network protocol

[passer-by]

I am trying to write a server program that collects data from devices. This program is supposed to replace
the old one (we buy it abroad). But I don't have any documentation the way server program communicates with devices
In order to understand the exchange protocol I use Wireshark sniffer.

A Proper protocol from wireshark

Client -> Syn
Server -> Ack Syn
Client -> Ack syn
Client -> <INI> string
Server -> ACK string
Client -> <RDY>
Server -> 0B0B11040101000101050000 string
Client -> <ACK>01
Client -> Data
...

But in my way after recieving <RDY> string server and client exchenges by the ack messages. And client sends <RDY> once again. Is it possible to avoid this exchanging?

This is a cutting of my code:

try{
            String inputLine;                                              //Here strings from client will be stored
            String ack = "ACK" + "\r";                                     //answer from server to <INI> line from wcl
            String ackAdd = "\r\n";
            String hex = "0B0B11040101000101050000";                       //read index from client

            /*Get the input and output I/O steams from socket
            * */

            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            OutputStream out = socket.getOutputStream();
            DataOutputStream dos = new DataOutputStream(out);
while ((inputLine = in.readLine()) != null){
                if((inputLine.toUpperCase()).contains("<INI>")){
                    jta.append("Wavecell with IP" + socket.toString() + " tries to connect to server" + inputLine + "\n");

                    dos.writeBytes(ack);                             //send ack to <INI> command from wcl
                    dos.flush();
                    dos.writeBytes(ackAdd);
                    dos.flush();

                }else if((inputLine.toUpperCase()).contains("<RDY>")){
                    dos.writeBytes(hex);                             //now we can request the data index
                    dos.flush();
                    dos.write(ackAdd);
                    dos.flush();
                }else if ((inputLine.toUpperCase()).contains("<ANS>")){
                    dos.writeBytes("0404010000");
                    dos.flush();
                    dos.writeBytes();
                    dos.flush();
                }
            } 
            
            out.close();
            dos.close();
            socket.close();

        }catch (IOException ex){
            logger.log(Level.SEVERE, "Problems with getting I/O streams ");
            System.exit(-1);
        }
}