walks through the list
synchronized( outputStreams ) {
// For each client...
for (Enumeration e = getOutputStreams(); e.hasMoreElements();) {
// ... get the output stream ...
DataOutputStream dout = (DataOutputStream)e.nextElement();
// ... and send the message
try {
dout.write( b );
} catch(IOException ie) {
System.out.println( "Error >> ServerThread::sendToAll()" );
System.out.println( ie );
// remove a socket, and it's corresponding output stream, from the
// list. This is usually called by a connection thread that has
// discovered that the connection to the client is dead.
void removeConnection( Socket s ) {
// Synchronize so it doesn't mess up sendToAll() while it walks
// down the list of all output streams
synchronized( outputStreams ) {
// Inform about removal
System.out.println( "Removing connection to " + s );
// Remove if from our hastable/list
outputStreams.remove( s );
// Make sure it's closed
try {
s.close();
} catch( IOException ie ) {
System.out.println( "Error closing " + s );
ie.printStackTrace();
// main - Opens a server socket and spins off a new thread each time
// a new client connection is accepted on this socket.
public static void main(String[] args) throws Exception
System.out.println("Starting DataServer version 1.0 ...");
try
new DataServer();
catch (IOException ioe)
System.out.println( "Error >> DataServer::main()" );
System.out.println(ioe.getMessage());
ioe.printStackTrace();
class ServerThread extends Thread
//The Server that spawned this thread
private DataServer server;
// The Socket connected to the client
private Socket socket;
//Constructor
public ServerThread( DataServer server, Socket socket )
// save the parameters
this.server = server;
this.socket = socket;
// Start up the thread
start();
// This runs in a separate thread when start() is called in the
// constructor
public void run() {
try {
// The inputstream receiving data from the global inputstream
// that is piped to the RS232 Thread
// ???? is this where i'm messing up ???
DataInputStream in = new DataInputStream( server.datalogger );
int num = 0;
byte[] d = new byte[1];
// read from the inputstream over and over, forever ...
while( ( num = in.read(d) ) > 0 ) {
// ... and have the server send it to all clients
server.sendToAll( d );
} catch (IOException ioe) {
System.out.println( "Error >> ServerThread::run()" );
System.out.println(ioe.getMessage());
ioe.printStackTrace();
} finally {
// The connection is closed for one reason or another,
// so have the server dealing with it
System.out.println( "Closing" );
server.removeConnection( socket );A couple of things to note...
First, you are looping infinitely in your server's constructor. Since the constructor is never completing, your server object is never completely constructed - this may cause indeterminate behaviour when you pass a reference to the server to another thread.
Second, I would recommend fixing your issues by modifying your design somewhat. The design I would recommend (read: The design I would use) is:
A server object, with a public listen method. The constructor spawns a thread to constantly read from the serial port and forward the data read back to the server, via a multicast (sendToAll) method.
The listen method sets up a server socket to accept connections, and in a loop opens client sockets and stores them in a set.
The multicast method iterates through the list of open client sockets, and for each in turn confirms that it is still open. If open, send the data down the socket's output stream; if closed, remove the socket from the set.
Note that this design includes only two threads - the main thread listens for and accepts new socket connections, while the extra thread collects data from the serial port, multicasts it to all of the open sockets, and removes all of the closed sockets. If you require to perform any other communication with the sockets, it may be necessary to create a thread for those sockets, to facilitate reading from their input streams, but in the given design, this is not necessary.
I hope this helps,
-Troy -
Getting the Output Stream of a Process without exec()ing it first.
Hi there,
I am writing a java application which needs to open another application "gnuplot". Now my operating system is windows and I open pgnuplot .
Also I want to send input to the above gnuplot (say plot sin(x) ) via the outputStream. The following is what I do :-
String gnuplot_cmd = "plot sin(x)\n" ;
Process p = Runtime.getRuntime().exec("C:/gnuplot/gnuplot4/bin/pgnuplot.exe");
PrintWriter gp = new PrintWriter(p.getOutputStream());
gp.print(gnuplot_cmd);
gp.close();
But the above doesn't work fully , in that only the blank wgnuplot terminal window pops up however I am unable to direct input to the gnuplot application.
