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  • Waiting for ServerSocket accept() to put socket into "listen" mode

    - by inazaruk
    I need a simple client-server communication in order to implement unit-test. My steps: Create server thread Wait for server thread to put server socket into listen mode ( serverSocket.accept() ) Create client Make some request, verify responses Basically, I have a problem with step #2. I can't find a way to signal me when server socket is put to "listen" state. An asynchronous call to "accept" will do in this case, but java doesn't support this (it seems to support only asynchronous channels and those are incompatible with "accept()" method according to documentation). Of cause I can put a simple "sleep", but that is not really a solution for production code. So, to summarize, I need to detect when ServerSocket has been put into listen mode without using sleeps and/or polling.

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  • Reading POST data from html form sent to serversocket.

    - by user32167
    i try to write simplest possible server app in Java, displaying html form with textarea input, which after submitting gives me possibility to parse xml typed in that textarea. For now i build simple serversocket based server like that: import java.io.BufferedReader; import java.io.InputStreamReader; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; public class WebServer { protected void start() { ServerSocket s; String gets = ""; System.out.println("Start on port 80"); try { // create the main server socket s = new ServerSocket(80); } catch (Exception e) { System.out.println("Error: " + e); return; } System.out.println("Waiting for connection"); for (;;) { try { // wait for a connection Socket remote = s.accept(); // remote is now the connected socket System.out.println("Connection, sending data."); BufferedReader in = new BufferedReader(new InputStreamReader( remote.getInputStream())); PrintWriter out = new PrintWriter(remote.getOutputStream()); String str = "."; while (!str.equals("")) { str = in.readLine(); if (str.contains("GET")){ gets = str; break; } } out.println("HTTP/1.0 200 OK"); out.println("Content-Type: text/html"); out.println(""); // Send the HTML page String method = "get"; out.print("<html><form method="+method+">"); out.print("<textarea name=we></textarea></br>"); out.print("<input type=text name=a><input type=submit></form></html>"); out.println(gets); out.flush(); remote.close(); } catch (Exception e) { System.out.println("Error: " + e); } } } public static void main(String args[]) { WebServer ws = new WebServer(); ws.start(); } } After form (textarea with xml and one additional text input) is submitted in 'gets' String-type variable I have Urlencoded values of my variables (also displayed on the screen, it looks like that: gets = GET /?we=%3Cnetwork+ip_addr%3D%2210.0.0.0%2F8%22+save_ip%3D%22true%22%3E%0D%0A%3Csubnet+interf_used%3D%22200%22+name%3D%22lan1%22+%2F%3E%0D%0A%3Csubnet+interf_used%3D%22254%22+name%3D%22lan2%22+%2F%3E%0D%0A%3C%2Fnetwork%3E&a=fooBar HTTP/1.1 What can i do to change GET to POST method (if i simply change it in form and than put " if (str.contains("POST")){" it gives me string like gets = POST / HTTP/1.1 with no variables. And after that, how i can use xml from my textarea field (called 'we')?

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  • [java] reading POST data from html form sent to serversocket.

