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Thread: Socket connection problem

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    Default Socket connection problem

    Hi,

    I have been working on an application which basically involves client to server socket communication. I was first testing the program from two terminal prompts (server and client) where they have been successfully connecting via locahost, which was OK.

    Now I started moving on from localhost by using a virtual machine using Virtualbox where the physical host being the server and the virtual machine being the client. The VM is bridged to the Local Network and has it's own IP address (they both can ping each other).

    When I try to create a socket connection from the client (virtual machine VM) to the server (physical host), I get a ' ConnectionException - Connection timed out: connect ' error.

    The snippets of code below show's their socket creation.

    //Create a socket to listen on port 3002
    ServerSocket ss = new ServerSocket(3002);
     
    //create input streams, read data etc...

    //Create a socket connection to the physical host 'doug-pc'
    Socket sClient = new Socket("doug-PC", 3002);
     
    //create output streams, write data etc...

    Can anyone identify the problem?

    Thanks, much appreciated


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    Default Re: Socket connection problem

    //open the connection
    InetAddress hostAddr = InetAddress.getByName(IPADDRESS);
    int hostPort = PORT;
    Socket soc = new Socket(hostAddr,hostPort);
    //Send value to server
    PrintWriter theWriter = new PrintWriter(soc.getOutputStream(),true);
    theWriter.println("Hi from client ");
    //receive the data from the server
    String input = "NoValue";
    BufferedReader theReader = new BufferedReader(new InputStreamReader(soc.getInputStream()));
    while((input = theReader.readLine()) != null)
    System.out.println("SERVER REPLIED : " + input + "\n");
    //close the socket ,I/O stream
    theReader.close();
    theWriter.close();
    soc.close();

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    Default Re: Socket connection problem

    If I'm not mistaken, the error is in
    Socket sClient = new Socket("doug-PC", 3002);
    If "doug-PC" is not mapped to an IP in your hosts file, than it may be treated as an IP itself. You should try to either map "doug-PC" to that host's real IP in your hosts file, or write a real IP itself instead of "doug-PC".

    I'm not sure about my answer, but I think it worth trying.

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    Default Re: Socket connection problem

    Thanks for the replies.

    I invoked the getByName() method using the host's IP address (192.168.1.12) on InetAddress as instructed. But again I still get the same error?

    Yes it does seem very much so that the client socket is causing the problem. There would be no point mapping "doug-PC" to "192.168.1.12" because I can ping the host by it's hostname, and it returns the correct IP address to the client's terminal?

    Could there be some other obvious problem here? Can Virtual Machines be troublesome when applying java networking?

    Thanks again

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    Super Moderator Norm's Avatar
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    Default Re: Socket connection problem

    Try another port.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Socket connection problem

    Yes I could try another port, but the two terminals on the host are connecting fine. So I wouldn't need to worry about the ports, I don't think.

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    Default Re: Socket connection problem

    Your choice.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Socket connection problem

    Firstly I know coordinates is probably the wrong terminology? I'd assume i'd simply be passing the x and y variables, but coordinates describe it better I feel.

    Now I need to have a Server which can be accessed by 2 clients, it is a racing game and it requires each client to be able to maneuver a racecar simultaniously, each using a different control scheme but that's neither here nor there.

    I was hoping someone would be able to assist me when it came to sending the x and y positions of a racecar to the server and having the server send them onto the next player and vice versa to allow both racecars to move at the same time on each clients window. So far i've only done the simple server stuff, such as the knock knock server on the sun website, and a simple echo server which repeats a string I send to the server.

    When I tried to use int instead of string I recieved an error that the int I wanted to pass was dynamic (obviously changes with each movement) and cannot be passed as static (using readInt and writeInt).

    So any help on how to create the wanted movement on both client windows through the server would be appreciated.

    Thanks

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