The reason being that , pgnuplot checks for
its stdin being redirected the moment it's started. If, at that time,
the "PrintWriter" is not yet connected to the OutputStream of the
process, that check will fail, and pgnuplot will revert to just executing
wgnuplot, without any command line redirection.
I am facing a problem of how to attach a OutputStream to the process, without getting exec()ing the process.
Is there anyway at all, i can get a process without starting it, so that I can attach an output Stream to it before it gets executed?
I am open to work arounds, anything that will automate the process of writing to the gnuplot terminal.
thanks!
nandita.The reason being that , pgnuplot checks for
its stdin being redirected the moment it's started.
If, at that time,
the "PrintWriter" is not yet connected to the
OutputStream of the
process, that check will fail, and pgnuplot will
revert to just executing
wgnuplot, without any command line redirection. I'm not convinced this analysis is correct. gnuplot doesn't need to know that there's a PrintWriter there, and it probably can't know. It just needs to know whether its standard input is coming from console or not. The Java library code that can invoke processes probably handles the redirect right away, and that's why there's the OutputStream available even before you create the PrintWriter.
exec can be tricky. I think the problem may be that you're not dealing with standard output or standard error. Read this:
When Runtime Exec Won't
If that still doesn't help, there may be options to gnuplot to tell it exactly where its input is coming from. -
Error flushing the output stream in Sun One server
Hi All,
I was running my servlet code in iPlanet 6.0 version and it was working fine. I upgraded my web server to new Sun One server (Oracle-iPlanet-Web-Server-7.0.9). With the new web server almost 90% of my application works fine, but there is a features in my application to download an Excel sheet by clicking a button. This feature is failing in new Sun One web server.
Below are my piece of code and the error log I m getting. Can anyone tell me how I can fix this error, I mean is there any web server specific change or configuration parameter need to be set.
Please ask for any information regarding my server configuration settings if needed for finding a solution for this
Code:
byte abyte0[] = new byte[1024];
BufferedInputStream bufferedinputstream=null;
BufferedOutputStream bufferedoutputstream=null;
java.io.InputStream inputstream = httpurlconnection.getInputStream();
bufferedinputstream = new BufferedInputStream(inputstream);
bufferedoutputstream = new BufferedOutputStream(httpservletresponse.getOutputStream());
int j;
long byteCount=0;
while((j = bufferedinputstream.read(abyte0, 0, 1024)) != -1)
byteCount=byteCount+j;
if(logger != null && logger.traceOn())
logger.log("total"+byteCount);
logger.log("Read bytes:"+j);
bufferedoutputstream.write(abyte0, 0, j);
if(logger != null && logger.traceOn())
logger.log("Wrote bytes:"+j);
bufferedoutputstream.flush(); // <<<<<< ERROR POINT >>>>>>
Error Log :
ClientAbortException: java.io.IOException: WEB8004: Error flushing the output stream
at org.apache.coyote.tomcat5.OutputBuffer.doFlush(OutputBuffer.java:343)
at org.apache.coyote.tomcat5.OutputBuffer.flush(OutputBuffer.java:313)
at org.apache.coyote.tomcat5.CoyoteOutputStream.flush(CoyoteOutputStream.java:147)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:124)
at com.reuters.bdec.as.ASRequestHandler.processResponse(ASRequestHandler.java:285)
at com.reuters.bdec.as.ASRequestHandler.initiateGetRequest(ASRequestHandler.java:89)
at com.reuters.bdec.as.ASRequestHandler.proceedToDestination(ASRequestHandler.java:220)
at com.reuters.bdec.as.ASExtension.authorisationCheck(ASExtension.java:84)
at com.reuters.bdec.as.ASExtension.doGet(ASExtension.java:114)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:794)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:915)
at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:398)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:277)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:255)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:586)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:556)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:187)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:586)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:556)
at com.sun.webserver.connector.nsapi.NSAPIProcessor.service(NSAPIProcessor.java:160)
Caused by: java.io.IOException: WEB8004: Error flushing the output stream
at com.sun.webserver.connector.nsapi.NSAPIProcessor.action(NSAPIProcessor.java:243)
at org.apache.coyote.Response.action(Response.java:197)
at org.apache.coyote.tomcat5.OutputBuffer.doFlush(OutputBuffer.java:339)
... 20 moreDon't flush it yourself. The servlet container will automatically flush for you once its send buffer is full. You can change the size of the send buffer though.