    - by user32167
    i try to write simplest possible server app in Java, displaying html form with textarea input, which after submitting gives me possibility to parse xml typed in thet textarea. For now i build simple serversocket based server like that: import java.io.BufferedReader; import java.io.InputStreamReader; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; public class WebServer { protected void start() { ServerSocket s; String gets = ""; System.out.println("Start on port 80"); try { // create the main server socket s = new ServerSocket(80); } catch (Exception e) { System.out.println("Error: " + e); return; } System.out.println("Waiting for connection"); for (;;) { try { // wait for a connection Socket remote = s.accept(); // remote is now the connected socket System.out.println("Connection, sending data."); BufferedReader in = new BufferedReader(new InputStreamReader( remote.getInputStream())); PrintWriter out = new PrintWriter(remote.getOutputStream()); String str = "."; while (!str.equals("")) { str = in.readLine(); if (str.contains("GET")){ gets = str; break; } } out.println("HTTP/1.0 200 OK"); out.println("Content-Type: text/html"); out.println(""); // Send the HTML page String method = "get"; out.print("<html><form method="+method+">"); out.print("<textarea name=we></textarea></br>"); out.print("<input type=text name=a><input type=submit></form></html>"); out.println(gets); out.flush(); remote.close(); } catch (Exception e) { System.out.println("Error: " + e); } } } public static void main(String args[]) { WebServer ws = new WebServer(); ws.start(); } } After form (textarea with xml and one additional text input) is submitted in 'gets' String-type variable I have Urlencoded values of my variables (also displayed on the screen, it looks like that: gets = GET /?we=%3Cnetwork+ip_addr%3D%2210.0.0.0%2F8%22+save_ip%3D%22true%22%3E%0D%0A%3Csubnet+interf_used%3D%22200%22+name%3D%22lan1%22+%2F%3E%0D%0A%3Csubnet+interf_used%3D%22254%22+name%3D%22lan2%22+%2F%3E%0D%0A%3C%2Fnetwork%3E&a=fooBar HTTP/1.1 What can i do to change GET to POST method (if i simply change it in form and than put " if (str.contains("GET")){" it gives me string like gets = POST / HTTP/1.1 with no variables. And after that, how i can use xml from my textarea field (called 'we')?

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  • What to do when ServerSocket throws IOException and keeping server running

    - by s5804
    Basically I want to create a rock solid server. while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... } catch (IOException e) { e.printStackTrace(); // NOW WHAT? } } In the IOException block, what to do? Is the Server socket at fault so it need to be recreated? For example wait a few seconds and then serverSocket = ServerSocketFactory.getDefault().createServerSocket(MY_PORT); However if the server socket is still OK, then it is a pity to close it and kill all previously accepted connections that are still communicating. EDIT: After some answers, here my attempt to deal with the IOException. Would the implementation be guaranteeing keeping the server up and only re-create server socket when only necessary? while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... bindExceptionCounter = 0; } catch (IOException e) { e.printStackTrace(); recreateServerSocket(); } } private void recreateServerSocket() { while (keepRunning) { try { logger.info("Try to re-create Server Socket"); ServerSocket socket = ServerSocketFactory.getDefault().createServerSocket(RateTableServer.RATE_EVENT_SERVER_PORT); // No exception thrown, then use the new socket. serverSocket = socket; break; } catch (BindException e) { logger.info("BindException indicates that the server socket is still good.", e); bindExceptionCounter++; if (bindExceptionCounter < 5) { break; } } catch (IOException e) { logger.warn("Problem to re-create Server Socket", e); e.printStackTrace(); try { Thread.sleep(30000); } catch (InterruptedException ie) { logger.warn(ie); } } } }

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  • Java ServerSocket Multiple Listen Instances

    - by ikurtz
    i have a java game app that uses sockets to communicate with each other. the issue is when i do a socket listen (server), i can run another instance of the game on the same machine using the same port as before to listen, and it results in listening again. now i have two instances of the application both listening on the same port. you can imagine only one connects when a connection comes through. the question is: how do i prevent the app from listening on the same port as another instance is already listening to? thanks in advance. EDIT: serverSocket = new ServerSocket(serverPort, backlog); im using this. should i try to use: ServerSocket(int port, int backlog, InetAddress bindAddr) instead? EDIT: SOLVED! i did not handle the exception only trapped it. now it is working well. thanks for your inputs.

