OPC connection establishment

I am a newbie. I have searched various forums for opc application. It seem they are using US SDKs to create opc client and server application. I have gone through Unified automation SDK and i am sucessful to connect, read and write. But i need to create my own opc application. I wanted to know how to connect opc server and client without using any external SDKs or application. In my first step i want to know the communication packet required to establish the connection in between server and client. I have tried wireshark to see the communication packet but i couldnot figure them out.

I want to make a simple program in c++ to establish connection in between opc client and server and preferrably a opc UA.

I also think that i am doing it wrong way to make opc application. What can be the right step to start working to develop opc client and opc server.

Could you please help me. I have been stuck in this problem for a long time.

Regards, Sika