-
Questions about input/output streams
In the following tutorial:
http://chortle.ccsu.ctstateu.edu/CS151/Notes/chap85/ch85_10.html
It mentions that some methods, such as write(), writeByte(), writeBytes(), and writeChar(), return the low eight bits of the argument to the output stream. I am a little unsure of what exactly that means, might somebody be able to clarify for me?
In addition, I've been encountering the flush() method in some of the byte- and character-streaming objects that deal with buffers. What exactly is the flush() method's purpose, and when might it be used? Thank you.flush pushes the data out of the buffer. the write methods write to the buffer, when the buffer is full, it flushes itself (usually), or it could block the write methods (in theory). flush just lets you make sure that it's flushed.
I'm not sure there's any reason to worry about high and low bytes in Java most of the time. I suppose, like anything, there's times you need to, but I can't think of any offhand. -
Exception writing binary data to the output stream to client -Broken pipe
Hi,
I am trying to use the drag & drop feature using Contributor mode of Webcenter sites. Single Image Page Attribute is working properly where as Multiple Image Page Attribute throws the following error:
[ERROR] [.kernel.Default (self-tuning)'] [logging.cs.satellite.request] Exception writing binary data to the output stream to client 10.191.117.106
java.net.SocketException: Broken pipe
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:92)
at java.net.SocketOutputStream.write(SocketOutputStream.java:136)
at weblogic.servlet.internal.ChunkOutput.writeChunkTransfer(ChunkOutput.java:568)
at weblogic.servlet.internal.ChunkOutput.writeChunks(ChunkOutput.java:539)
at weblogic.servlet.internal.ChunkOutput.flush(ChunkOutput.java:427)
at weblogic.servlet.internal.ChunkOutput$2.checkForFlush(ChunkOutput.java:648)
at weblogic.servlet.internal.ChunkOutput.write(ChunkOutput.java:333)
at weblogic.servlet.internal.ChunkOutputWrapper.write(ChunkOutputWrapper.java:148)
at weblogic.servlet.internal.ServletOutputStreamImpl.write(ServletOutputStreamImpl.java:148)
at COM.FutureTense.Servlet.ServletRequest$OutputOutputStream.write(ServletRequest.java:80)
at COM.FutureTense.Servlet.ServletRequest.write(ServletRequest.java:1633)
at com.openmarket.Satellite.RequestContext.write(RequestContext.java:1123)
at com.openmarket.Satellite.BytePiece.stream(DataPiece.java:253)
at com.openmarket.Satellite.CacheObjectImpl.stream(CacheObjectImpl.java:651)
at com.openmarket.Satellite.Http11Responder.respondForWrapper(Http11Responder.java:142)
at com.openmarket.Satellite.WrapperAwareResponder.respond(WrapperAwareResponder.java:36)
at com.openmarket.Satellite.SatelliteServer.execute(SatelliteServer.java:85)
at com.openmarket.Satellite.servlet.BaseServlet.doGet(BaseServlet.java:118)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227)
at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)
at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:301)
at weblogic.servlet.internal.TailFilter.doFilter(TailFilter.java:26)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at com.fatwire.wem.sso.cas.filter.CASFilter.doFilter(CASFilter.java:557)
at com.fatwire.wem.sso.SSOFilter.doFilter(SSOFilter.java:51)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.wrapRun(WebAppServletContext.java:3730)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3696)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:120)
at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2273)
at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2179)
at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1490)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:256)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:221)
Thanks
KarthiKThank u very much,
FileOutputStream opGif = new FileOutputStream(destFile, false);
I have changed above line with the following line:
PrintWriter opGif = new PrintWriter ( new FileWriter(destFile, false));
and now this code is working very fine.
