Because of the formulation of the question, I assume (please don't be irritated, if wrong) that you have very little knowledge of networking. In that case, it won't harm the Beej guide, but probably not the best point to start. The article discuses BGP protocol, which is totally absent in the linked guide. You may write literally millions of networking applications without need to know anything about BGP. Only if you are working in the backbone of the internet, you will encounter BGP, not even in big private networks. It will be a long way to really start from 0 up to BGP.