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  • [java] Efficiency of while(true) ServerSocket Listen

    - by Submerged
    I am wondering if a typical while(true) ServerSocket listen loop takes an entire core to wait and accept a client connection (Even when implementing runnable and using Thread .start()) I am implementing a type of distributed computing cluster and each computer needs every core it has for computation. A Master node needs to communicate with these computers (invoking static methods that modify the algorithm's functioning). The reason I need to use sockets is due to the cross platform / cross language capabilities. In some cases, PHP will be invoking these java static methods. I used a java profiler (YourKit) and I can see my running ServerSocket listen thread and it never sleeps and it's always running. Is there a better approach to do what I want? Or, will the performance hit be negligible? Please, feel free to offer any suggestion if you can think of a better way (I've tried RMI, but it isn't supported cross-language. Thanks everyone

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  • Efficiency of while(true) ServerSocket Listen

    - by Submerged
    I am wondering if a typical while(true) ServerSocket listen loop takes an entire core to wait and accept a client connection (Even when implementing runnable and using Thread .start()) I am implementing a type of distributed computing cluster and each computer needs every core it has for computation. A Master node needs to communicate with these computers (invoking static methods that modify the algorithm's functioning). The reason I need to use sockets is due to the cross platform / cross language capabilities. In some cases, PHP will be invoking these java static methods. I used a java profiler (YourKit) and I can see my running ServerSocket listen thread and it never sleeps and it's always running. Is there a better approach to do what I want? Or, will the performance hit be negligible? Please, feel free to offer any suggestion if you can think of a better way (I've tried RMI, but it isn't supported cross-language. Thanks everyone

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  • What to do when ServerSocket throws IOException

    - by s5804
    Basically I want to create a rock solid server. while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... } catch (IOException e) { e.printStackTrace(); // NOW WHAT? } } In the IOException block, what to do? Is the Server socket at fault so it need to be recreated? For example wait a few seconds and then serverSocket = ServerSocketFactory.getDefault().createServerSocket(MY_PORT); However if the server socket is still OK, then it is a pity to close it and kill all previously accepted connections that are still communicating.

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  • Socksifying a Java ServerSocket - how to approach

    - by Thorbjørn Ravn Andersen
    I would like to have a Java program running on network A have a ServerSocket living on another network B through a proxy. I have played with a SOCKS5 proxy (which works) but it appears that all the proxy facilities in Java only work with client connections, not with ServerSockets (no constructor taking a Proxy argument). Asking Google gives much hay and few needles. What is the approach I should take to get this running? If a specific client is better than a generic SOCKS or web proxy then fine, but it needs to be Java (that leaves sshd out). Target JVM is preferrably Java 5, and then Java 6.

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  • How can I interrupt a ServerSocket accept() method?

    - by lukeo05
    Hi, In my main thread I have a while(listening) loop which calls accept() on my ServerSocket object, then starts a new client thread and adds it to a Collection when a new client is accepted. I also have an Admin thread which I want to use to issue commands, like 'exit', which will cause all the client threads to be shut down, shut itself down, and shut down the main thread, by turning listening to false. However, the accept() call in the while(listening) loop blocks, and there doesn't seem to be any way to interrupt it, so the while condition cannot be checked again and the program cannot exit! Is there a better way to do this? Or some way to interrupt the blocking method? Thanks!

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  • Android app unexpectedly quitted when I closed the bluetooth serversocket or bluetooth socket

    - by Lewisou
    The android app quitted without any warning and error when bluetoothServersocket.close() called in the main thread while bluetoothServersocket.accept(); was blocked for incoming connections in another thread. Here is pieces of my code. public void run() { try { bluetoothServerSocket = BluetoothAdapter. getDefaultAdapter().listenUsingRfcommWithServiceRecord(LISTEN_NAME, LISTEN_UUID); /* the thread blocked here for incoming connections */ bluetoothSocket = bluetoothServerSocket.accept(); ... } catch(Exception e) {} finally { try {bluetoothServerSocket.close();} catch(Exception ex) {} try {bluetoothSocket.close();} catch(Exception ex) {} } } And in the activity. public void onStop () { try{thread.bluetoothSocket.close();} catch(Exception ex) {} try{thread.bluetoothServerSocket.close();} catch(Exception ex) {} super.onStop(); } When I clicked the back button. The activity closed but after about one second the app quitted without any warning. My android os version is 2.2. a HTC Desire device.