Thanks once again... -
Facing error in creating ObjectInput/output stream socket
hi I am Jatandar and i am implemeint client server program which will be using object Input/Output stream to pass data through sockets . The problem is the i m getting error when the cleint connects to the server here is the server and client code , YOur help will be appreciated
Inventory class with serializable has been implemented
public class Client
public static void main( String [] args )//throws IOException
Inventory invt[];
try
Socket serv = new Socket( "localhost", 8000 );
// connect to server at port 8000
ObjectInputStream ois ;
ois= new ObjectInputStream(serv.getInputStream());
invt=(Inventory[]) ois.readObject() ;
System.out.println(invt[0]);
catch(IOException e )
System.out.println(" no server Found \n");
catch(Exception e)
System.out.println(e);
public class A3Server
public static void main(String arg[] ) throws IOException
//create a Server Socet
ServerSocket ss= new ServerSocket(8000) ;
ObjectOutputStream oos;
//create a clent Socker that will listen for connection
//listen for the connection from client
BufferedReader br=null;
FileReader fr=null;
LinkedList ll=new LinkedList();
StringTokenizer stkr;
int i=0;
Inventory inv=new Inventory();
Inventory invt[];
String t[]=new String[5];
boolean choice=true;
String temp="",temp2;
// i am reading a text which contain data
//that data is stored in invt []
//that array is transfered to clien t when it is connected
Socket toClient= ss.accept();
oos = new ObjectOutputStream(toClient.getOutputStream());
oos.writeObject(invt );
oos.close();
}// end of main fucniton
}//end of Server class
DETAIL OF ERROR
error in natived socket write methodhi I am Jatandar and i am implemeint client server program which will be using object Input/Output stream to pass data through sockets . The problem is the i m getting error when the cleint connects to the server here is the server and client code , YOur help will be appreciated
Inventory class with serializable has been implemented
public class Client
public static void main( String [] args )//throws IOException
Inventory invt[];
try
Socket serv = new Socket( "localhost", 8000 );
// connect to server at port 8000
ObjectInputStream ois ;
ois= new ObjectInputStream(serv.getInputStream());
invt=(Inventory[]) ois.readObject() ;
System.out.println(invt[0]);
catch(IOException e )
System.out.println(" no server Found \n");
catch(Exception e)
System.out.println(e);
public class A3Server
public static void main(String arg[] ) throws IOException
//create a Server Socet
ServerSocket ss= new ServerSocket(8000) ;
ObjectOutputStream oos;
//create a clent Socker that will listen for connection
//listen for the connection from client
BufferedReader br=null;
FileReader fr=null;
LinkedList ll=new LinkedList();
StringTokenizer stkr;
int i=0;
Inventory inv=new Inventory();
Inventory invt[];
String t[]=new String[5];
boolean choice=true;
String temp="",temp2;
// i am reading a text which contain data
//that data is stored in invt []
//that array is transfered to clien t when it is connected
Socket toClient= ss.accept();
oos = new ObjectOutputStream(toClient.getOutputStream());
oos.writeObject(invt );
oos.close();
}// end of main fucniton
}//end of Server class
DETAIL OF ERROR
error in natived socket write method -
I have maybe simple question, but I can`t really understand how to figure out this problem.
I have 2 applications(one on mobile phone J2ME, one on computer J2SE). They commuinicate with Input and Output Streams. Everything is ok, but all communication is in sequence, for example,
from mobile phone:
out.writeUTF("GETIMAGE")
getImage();
form computer:
reply = in.readUTF();
if(reply.equals("GETIMAGE")) sendimage()
But I need to include one simple thing in my applications - when phone rings there is function in MIDlet - pauseApp() and i need to send some signal to Computer when it happens. But how can i catch this signal in J2SE, because mayble phone rings when computer is sending byte array? and then suddnely it receives command "RINGING"....?
Please explain how to correcly solve such problem?
Thanks,
ErvinsEh?
