grazie, mi mancavano InputStream e OutpuStream.
codice:
public class Client {

    private final String HOST = "host";
    private final int PORT = port;

    public static void main(String[] args) {
        Client c = new Client();
        c.sendFile();
    }

    private void sendFile() {
        try {
            Socket socket = new Socket(HOST, PORT);
            FileInputStream fis = new FileInputStream(System.getProperty("user.home") + "/booklog.log");
            OutputStream out = socket.getOutputStream();
            byte[] buf = new byte[1024];
            int read;
            while ((read = fis.read(buf)) != -1) {
                out.write(buf, 0, read);
            }
            fis.close();
            out.close();
        } catch (UnknownHostException ex) {
            System.out.println(ex.getMessage());
        } catch (IOException ex) {
            System.out.println(ex.getMessage());
        }
    }
}
codice:
public class MTManager implements Runnable {

    private final String DIR_SAVE = "/media/hd/ftp";
    private Socket socket;

    public MTManager(Socket socket) {
        this.socket = socket;
    }

    public void run() {
        try {
            InputStream is = socket.getInputStream();
            FileOutputStream fos = new FileOutputStream(new File(DIR_SAVE + "/booklog.log"), true);
            byte[] buf = new byte[1024];
            int read;
            while ((read = is.read(buf)) != -1) {
                fos.write(buf, 0, read);
            }
            fos.close();
            is.close();
        } catch (Exception e) {
            System.out.println(e.getMessage());
        } finally {
            try {
                socket.close();
            } catch (IOException e) {
                System.out.println(e.getMessage());
            }
        }
    }
}