Question

I have a function for sending data over Socket class in Java. When I send data I need to receive some data. The problem is how to set a timeout for waiting data on 2sec (if I don’t receive data in 2sec I need to understand that happened a communication error and show a message).
This is my code, any help?

    public boolean SendMonitorMessage(
            final MonitorRequestRepeatMessageTCP message) {
        boolean result = true;
        System.out
                .println("****************** SEND MONITOR REQUEST REPEAT MESSAGE TCP **********************************");

        // new Thread() {
        // public void run() {
        int prevService=message.GetService();
        synchronized (socket) {
            try {
                System.out.println("IPADDRESS=" + ipAddress);
                System.out.println("PORT=" + port);
                System.out.println("Is reachable=" + Ping());
                message.PrintMessage(message.toBytes());

                OutputStream socketOutputStream = (OutputStream) socket
                        .getOutputStream();
                socketOutputStream.write(message.toBytes());

                InputStream socketInputStream = (InputStream) socket
                        .getInputStream();
                
                byte[] buffer = new byte[256];
                List<byte[]> received = new LinkedList<byte[]>();
                int numberReceived;
                byte[] tempBuffer;

                while ((numberReceived = socketInputStream.read(buffer)) != -1) {
                    tempBuffer = new byte[numberReceived];
                    ByteBuffer baferce = ByteBuffer.wrap(tempBuffer);
                    baferce.put(buffer, 0, numberReceived);
                    received.add(tempBuffer);
                }
                
                if (received.size()>0){
                    new MonitorResponseMessageTCP(received, message.GetMonitorVariablesArrayList(), prevService);
                }
            } catch (UnknownHostException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return true;
    }

Answer 1

See Socket and ServerSocket. Both classes have a setSoTimeout method to specify the maximum time to wait when waiting for connections or waiting to receive data. When that time has elapsed, the socket throws a SocketTimeoutException that you can handle with your error message or however you want.

You have to call setSoTimeout before performing the actions you want to have a timeout.

Prior to

while ((numberReceived = socketInputStream.read(buffer)) != -1) {

You’ll need to call

socket.setSoTimeout(2000);

And then add a catch(SocketTimeoutException) section to the try/catch block you already have.