Try this (top of this forum) thread: Networking Resources
>Bottom up learning is inefficient.
Some devs look at the docs as something they're not - they approach them as **tutorials**, when in fact they are **reference** material.
Remember - you have the docs, guides and sample apps.
Study sample code for implementation examples of whichever OS features. Each sample code project is a build-able and executable source example of how to accomplish a task for a specific technology. They show the correct sequence of calls and parameter data types to provide a generalized method for API use that developers can modify for their specific needs. Sample code is typically intended to show programming techniques and illustrate use of technology rather than suggest user interface designs (that's what the HIGs are for). Scan the readme with each sample and don't forget to check the comments in each file.
If there are samples you would like to see to illustrate particular technologies or techniques that are not covered by existing samples, feel free to file a bug report/enhancement...link is below right, every page here.
If you want an understanding of how everything fits together, as noted, you should read one of the associated Guides.