How to send a valid result of an arithmetic operation through DataOutputStream

I have a subprocess class that calculate the sum of two integers and then put it in a DataOutputStream:

public class SubProcess {
  public static void main(String[] args) throws IOException {
     DataInputStream in = new DataInputStream(System.in);
     DataOutputStream out = new DataOutputStream(System.out);
     int a = in.readInt();
     out.writeInt(a);
     int b = in.readInt();
     out.writeInt(b);
     int result = a+b;
     out.writeInt(result);
     out.flush();
     in.read();
     out.close();
     in.close();
    }
  } 

when writing the two values of a and b like 12 and 47 respectivley the result is "ei".

In another hand the mainprocess won't read that result like an DataInputStream through the ReadInt() line, and it throws an exception :

        Exception in thread "main" java.io.EOFException
            at java.io.DataInputStream.readInt(Unknown Source)
            at testthread.MainProcess.main(MainProcess.java:21)

It seems that the main process doesn't communicate really with the subprocess. deleting the package from the two classes and running the main process on cmd avoid the exception.