Chapter 2: So what are we building?
The actual final end goal is going to remain a mystery for the time being, but what I can tell you is that we are going to be building a server!
What is a server? It's a program that accepts incoming connections, reads and writes to that connection and closing it eventually.
You will hear the term socket used a lot in this project. Sockets are a way of connecting two devices on a network together. One socket listens, the other socket connects.
The main design of sockets in the unix world is Berkeley Sockets and on windows it's Winsock.
This project will mostly be using berkeley sockets but if you want to use windows APIs feel free.
In general there is a flow for sockets. On the client you follow a flow like this;
+---------+
| Connect |
+---+-----+
|
+---v--+
+---> Send |
| +---+--+
| |
| +---v--+
+---+ Recv |
+---+--+
|
+---v---+
| Close |
+-------+
First the client connects. Then the client can send and receive (recv) data until the connection is finally closed.
On the server the flow is slightly more involved.
+------+ +--------+ +--------+ +------+ +------+ +-------+
| Bind +---> Listen +---> Accept +---> Recv +---> Send +---> Close |
+------+ +---^----+ +---+----+ +--^---+ +--+---+ +-------+
| | | |
+------------+ +----------+
When a server starts up and creates a socket, it binds that socket to an interface and a port. The server will then set the socket to listening for connections, when a connection comes in it needs to accept that connection. Once a connection has been accepted it can receive and send to the socket the same as the client and eventually close it.
This overview is brushing over a few details and you are encouraged to do your own research
Goals
- Read up on sockets.
- Find the documentation on your languages bindings for sockets.