Random SocketException: Connection reset

As I mentioned in this question, I was getting a SocketException: Connection reset.
After implemented Aaron's answer it seems to be working as intended. But today that I run the code again, I got once again the connection reset error.
The problem is that if I run my code like 5 times, it seems to work 2/5 times and the rest gives me the error...

Server:

import java.io.*;
import java.net.*;

public class Server {

    public static void main(String[] args) throws IOException, ClassNotFoundException {       
            ServerSocket server = new ServerSocket(444);
            while (true) {
                Socket socket = server.accept();
                ObjectInputStream objIn = new ObjectInputStream(socket.getInputStream());
                Object objRead = objIn.readObject();
                if (objRead != null) {
                    System.out.println(objRead);
                }
            }       
    }
}

Client:

import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
import java.util.HashMap;

public class Client {

    public static void main(String[] args) throws IOException {
        Socket sock;
        int port = 444;
        HashMap<Integer, String>  mapSend= new HashMap<>();
        mapSend.put(1,"row1");
        mapSend.put(2,"row2");

        sock = new Socket(InetAddress.getLocalHost(), port);
        ObjectOutputStream objOut = new ObjectOutputStream(sock.getOutputStream());
        
        objOut.writeObject(mapSend);
        objOut.flush();
    }
}

This is the error: (it appears on the output of the server, after I run the client):

java.net.SocketException: Connection reset
    at java.net.SocketInputStream.read(SocketInputStream.java:189)
    at java.net.SocketInputStream.read(SocketInputStream.java:121)
    at java.io.ObjectInputStream$PeekInputStream.read(ObjectInputStream.java:2308)
    at java.io.ObjectInputStream$BlockDataInputStream.read(ObjectInputStream.java:2716)
    at java.io.ObjectInputStream$BlockDataInputStream.readFully(ObjectInputStream.java:2740)
    at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1978)
    at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1913)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1796)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1348)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:370)
    at java.util.HashMap.readObject(HashMap.java:1154)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:1017)
    at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1891)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1796)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1348)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:370)
    at iotest.Server.main(Server.java:16)

On the client side I get no errors.

EDIT
Any way I can debug the client-server? That might help out to give you guys more info on this.