AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Sockets problem          AppletTalk.com Forum Index -> Java Help View previous topic :: View next topic   Author Message Matt Guest Posted: Sat Feb 25, 2006 4:12 pm    Post subject: Sockets problem Hi all, I'm developing a server using ServerSocket. For each connection established with a client, a new thread is created for attending it. The thread task consists on basically writing data through the socket continuously. There is no socket reading work in my server. The point is that I'm not able to detect if the connection with the client is broken, in order to stop the corresponding thread. If, for example, the client application is halted suddenly, my server keeps on writing on the socket although there is nobody listening on the other side... I would like to detect the connection failure if the client "dissapears" for some reason, so that I can stop my thread and act in consecuence. I've tried with Socket.isConnected, Socket.isClosed and so on... unsuccessfully. Here is the code of my server thread: ******************************************** public void run() { PrintWriter writer = new PrintWriter( new OutputStreamWriter ( m_socket.getOutputStream())); m_socket.setKeepAlive(false); while(m_repeat) { writer.println(data); writer.flush(); Thread.sleep(500); if (!m_socket.isConnected()) m_repeat = false; } writer.close(); m_socket.close(); } ********************************************** Previously I have created a ServerSocket and called accept(), pasing the new socket to the thread (it is stored in m_socket). The line using m_socket.isConnected does not work, as I said. *** Another problem I have is that when I close the connection from the client by calling Socket.close(), the server keeps on working too! (But this point is less important for me in this case...) In summary: 1) How can I detect a connection failure or a client sudden disconnection from the server? 2) How can I close the connection correctly in the client, so that the server is notified? Could anybody help me? Am I doing something wrong? Thanks in advance, Matt Back to top Knute Johnson Guest Posted: Sat Feb 25, 2006 6:12 pm    Post subject: Re: Sockets problem Matt wrote: Quote: Hi all, I'm developing a server using ServerSocket. For each connection established with a client, a new thread is created for attending it. The thread task consists on basically writing data through the socket continuously. There is no socket reading work in my server. The point is that I'm not able to detect if the connection with the client is broken, in order to stop the corresponding thread. If, for example, the client application is halted suddenly, my server keeps on writing on the socket although there is nobody listening on the other side... I would like to detect the connection failure if the client "dissapears" for some reason, so that I can stop my thread and act in consecuence. I've tried with Socket.isConnected, Socket.isClosed and so on... unsuccessfully. Here is the code of my server thread: ******************************************** public void run() { PrintWriter writer = new PrintWriter( new OutputStreamWriter ( m_socket.getOutputStream())); m_socket.setKeepAlive(false); while(m_repeat) { writer.println(data); writer.flush(); Thread.sleep(500); if (!m_socket.isConnected()) m_repeat = false; } writer.close(); m_socket.close(); } ********************************************** Previously I have created a ServerSocket and called accept(), pasing the new socket to the thread (it is stored in m_socket). The line using m_socket.isConnected does not work, as I said. *** Another problem I have is that when I close the connection from the client by calling Socket.close(), the server keeps on working too! (But this point is less important for me in this case...) In summary: 1) How can I detect a connection failure or a client sudden disconnection from the server? 2) How can I close the connection correctly in the client, so that the server is notified? Could anybody help me? Am I doing something wrong? Thanks in advance, Matt Matt: I think that sooner but probably later your outbound write will fail because there is no aknowledgement from the client socket. I had a similar problem in a server/client program I just wrote. The only way I could think of to get a quicker notification was to create another thread that tries to read from the socket. When the client end is closed the read throws an immediate IOException. No data is ever read because the client doesn't do any writing and the read just blocks until the socket is closed. When the IOException is thrown I close the outbound socket and clean up. -- Knute Johnson email s/nospam/knute/ Back to top Matt Guest Posted: Sat Feb 25, 2006 7:12 pm    Post subject: Re: Sockets problem Knute Johnson wrote: Quote: Matt wrote: Hi all, I'm developing a server using ServerSocket. For each connection established with a client, a new thread is created for attending it. The thread task consists on basically writing data through the socket continuously. There is no socket reading work in my server. The point is that I'm not able to detect if the connection with the client is broken, in order to stop the corresponding thread. If, for example, the client application is halted suddenly, my server keeps on writing on the socket although there is nobody listening on the other side... I would like