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  • Connect two client sockets

    - by Hernán Eche
    Good morning, let's say Java has two kind of sockets... server sockets "ServerSocket" client sockets or just "Socket" ////so Simple ! Imagine the situation of two processes: X Client <-- Y Server The server process Y : has a "ServerSocket", that is listening to a TCP port The client process X : send a connection request through a -client type- "Socket" X ////so Simple ! then the accept() method (in server Y) returns a new client type "Socket", when it occurs, great the two Sockets get "interconected", so the -client socket- in client process, is connected with the -client socket- in the server process then (reading/writing in socket X is like reading/writing in socket Y, and viceversa. ) TWO CLIENT SOCKETS GET INTERCONECTED!! ////so Simple ! BUT... (there is always a But..) What if I create the two CLIENT sockets in same process, and I want to get them "interconected" ? ////mmm Complex =(... even posible? Let's say how to have TWO CLIENT SOCKETS GET INTERCONECTED WITHOUT using an intermediate ServerSocket ? I 've solved it.. by creating two threads for continuously reading A and writing B, and other for reading B and writng A... but I think could be a better way..(or should!) (Those world-energy-consuming threads are not necessary with the client-server aproach) Any help or advice would be appreciated!! Thanks

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  • tried to update hudson via dashboard and now it doesn;t work (windows)

    - by Tim
    I get the following now in the output log. I really wish I hadn't attempted to update teh version. What a hassle. Can anyone diagnose the issue here? Running from: C:\hudson\hudson.war [Winstone 2010/06/14 23:33:54] - Beginning extraction from war file hudson home directory: C:\hudson [Winstone 2010/06/14 23:33:56] - Error during HTTP listener init or shutdown java.net.SocketException: Unrecognized Windows Sockets error: 0: JVM_Bind at java.net.PlainSocketImpl.socketBind(Native Method) at java.net.PlainSocketImpl.bind(Unknown Source) at java.net.ServerSocket.bind(Unknown Source) at java.net.ServerSocket.(Unknown Source) at java.net.ServerSocket.(Unknown Source) at winstone.HttpListener.getServerSocket(HttpListener.java:102) at winstone.HttpListener.run(HttpListener.java:116) at java.lang.Thread.run(Unknown Source) [Winstone 2010/06/14 23:33:56] - HTTP Listener shutdown successfully [Winstone 2010/06/14 23:33:56] - Winstone Servlet Engine v0.9.10 running: controlPort=disabled [Winstone 2010/06/14 23:33:56] - Error during AJP13 listener init or shutdown java.net.SocketException: Unrecognized Windows Sockets error: 0: JVM_Bind at java.net.PlainSocketImpl.socketBind(Native Method) at java.net.PlainSocketImpl.bind(Unknown Source) at java.net.ServerSocket.bind(Unknown Source) at java.net.ServerSocket.(Unknown Source) at java.net.ServerSocket.(Unknown Source) at winstone.ajp13.Ajp13Listener.run(Ajp13Listener.java:99) at java.lang.Thread.run(Unknown Source) [Winstone 2010/06/14 23:33:56] - AJP13 Listener shutdown successfully Running from: C:\hudson\hudson.war [Winstone 2010/06/14 23:38:49] - Beginning extraction from war file hudson home directory: C:\hudson [Winstone 2010/06/14 23:38:51] - Winstone Servlet Engine v0.9.10 running: controlPort=disabled [Winstone 2010/06/14 23:38:51] - Error during AJP13 listener init or shutdown java.net.SocketException: Unrecognized Windows Sockets error: 0: JVM_Bind at java.net.PlainSocketImpl.socketBind(Native Method) at java.net.PlainSocketImpl.bind(Unknown Source) at java.net.ServerSocket.bind(Unknown Source) at java.net.ServerSocket.(Unknown Source) at java.net.ServerSocket.(Unknown Source) at winstone.ajp13.Ajp13Listener.run(Ajp13Listener.java:99) at java.lang.Thread.run(Unknown Source) [Winstone 2010/06/14 23:38:51] - AJP13 Listener shutdown successfully [Winstone 2010/06/14 23:38:51] - Error during HTTP listener init or shutdown java.net.SocketException: Unrecognized Windows Sockets error: 0: JVM_Bind at java.net.PlainSocketImpl.socketBind(Native Method) at java.net.PlainSocketImpl.bind(Unknown Source) at java.net.ServerSocket.bind(Unknown Source) at java.net.ServerSocket.(Unknown Source) at java.net.ServerSocket.(Unknown Source) at winstone.HttpListener.getServerSocket(HttpListener.java:102) at winstone.HttpListener.run(HttpListener.java:116) at java.lang.Thread.run(Unknown Source) [Winstone 2010/06/14 23:38:51] - HTTP Listener shutdown successfully