TCP/IP is not a multiplexed protocol. And why would you need threads or polling to decipher a record-oriented input stream?
Just send your images in packets with a type byte (1=command, 2=image, &c) and a packet length word. At the receiver:
int type = dataInputStream.read();
int length = dataInputStream.readInt();
byte[] buffer = new byte[length];
int count, read = 0;
while ((count = dataInputStream.read(buffer,count,buffer.length)) > 0)
read += count;
// At this point we either have:
// type == -1 || count = -1 => EOF
// or count > 0, type >= 0, and buffer contains the entire packet.
switch (type)
case -1:
// EOF, not shown
break;
case COMMAND: // assuming a manifest constant somewhere
// process incoming command
break;
case IMAGE:
// process or continue to process incoming image
break;
}No threads, no polling, and nuthin' up my sleeve.
Modulo bugs. -
PDF Document as an Output Stream.
Hi,
I have created a PDFwriter class that easily creates and writes a PDF document stream to a fileout stream.I am using JSP to do the same.
What i want to do now is directly send the stream to an output stream instead of a fileoutput stream. Question is which one??
How do i pass it to response obj, (response.setOutputStream(System.out) does not work)
I am Pasting some code so that you can understand what i mean( >> means next step)
Document document = new Document(PageSize.A4.rotate(), 10, 10, 30, 20); >>
File file = new File("C:\\ePro\\PDFGenerator\\Report.pdf"); >> document.open();
Table table = new Table(9); >> table.setPadding(0); >> table.setSpacing(1); >>
table.addCell(new cell ("Any String",fontF); >> document.add(table); >> document.close(); >>
PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(file));
The above code creates a PDF file on my disk which i can then redirect. Eg
response.setContentType("application/pdf");
response.sendRedirect("Report.pdf");
What i want now is to replace the constructor for PDFWriter with a different Output stream and directly write it to browser.
Please help as i am stuck for quite some time now....byte[] pdfContent = PDFProcessor.getPDFStream(roleID,report,Integer.parseInt(languageID));
response.setContentType("application/pdf");
ServletOutputStream out = response.getOutputStream();
System.out.println("Writing PDF");
out.write(pdfContent);
out.flush(); -
Problem with output string to command
hey i have no idea why this aint working
its a simple output string to command.
what it is supposed to do is make a new directory given by the input string
e.g. mkdir /home/luke/dep
thanks for the help
//methods input save files
saveFile = JOptionPane.showInputDialog("Save Files To : ");
//method command for saving files
//Stream to write file
FileOutputStream fout;
try { Process myProcess = Runtime.getRuntime().exec("mkdir" + saveFile );
InputStreamReader myIStreamReader = new InputStreamReader(myProcess.getInputStream());
fout = new FileOutputStream ("file.txt");
while ((ch = myIStreamReader.read()) != -1) { new PrintStream(fout).print((char)ch); } }
catch (IOException anIOException) { System.out.println(anIOException); }What you fail to understand is that "aint working" and "Problem with output string to command" tells us absolutely squat about what your problem is. This is the same as saying to the doctor "I'm sick" and expecting him to cure you. As mentioned by Enceph you need to provide details. Do you get error messages? If so post the entire error and indicate the line of code it occurs on. Do you get incorrect output? Then post what output you get, what output you expect. The more effort you put into your question the more effort others will put in their replies. So until you can manage to execute a little common sense then the only responses you will get will be flames. Now is your tiny little brain able to comprehend that?
-
Hi there,
I would like to have the output stream coming from the server to the client displayed on a JTextArea. However, because the coming file is a text document that had its file name passed as a local variable in the main method header with String a[ ], I am having difficulty setting this as the area text because of the incompatible types. This text prints on my command prompt window but I cannot figure out how to get this stream into the JTextArea. This is my code. The objective is to ask a file from the server and have the server send this file to the client so the client can then make changes and save.
