AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Sockets problem: getInputStream hanging          AppletTalk.com Forum Index -> Java Help View previous topic :: View next topic   Author Message Allan Bruce Guest Posted: Thu Jan 12, 2006 11:13 pm    Post subject: Sockets problem: getInputStream hanging I am starting Java network programming for the first time although I have experience in Java itself and socket programming in C++. I have an IM server already running which I use to communicate with C++ clients and that all runs fine. Now I want to develop a Java client but am having problems. When I connect the socket then try to get the input stream my program just hangs. The code is below, if anyone can tell me why this might happen, I would appreciate it. Another point is that, I want to send actual bytes on the line and receive actual bytes, what type of input/output stream should I be using? Thanks Allan private boolean connectToAServer() { System.out.println("Attempting to connect to a server..."); try { mSocket = new Socket(Globals.gPrefs.mainServer(), Globals.gPrefs.mainServerPort()); } catch (Exception e) { System.err.println("Could not connect to main server: " + e); } if (mSocket == null) { try { mSocket = new Socket(Globals.gPrefs.backupServer(), Globals.gPrefs.backupServerPort()); } catch (Exception e) { System.err.println("Could not connect to backup server: " + e); } } if (mSocket == null) return ERROR; System.out.println("Connection established on " + mSocket.getInetAddress()); try { mOutput = new ObjectOutputStream( mSocket.getOutputStream()); mOutput.flush(); mInput = new ObjectInputStream(mSocket.getInputStream()); // hangs here } catch (Exception e) { closeSocket(); return ERROR; } return OK; } Back to top Roedy Green Guest Posted: Thu Jan 12, 2006 11:21 pm    Post subject: Re: Sockets problem: getInputStream hanging On Thu, 12 Jan 2006 23:13:01 -0000, "Allan Bruce" <amb (AT) abc (DOT) net> wrote, quoted or indirectly quoted someone who said : Quote: mOutput = new ObjectOutputStream( mSocket.getOutputStream()); mOutput.flush(); mInput = new ObjectInputStream(mSocket.getInputStream()); // C/C++ won't have a clue how to create or read an ObjectStream. You want perhaps a DataOutputStream or a LEDataOutputStream. See http://mindprod.com/applets/fileio.html for sample code. -- Canadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. Back to top Allan Bruce Guest Posted: Fri Jan 13, 2006 1:11 am    Post subject: Re: Sockets problem: getInputStream hanging "Roedy Green" <my_email_is_posted_on_my_website (AT) munged (DOT) invalid> wrote in message news:72pds1ttfr6m5vrbjbcs3q38flkdquij3l (AT) 4ax (DOT) com... Quote: On Thu, 12 Jan 2006 23:13:01 -0000, "Allan Bruce" <amb (AT) abc (DOT) net> wrote, quoted or indirectly quoted someone who said : mOutput = new ObjectOutputStream( mSocket.getOutputStream()); mOutput.flush(); mInput = new ObjectInputStream(mSocket.getInputStream()); // C/C++ won't have a clue how to create or read an ObjectStream. You want perhaps a DataOutputStream or a LEDataOutputStream. See http://mindprod.com/applets/fileio.html for sample code. -- Canadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. Thanks, I have some successful comms now ) Can you help with the following: I have setup my socket as in my original post, and I can verify that it sends data fine to the server and I can read a packet. How can I setup this socket to listen for packets now? In C I would add them to a polling set and continually check this to see if any of my sockets had data on them. How would I implement this in Java? Thanks Allan Back to top Roedy Green Guest Posted: Fri Jan 13, 2006 2:08 am    Post subject: Re: Sockets problem: getInputStream hanging On Fri, 13 Jan 2006 01:11:59 -0000, "Allan Bruce" <amb (AT) abc (DOT) net> wrote, quoted or indirectly quoted someone who said : Quote: I have setup my socket as in my original post, and I can verify that it sends data fine to the server and I can read a packet. How can I setup this socket to listen for packets now? In C I would add them to a polling set and continually check this to see if any of my sockets had data on them. How would I implement this in Java? There are two sorts of thing you can do: 1. accept TCP/IP streaming socket connections from the outside world. Have a look at http://mindprod.com/products1.html#ECHOSERVER for the world's most mindless Java server. It shows you the essential trick. 2. accept UDP packets from the outside world. I don't have code for that handy. But you could get started by reading http://mindprod.com/jgloss/udp.html -- Canadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. Back to top Gordon Beaton Guest Posted: Fri Jan 13, 2006 7:38 am    Post subject: Re: Sockets problem: getInputStream hanging On Fri, 13 Jan 2006 01:11:59 -0000, Allan Bruce wrote: Quote: I have setup my socket as in my original post, and I can verify that it sends data fine to the server and I can read a packet. How can I setup this socket to listen for packets now? In C I would add them to a polling set and continually check this to see if any of my sockets had data on them. How would I implement this in Java? You have basically two choices: - create a thread to handle each connection, and use blocking read calls. - use a java.nio.channels.Selector, much the same way you would use select() in C to multiplex many connections on a single thread. /gordon -- [ do not email me copies of your followups ] g o r d o n + n e w s @ b a l d e r 1 3 . s e Back to top Allan Bruce Guest Posted: Fri Jan 13, 2006 3:30 pm    Post subject: Re: Sockets problem: getInputStream hanging "Gordon Beaton" <not (AT) for (DOT) email> wrote Quote: On Fri, 13 Jan 2006 01:11:59 -0000, Allan Bruce wrote: I have setup my socket as in my original post, and I can verify that it sends data fine to the server and I can read a packet. How can I setup this socket to listen for packets now? In C I would add them to a polling set and continually check this to see if any of my sockets had data on them. How would I implement this in Java? You have basically two choices: - create a thread to handle each connection, and use blocking read calls. - use a java.nio.channels.Selector, much the same way you would use select() in C to multiplex many connections on a single thread. /gordon Thanks Gordon, I have opted for the first option since I willonly ever have at most 5 sockets at the same time - but mainly i will only be using 1. Unless you can convince me otherwise? Thanks Allan Back to top Gordon Beaton Guest Posted: Fri Jan 13, 2006 3:46 pm    Post subject: Re: Sockets problem: getInputStream hanging On Fri, 13 Jan 2006 15:30:51 -0000, Allan Bruce wrote: Quote: I have opted for the first option since I willonly ever have at most 5 sockets at the same time - but mainly i will only be using 1. Unless you can convince me otherwise? That's the easier solution and sounds like it's ok for this project, but in time you'll find java.nio to be a useful skill. Your call. BTW since nobody's pointed it out yet, your original code was hanging in new ObjectInputStream(), not sock.getInputStream(). The ObjectInputStream constructor is stuck waiting for the peer to create a corresponding ObjectOutputStream and send a header. /gordon -- [ do not email me copies of your followups ] g o r d o n + n e w s @ b a l d e r 1 3 . s e Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         AppletTalk.com Forum Index -> Java Help All times are GMT Page 1 of 1   Jump to: Select a forum Java Newsgroups----------------Java DiscussionsWeb-based java games comp.lang.java 3D Graphics API's for Java Java: Support and criticism Java System Announcements comp.lang.java.api JavaBeans Java and CORBA Java and Databases comp.lang.java.developer Java GUI Toolkits Java Help comp.lang.java.javascript JVM, native methods and hardware comp.lang.java.misc Java Language Programming Security and Java comp.lang.java.setup Java Software Tools comp.lang.java.tech ibm.software.java.linux  Non-English Java Newsgroups----------------Java Language (German)Language Java (Français)Java (Italian)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.