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  • Java multithreaded server - each connection returns data. Processing on main thread?

    - by oliwr
    I am writing a client with an integrated server that should wait indefinitely for new connections - and handle each on a Thread. I want to process the received byte array in a system wide available message handler on the main thread. However, currently the processing is obviously done on the client thread. I've looked at Futures, submit() of ExecutorService, but as I create my Client-Connections within the Server, the data would be returned to the Server thread. How can I return it from there onto the main thread (in a synchronized packet store maybe?) to process it without blocking the server? My current implementation looks like this: public class Server extends Thread { private int port; private ExecutorService threadPool; public Server(int port) { this.port = port; // 50 simultaneous connections threadPool = Executors.newFixedThreadPool(50); } public void run() { try{ ServerSocket listener = new ServerSocket(this.port); System.out.println("Listening on Port " + this.port); Socket connection; while(true){ try { connection = listener.accept(); System.out.println("Accepted client " + connection.getInetAddress()); connection.setSoTimeout(4000); ClientHandler conn_c= new ClientHandler(connection); threadPool.execute(conn_c); } catch (IOException e) { System.out.println("IOException on connection: " + e); } } } catch (IOException e) { System.out.println("IOException on socket listen: " + e); e.printStackTrace(); threadPool.shutdown(); } } } class ClientHandler implements Runnable { private Socket connection; ClientHandler(Socket connection) { this.connection=connection; } @Override public void run() { try { // Read data from the InputStream, buffered int count; byte[] buffer = new byte[8192]; InputStream is = connection.getInputStream(); ByteArrayOutputStream out = new ByteArrayOutputStream(); // While there is data in the stream, read it while ((count = is.read(buffer)) > 0) { out.write(buffer, 0, count); } is.close(); out.close(); System.out.println("Disconnect client " + connection.getInetAddress()); connection.close(); // handle the received data MessageHandler.handle(out.toByteArray()); } catch (IOException e) { System.out.println("IOException on socket read: " + e); e.printStackTrace(); } return; } }

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  • What happens to an instance of ServerSocket blocked inside accept(), when I drop all references to i

    - by Hanno Fietz
    In a multithreaded Java application, I just tracked down a strange-looking bug, realizing that what seemed to be happening was this: one of my objects was storing a reference to an instance of ServerSocket on startup, one thread would, in its main loop in run(), call accept() on the socket while the socket was still waiting for a connection, another thread would try to restart the component under some conditions, the restart process missed the cleanup sequence before it reached the initialization sequence as a result, the reference to the socket was overwritten with a new instance, which then wasn't able to bind() anymore the socket which was blocking inside the accept() wasn't accessible anymore, leaving a complete shutdown and restart of the application as the only way to get rid of it. Which leaves me wondering: with no references left to the ServerSocket instance, what would free the socket for a new connection? At what point would the ServerSocket become garbage collected? In general, what are good practices I can follow to avoid this type of bug?

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  • Question regarding TCP Connection Forcefully shut down.