import java.io.*;
import java.net.*;
import javax.swing.JFrame;
import javax.swing.JTextArea;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JScrollPane;
import javax.swing.JButton;
import javax.swing.Box;
import java.io.FileReader;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Scanner;
import java.util.Formatter;
public class Client extends JFrame{
public static JTextArea enterArea1;
public static JTextArea enterArea2;
public JButton change;
public JButton save;
public Client()
super ("Client to Server");
Box box = Box.createHorizontalBox();
enterArea1 = new JTextArea(10, 15);
enterArea1.setEditable (true);
box.add (new JScrollPane (enterArea1));
change = new JButton("Make Changes");
box.add(change);
change.addActionListener(
new ActionListener()
public void actionPerformed(ActionEvent event)
Scanner console = new Scanner (System.in);
System.out.print ("Input File: ");
String inputFileName = console.next ();
System.out.print ("Enter the text that you want to change");
String inputText1 = console.next ();
System.out.print ( "Output File: ");
String outputFileName = console.next();
try
FileReader reader = new FileReader (inputFileName);
Scanner in = new Scanner (reader);
PrintWriter out = new PrintWriter (outputFileName);
String line1 = in.nextLine();
out.println( " " + inputText1 );
out.close();
catch (IOException exception)
System.out.println ("Error processing file: " + exception);
save = new JButton("Save to File");
box.add(save);
save.addActionListener(
new ActionListener()
public void actionPerformed(ActionEvent event)
enterArea2.setText (enterArea1.getSelectedText());
enterArea2 = new JTextArea (10, 15);
enterArea2.setEditable (false);
box.add (new JScrollPane (enterArea2));
add (box);
public static void main(String a[]) throws IOException {
Socket sock;
BufferedReader dis;
PrintWriter dat;
Client sendServer = new Client();
sendServer.setSize (500, 200);
sendServer.setVisible(true);
sendServer.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
sock = new Socket("127.0.0.1",4444);
dis = new BufferedReader( new InputStreamReader(sock.getInputStream()) );
dat = new PrintWriter( sock.getOutputStream() );
dat.println(a[0]);
dat.flush();
enterArea1.setText(a[0]);
PrintStream os = new PrintStream (new FileOutputStream ("out.txt"));
String fromServer = dis.readLine();
while (fromServer != null )
System.out.println(fromServer);
os.println(fromServer);
fromServer = dis.readLine();
sock.close();
}I believe that the logic is to append the text to the JTextArea with something along the lines of this, but since String a[0] is passed in my void method, it is not accepted as a string anymore. The question then becomes how to create a variable that is referenced to the output text on the command window so that this variable can be used to append the same text to the JTextArea. I will appreciate any comments. Right now, it sees the String text as null.
String text = dat.println(a[0]);
dat.flush();
enterArea1.append(text]); -
Java Sockets and Output Streams
Hi All,
I am beginning sockets programming and I have a problem. If there is a server listening in the background for incoming connections and say for example 4 client programs programs which we shall call client1...client4 connect. How best can I capture the output streams associated with these newly created sockets so that the server can send back isome nformation to say clients1 and client4 only which is not seen by clients 2 and 3. Similarly I would like the server to send some infor to clients 2 and 3 only which is not seen by client1 and client 4.
Currently I have the server listening part as shown below, but not too sure how to add DISTINCT output streams for 1 and 4 on one hand and 2 and 3 on the other.
Thanks:
// bind socket to a port number
ServerSocket serverSocket = new ServerSocket(portNo);
// create socket to listen to client connection
while (true) {
//listen to an incoming connection
System.out.println("chatroom server waiting for incoming connections");
Socket incomingSocket = serverSocket.accept();
//launch new thread to take care of new connection
chatRoomThread chatThread = new chatRoomThread(incomingSocket);
chatThread.start();
//go back and wait for next connection
Please help.
Thanks,
BleakHouseofHunger wrote:
yes thats exactly the way I have my in and out streams, in the run method, but that doesn't help me in filtering traffic, in other words I am saying 2 clients, client1 and client4 for example should share a common in and out stream so that they will see eact other's messages... makes sense.....?No, doesn't make sense. That's the wrong design. Each socket should have its own input and output stream (yes, I know, that's been said several times before). If messages going to client1 should also be sent to client4, then whatever writes the messages to client1's output stream must also write them to client4's output stream. Trying to make those two output streams actually be the same output stream is the wrong way to do that. Just have the controller send the messages to whoever is supposed to get them. -
Hello every body..
