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Thread: Java - Socket Programming

  1. #1
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    Exclamation Java - Socket Programming

    I am new to Socket Programming. I know this is simple question but I want to learn this.

    I am trying with simple example sending a message between client and server. But I am getting error and I couldn't figure what is the problem. Can Some one please help.

    How can I get the output (if I run the app.java alone) as

    From Process 6
    Message sent to client is 12

    From Server 12

    App.java---------------------->


    import java.io.IOException;


    public class App {

    public static void main(String args[]) throws IOException{

    try {


    Master master_objec = new Master();
    master_objec.start();

    Process process_object = new Process();
    process_object.start();

    }
    catch (Exception e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
    }

    }
    }


    Master.java-------------------->
    public class Master {


    ServerSocket master_socket = null;
    private static Socket master_listen = null;
    final int PORT_NUMBER = 10004;
    PrintWriter printWriter = null;
    BufferedReader bufferedReader = null;


    public void start() throws IOException
    {
    try
    {

    master_socket = new ServerSocket(PORT_NUMBER);
    System.out.println("Server started. Awaiting connection requests...");

    while(true){
    //Input Stream
    master_listen = master_socket.accept();
    InputStream is = master_listen.getInputStream();
    InputStreamReader isr = new InputStreamReader(is);
    BufferedReader br = new BufferedReader(isr);
    int process_time = br.read();
    System.out.println("From Process "+ process_time);



    //Out put stream
    OutputStream os = master_listen.getOutputStream();
    OutputStreamWriter osw = new OutputStreamWriter(os);
    BufferedWriter bw = new BufferedWriter(osw);
    int new_process_time = process_time*2;
    bw.write(new_process_time);
    System.out.println("Message sent to the client is "+new_process_time);
    bw.flush();
    }
    }catch(IOException ioexception)
    {
    System.out.println("Error");

    }

    finally
    {
    try
    {
    master_listen.close();
    }
    catch(Exception e){}
    }
    }

    }


    Process.java------------------------------------>


    public class Process {


    private static Socket connects = null;
    int process_time =6;

    public void start() throws IOException{
    int port = 10004;
    connects = new Socket("localhost", port);

    OutputStream os = connects.getOutputStream();
    OutputStreamWriter osw = new OutputStreamWriter(os);
    BufferedWriter bw = new BufferedWriter(osw);
    bw.write(process_time);
    System.out.println("Message sent to the Server is "+process_time);
    bw.flush();


    InputStream is = connects.getInputStream();
    InputStreamReader isr = new InputStreamReader(is);
    BufferedReader br = new BufferedReader(isr);
    int process_time_new = br.read();
    System.out.println("From Master "+ process_time_new);


    }
    }

    This is the output I am getiing:

    java.net.BindException: Address already in use: JVM_Bind
    at java.net.DualStackPlainSocketImpl.bind0(Native Method)
    at java.net.DualStackPlainSocketImpl.socketBind(Unkno wn Source)
    at java.net.AbstractPlainSocketImpl.bind(Unknown Source)
    at java.net.PlainSocketImpl.bind(Unknown Source)
    at java.net.ServerSocket.bind(Unknown Source)
    at java.net.ServerSocket.<init>(Unknown Source)
    at java.net.ServerSocket.<init>(Unknown Source)
    at Master.start(Master.java:28)
    at App.main(App.java:12)
    Message sent to the Server is 6
    From Master 6
    Last edited by smylalwys; October 10th, 2014 at 07:49 AM.


  2. #2
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    Default Re: Java - Socket Programming

    The message says it all. The address you are trying to use is already being used by an other Socket. Each address can only be used once at a time.
    Perhaps you didnt kill your JVM properly when testing before or maybe another program is using this same address.

  3. #3
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    Default Re: Java - Socket Programming

    Hi Cornix,

    I even tried changing the port number but then when I run App.java, It just keep waiting for connection... saying
    Server started. Awaiting connection requests...

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    Default Re: Java - Socket Programming

    This thread has been cross posted here:

    http://www.java-forums.org/networking/93187-java-socket-programming.html

    Although cross posting is allowed, for everyone's benefit, please read:

    Java Programming Forums Cross Posting Rules

    The Problems With Cross Posting


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    Default Re: Java - Socket Programming

    Welcome to the forum! Please read this topic to learn how to post code in code or highlight tags and other useful info for new members.

    Please post your code correctly using code or highlight tags per the above link.

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