    - by Tara Singh
    Hi All, I am designing a Client Server Chat application in Java which uses TCP connection between them. I am not able to figure out how to detect at server side when a client forcefully closes down. I need this as i am maintaining a list of online clients and i need to remove user from the list when he forcefully closes the connection. Any help will be highly appreciated. Thanks Tara Singh

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  • How to recive more than 65000 bytes in C++ socket using recv()

    - by Mr.Cool
    I am developing a client server application (TCP) in Linux using C++. I want to send more than 65,000 bytes at the same time. In TCP, the maximum packet size is 65,635 bytes only. How can I send the entire bytes without loss? Following is my code at server side. //Receive the message from client socket if((iByteCount = recv(GetSocketId(), buffer, MAXRECV, MSG_WAITALL)) > 0) { printf("\n Received bytes %d\n", iByteCount); SetReceivedMessage(buffer); return LS_RESULT_OK; } If I use MSG_WAITALL it takes a long time to receive the bytes so how can I set the flag to receive more than 10 lakhs bytes at time.

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  • Close resources before exiting JFrame and TCP communication in Java

    - by Oz Molaim
    1. I'm writing a chat based application on TCP communication. I'm using NetBeans and I want to add functionality to the default EXIT_ON_CLOSE when exiting JFrame. The reason of course is because I want to clean resources and end threads safely. How can I call a method that clear resources and only then close the JFrame safely and end the process. 2. I need to implement the server side. The server has List/HashMap/Queue of 'Socket' with their chat nick-names. Is there any simple design pattern to do it correctly because I don't want to re-invent the wheel. thanks.

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  • How to find out on which internet addresses a java program can listen.

    - by tzador
    My program needs to listen incoming socket connections (lets agree on port 8765), but it doesn't know which addresses it can bind on a particular machine. Of, course, it could simply to listen to all of them, but it need to send to the client program over a different(slower) channel the addresses which it should try in order to rich me on port 8765. So the flow is like this: My program lisens on all available interfaces on port 8765 Finds out a list of inet4 adresses by which it can be possibly reached (this step is the actual question) Posts that address on a whiteboard (blogpost or something) Interested clients try out all of them, to see using which one they can reach my program. This is all is to be done in java ofcourse :)

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  • Examples of bad variable names and reasons [on hold]

