java code explanation

public String getUserID(String usernmae, String password) {
        String flag = "";
        try {
            if (true) {
                socket = new Socket("localhost", 8080);
                dos = new DataOutputStream(socket.getOutputStream());
                dos.writeUTF("SignIn");
                dos.writeUTF(username);
                dos.writeUTF(password);
                dis = new DataInputStream(socket.getInputStream());
                response = dis.readUTF();
                String[] res_arr = response.split("#");
                if (res_arr[0].equalsIgnoreCase("record")) {
                    flag = "success";
                    userid = Integer.parseInt(res_arr[1]);
                    port = Integer.parseInt(res_arr[2]);
                    secretkey = res_arr[3];
                } else {
                    flag = "failure";
                    // System.out.println("Login Failed...");
                }
 
            }

Can anyone please explain this code. This is just a part of the program.
After entering the user name and password it is going to "response = getUserID(username, password);"

I am not able to understand at the line String[] res_arr=response.split("#");