to detect the connection failure if the client "dissapears" for some reason, so that I can stop my thread and act in consecuence. I've tried with Socket.isConnected, Socket.isClosed and so on... unsuccessfully. Here is the code of my server thread: ******************************************** public void run() { PrintWriter writer = new PrintWriter( new OutputStreamWriter ( m_socket.getOutputStream())); m_socket.setKeepAlive(false); while(m_repeat) { writer.println(data); writer.flush(); Thread.sleep(500); if (!m_socket.isConnected()) m_repeat = false; } writer.close(); m_socket.close(); } ********************************************** Previously I have created a ServerSocket and called accept(), pasing the new socket to the thread (it is stored in m_socket). The line using m_socket.isConnected does not work, as I said. *** Another problem I have is that when I close the connection from the client by calling Socket.close(), the server keeps on working too! (But this point is less important for me in this case...) In summary: 1) How can I detect a connection failure or a client sudden disconnection from the server? 2) How can I close the connection correctly in the client, so that the server is notified? Could anybody help me? Am I doing something wrong? Thanks in advance, Matt Matt: I think that sooner but probably later your outbound write will fail because there is no aknowledgement from the client socket. I had a similar problem in a server/client program I just wrote. The only way I could think of to get a quicker notification was to create another thread that tries to read from the socket. When the client end is closed the read throws an immediate IOException. No data is ever read because the client doesn't do any writing and the read just blocks until the socket is closed. When the IOException is thrown I close the outbound socket and clean up. Thank you very much Knute, It's surprising the fact that no support for connection monitoring is provided by Socket... but I've tried your solution and works fine :) I'd like to point out that, as far as i have seen, no IOException is thrown when the client closes the connection. The readLine method call which I use is blocking, and it just returns when the client is killed. Anyway, it works. Thank you very much for your help. Matt Back to top Steve Horsley Guest Posted: Mon Feb 27, 2006 11:12 pm    Post subject: Re: Sockets problem Knute Johnson wrote: Quote: Matt wrote: Hi all, I'm developing a server using ServerSocket. For each connection established with a client, a new thread is created for attending it. The thread task consists on basically writing data through the socket continuously. There is no socket reading work in my server. The point is that I'm not able to detect if the connection with the client is broken, in order to stop the corresponding thread. If, for example, the client application is halted suddenly, my server keeps on writing on the socket although there is nobody listening on the other side... I would like to detect the connection failure if the client "dissapears" for some reason, so that I can stop my thread and act in consecuence. I've tried with Socket.isConnected, Socket.isClosed and so on... unsuccessfully. Here is the code of my server thread: ******************************************** public void run() { PrintWriter writer = new PrintWriter( new OutputStreamWriter ( m_socket.getOutputStream())); m_socket.setKeepAlive(false); while(m_repeat) { writer.println(data); writer.flush(); Thread.sleep(500); if (!m_socket.isConnected()) m_repeat = false; } writer.close(); m_socket.close(); } ********************************************** Previously I have created a ServerSocket and called accept(), pasing the new socket to the thread (it is stored in m_socket). The line using m_socket.isConnected does not work, as I said. *** Another problem I have is that when I close the connection from the client by calling Socket.close(), the server keeps on working too! (But this point is less important for me in this case...) In summary: 1) How can I detect a connection failure or a client sudden disconnection from the server? 2) How can I close the connection correctly in the client, so that the server is notified? Could anybody help me? Am I doing something wrong? Thanks in advance, Matt Matt: I think that sooner but probably later your outbound write will fail because there is no aknowledgement from the client socket. I had a similar problem in a server/client program I just wrote. The only way I could think of to get a quicker notification was to create another thread that tries to read from the socket. When the client end is closed the read throws an immediate IOException. No data is ever read because the client doesn't do any writing and the read just blocks until the socket is closed. When the IOException is thrown I close the outbound socket and clean up. I don't think the reading is necessary. Once the TCP stack knows that the connection is broken, the next write call will fail with an exception anyway. The code above doesn't see it because PrintWriter swallows exceptions, IIRC. But an OutputStreamWriter should raise them. And you should be using an OutputStreamWriter anyway, so you can specify the character encoding, rather than just hoping that the platform default encoding will happen to suit the client. Steve 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.