    - by user470184
    I'll start with a class in the jdk package : public final class Sdp { should be : public final class SocketsDirectProtocol { Sdp is class name, this is ambigious, should be : Class<?> cl = Class.forName("java.net.SdpSocketImpl", true, null); should be : Class<?> clazz = Class.forName("java.net.SdpSocketImpl", true, null); cl is ambiguous private static void setAccessible(final AccessibleObject o) { should be : private static void setAccessible(final AccessibleObject accessibleObject) { There are various other examples in this class, do you have similar and/or differing examples of variables that were named badly ? package com.oracle.net; public final class Sdp { private Sdp() { } /** * The package-privage ServerSocket(SocketImpl) constructor */ private static final Constructor<ServerSocket> serverSocketCtor; static { try { serverSocketCtor = (Constructor<ServerSocket>) ServerSocket.class.getDeclaredConstructor(SocketImpl.class); setAccessible(serverSocketCtor); } catch (NoSuchMethodException e) { throw new AssertionError(e); } } /** * The package-private SdpSocketImpl() constructor */ private static final Constructor<SocketImpl> socketImplCtor; static { try { Class<?> cl = Class.forName("java.net.SdpSocketImpl", true, null); socketImplCtor = (Constructor<SocketImpl>)cl.getDeclaredConstructor(); setAccessible(socketImplCtor); } catch (ClassNotFoundException e) { throw new AssertionError(e); } catch (NoSuchMethodException e) { throw new AssertionError(e); } } private static void setAccessible(final AccessibleObject o) { AccessController.doPrivileged(new PrivilegedAction<Void>() { public Void run() { o.setAccessible(true); return null; } }); } /** * SDP enabled Socket. */ private static class SdpSocket extends Socket { SdpSocket(SocketImpl impl) throws SocketException { super(impl); } } /** * Creates a SDP enabled SocketImpl */ private static SocketImpl createSocketImpl() { try { return socketImplCtor.newInstance(); } catch (InstantiationException x) { throw new AssertionError(x); } catch (IllegalAccessException x) { throw new AssertionError(x); } catch (InvocationTargetException x) { throw new AssertionError(x); } } /** * Creates an unconnected and unbound SDP socket. The {@code Socket} is * associated with a {@link java.net.SocketImpl} of the system-default type. * * @return a new Socket * * @throws UnsupportedOperationException * If SDP is not supported * @throws IOException * If an I/O error occurs */ public static Socket openSocket() throws IOException { SocketImpl impl = createSocketImpl(); return new SdpSocket(impl); } /** * Creates an unbound SDP server socket. The {@code ServerSocket} is * associated with a {@link java.net.SocketImpl} of the system-default type. * * @return a new ServerSocket * * @throws UnsupportedOperationException * If SDP is not supported * @throws IOException * If an I/O error occurs */ public static ServerSocket openServerSocket() throws IOException { // create ServerSocket via package-private constructor SocketImpl impl = createSocketImpl(); try { return serverSocketCtor.newInstance(impl); } catch (IllegalAccessException x) { throw new AssertionError(x); } catch (InstantiationException x) { throw new AssertionError(x); } catch (InvocationTargetException x) { Throwable cause = x.getCause(); if (cause instanceof IOException) throw (IOException)cause; if (cause instanceof RuntimeException) throw (RuntimeException)cause; throw new RuntimeException(x); } } /** * Opens a socket channel to a SDP socket. * * <p> The channel will be associated with the system-wide default * {@link java.nio.channels.spi.SelectorProvider SelectorProvider}. * * @return a new SocketChannel * * @throws UnsupportedOperationException * If SDP is not supported or not supported by the default selector * provider * @throws IOException * If an I/O error occurs. */ public static SocketChannel openSocketChannel() throws IOException { FileDescriptor fd = SdpSupport.createSocket(); return sun.nio.ch.Secrets.newSocketChannel(fd); } /** * Opens a socket channel to a SDP socket. * * <p> The channel will be associated with the system-wide default * {@link java.nio.channels.spi.SelectorProvider SelectorProvider}. * * @return a new ServerSocketChannel * * @throws UnsupportedOperationException * If SDP is not supported or not supported by the default selector * provider * @throws IOException * If an I/O error occurs */ public static ServerSocketChannel openServerSocketChannel() throws IOException { FileDescriptor fd = SdpSupport.createSocket(); return sun.nio.ch.Secrets.newServerSocketChannel(fd); } }

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  • Limit Connections with semaphores

    - by Robert
    I'm trying to limit the number of connections my server will accept using semaphores, but when running, my code doesn't seem to make this restriction - am I using the semaphore correctly? eg. I have hardcoded the number of permit as 2, but I can connect an unlimited number of clients... public class EServer implements Runnable { private ServerSocket serverSocket; private int numberofConnections = 0; private Semaphore sem = new Semaphore(2); private volatile boolean keepProcessing = true; public EServer(int port) throws IOException { serverSocket = new ServerSocket(port); } @Override public void run() { while (keepProcessing) { try { sem.acquire(); Socket socket = serverSocket.accept(); process(socket, getNextConnectionNumber()); } catch (Exception e) { } finally { sem.release(); } } closeIgnoringException(serverSocket); } private synchronized int getNextConnectionNumber() { return ++numberofConnections; } // processing related methods }

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  • Can Java ServerSocket and Sockets using ObjectIOStreams lose packets?

