Question

My JAVA application sends a command to server (command=filename.ini). When the server receives this command it sends filename.ini contents through Socket.
The first problem I had was receiving only partial contents of the file. That happened when in the code I used while(in.available()!=0){//write bytes} because in.available() does not know how big/long the content of the file is. If I use while((numBytesRead = dis.read(buffer)) != -1){//write bytes} the loop will never terminate since the Socket connection remains always open. My question is how else can I terminate the loop once every byte has been received? Please help me I have tried everything. I understand where the mistake is but I don’t know how to fix it.

The following is the part of the code I have at the moment:

public class TCPClient {

    protected Socket s = null;
    public DataInputStream in = null;

    public TCPClient(InetAddress ipa, int port) {

        Socket s1 = null;

        try { //Open the socket.
            s1 = new Socket(ipa.getHostAddress(), port);
        } catch (IOException ex) {
            System.out.println("Error opening socket!");
            return;
        }

        s = s1;

        try { //Create an input stream.
            in = new DataInputStream(new BufferedInputStream(s.getInputStream()));
        } catch (Exception ex) {
            System.out.println("Error creating input stream!");
        }
    }

    public synchronized byte[] receive() {

        byte[] buffer = new byte[0];

        ByteArrayOutputStream getBytes = new ByteArrayOutputStream();

        try {
            while (in.available() == 0) {
            }  //Wait for data.
        } catch (IOException ex) {
        }

        try {

            int numBytesRead;
            buffer = new byte[1024];

            while ((numBytesRead = dis.read(buffer, 0, 1024)) != -1) { //LOOP NEVER ENDS HERE BECAUSE CONNECTION IS ALWAYS OPEN
                getBytes.write(buffer, 0, numBytesRead);
            }


        } catch (IOException ex) {
        }

        return (getBytes.toByteArray());
    }
}

Answer 1

You need to define a micro protocol to say the receiver how long is the file, or just close the connection on the server after finishing sending the file. First method is preferred, since it is a little bit more robust. On the client you should have a timeout too in order to avoid to wait forever in case of network problems.

Clarification for micro protocol: before sending the file itself send a 32 (or 64 if needed) bit integer containing the file length. The client should read that integer and then start retrieving the file.