I have aproject that use the java applet to transmit a vedio and audio over the internet network to do a video conference application with other applet at another computer at the network..
I want to support the application so that the user that enter the conference can select the bandwidth of the internet he/she use and then accordin to choice i control the quality of the stream transmitted..
So i want any one can help me with any way can be used to reduce the quality( or resolution) of the output stream so the user can be comfortable with the output..
please any one can help me reply to me as fast as can..
I there is no method can be used also reply and say this..
Thanks...Hi,
For audio use GSM codec. It just takes 12kbps of your bandwidth.
For video, if you need "ok" quality with low bandwidth, use H.263 codec and for good quality, but higher bandwidth use JPEG codec. below are complete functions on how to reduce qualities for both codecs (or at least try to). But before you have to create a video Processor (see AVTransmit3.java and AVReceive3.java examples on the net).
private void setReducedJPEGQuality(Processor videoProcessor) {
Control cs[] = videoProcessor.getControls();
QualityControl qc = null;
VideoFormat jpegFmt = new VideoFormat(VideoFormat.JPEG);
// Loop through the controls to find the Quality control for
// the JPEG encoder.
for (int i = 0; i < cs.length; i++) {
if (cs[i] instanceof QualityControl && cs[i] instanceof Owned) {
Object owner = ((Owned)cs).getOwner();
// Check to see if the owner is a Codec.
// Then check for the output format.
if (owner instanceof Codec) {
Format fmts[] = ((Codec)owner).getSupportedOutputFormats(null);
for (int j = 0; j < fmts.length; j++) {
if (fmts[j].matches(jpegFmt)) {
qc = (QualityControl)cs[i];
qc.setQuality(0.5f);
break;
if (qc != null) {
break;
This will reduce your JPEG bandwith to an average of 150kbps, with still a good quality.
private void setReducedH263Quality(Processor videoProcessor) {
Control cs[] = videoProcessor.getControls();
QualityControl qc = null;
BitRateControl brc = null;
FrameRateControl frc = null;
boolean done = false;
//try with bit rate first
for (int i = 0; i < cs.length; i++) {
if(cs[i] instanceof Owned) {
if(cs[i] instanceof BitRateControl) {
brc = (BitRateControl)cs;
if(brc.getBitRate()>0) {
brc.setBitRate(30000); done = true;
brc = null;
if(done) {
return ;
//then look for quality control
for (int i = 0; i < cs.length; i++) {
if(cs[i] instanceof Owned) {
if(cs[i] instanceof QualityControl) {
qc = (QualityControl)cs[i];
if(qc.getQuality()>0.0f) {
qc.setQuality(0.5f);
done = true;
qc = null;
if(done) {
return ;
//if that did not work, try setting frame rate
for (int i = 0; i < cs.length; i++) {
if(cs[i] instanceof Owned) {
if(cs[i] instanceof FrameRateControl) {
frc = (FrameRateControl)cs[i];
frc.setFrameRate(6.0f);
frc = null;
This will reduce your H.263 codec's bit rate to 80kbps. You cannot set less than that. I tried with many webcams and that's the least I could go.
Good luck. -
Httpurlconnection chunked output stream?
Hi,
I'm developing a client that interacts with a comet server (comet allows http connections to be used for multiple inputs and outputs on same connection -- not single request, single response). I've found that I can't use HttpURLConnection because it doesn't allow writing to its output stream after any input has been read from its input stream. It seems that httpURLConn.getInputStream() basically closes the output stream. Is there any way around this? Any way to write to an httpurlconnection's output stream after a read on its input has occurred?
For now I have to resort to using raw sockets and dealing with headers and chunked encoding manually. I'd sure love an easier way...
Thanks for any help,
PeterGet a new HTTPURLConnection. Java will cache it behind the scenes to reuse the same TCP connection.
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