    - by Joel Garboden
    I'm using a ServerSocket on my server and Sockets that use ObjectIOStreams to send serializable objects over the network connection. I'm developing an essentially more financial version of monopoly and thus packets being sent and confirmed as sent/received is required. Do I need to implement my own packet loss watcher or is that already taken care of with (Server)Sockets? I'm primarily asking about losing packets during network blips or whatnot, not full connection error. E.g. siblings move a lead plate between my router and computer's wi-fi adapter. http://code.google.com/p/inequity/source/browse/#svn/trunk/src/network Code can be found under network-ClientController and network-Server

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  • Java Stop Server Thread

    - by ikurtz
    the following code is server code in my app: private int serverPort; private Thread serverThread = null; public void networkListen(int port){ serverPort = port; if (serverThread == null){ Runnable serverRunnable = new ServerRunnable(); serverThread = new Thread(serverRunnable); serverThread.start(); } else { } } public class ServerRunnable implements Runnable { public void run(){ try { //networkConnected = false; //netMessage = "Listening for Connection"; //networkMessage = new NetworkMessage(networkConnected, netMessage); //setChanged(); //notifyObservers(networkMessage); ServerSocket serverSocket = new ServerSocket(serverPort, backlog); commSocket = serverSocket.accept(); serverSocket.close(); serverSocket = null; //networkConnected = true; //netMessage = "Connected: " + commSocket.getInetAddress().getHostAddress() + ":" + //commSocket.getPort(); //networkMessage = new NetworkMessage(networkConnected, netMessage); //setChanged(); //notifyObservers(networkMessage); } catch (IOException e){ //networkConnected = false; //netMessage = "ServerRunnable Network Unavailable"; //System.out.println(e.getMessage()); //networkMessage = new NetworkMessage(networkConnected, netMessage); //setChanged(); //notifyObservers(networkMessage); } } } The code sort of works i.e. if im attempting a straight connection both ends communicate and update. The issue is while im listening for a connection if i want to quit listening then the server thread continues running and causes problems. i know i should not use .stop() on a thread so i was wondering what the solution would look like with this in mind? EDIT: commented out unneeded code.

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  • How do I abort a socket.recv() from another thread in python?

    - by Samuel Skånberg
    I have a main thread that waits for connection. It spawns client threads that will echo the response from the client (telnet in this case). But say that I want to close down all sockets and all threads after some time, like after 1 connection. How would I do? If I do clientSocket.close() from the main thread, it won't stop doing the recv. It will only stop if I first send something through telnet, then it will fail doing further sends and recvs. My code look like this: # Echo server program import socket from threading import Thread import time class ClientThread(Thread): def __init__(self, clientSocket): Thread.__init__(self) self.clientSocket = clientSocket def run(self): while 1: try: # It will hang here, even if I do close on the socket data = self.clientSocket.recv(1024) print "Got data: ", data self.clientSocket.send(data) except: break self.clientSocket.close() HOST = '' PORT = 6000 serverSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) serverSocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) serverSocket.bind((HOST, PORT)) serverSocket.listen(1) clientSocket, addr = serverSocket.accept() print 'Got a new connection from: ', addr clientThread = ClientThread(clientSocket) clientThread.start() time.sleep(1) # This won't make the recv in the clientThread to stop immediately, # nor will it generate an exception clientSocket.close()

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  • How can i get a file from remote machine?

    - by programmerist
    How can i get a file from remote computer? i know remote computer ip and 51124 port is open. i need this algorith: 1) Connect 192.xxx.x.xxx ip via 51124 port 2) filename:123456 (i want to search it on remote machine) 3) Get File 4) Save C:\ 51124 port is open. can i access and can i search any file according to filename? My code is below: IPEndPoint ipEnd = new IPEndPoint(IPAddress.Any, 51124); Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP); sock.Bind(ipEnd); sock.Listen(maxConnections); Socket serverSocket = sock.Accept(); byte[] data = new byte[bufferSize]; int received = serverSocket.Receive(data); int filenameLength = BitConverter.ToInt32(data, 0); string filename = Encoding.ASCII.GetString(data, 4, filenameLength); BinaryWriter bWrite = new BinaryWriter(File.Open(outPath + filename, FileMode.Create)); bWrite.Write(data, filenameLength + 4, received - filenameLength - 4); int received2 = serverSocket.Receive(data); while (received2 0) { bWrite.Write(data, 0, received2); received2 = serverSocket.Receive(data); } bWrite.Close(); serverSocket.Close(); sock.Close();

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