Chapter 10: Methods and resources.
If you haven't guessed by now, we are writing a HTTP server. Not against the entire specification (though you can if you want) just against a limited subset that should work with a browser if you have done it correctly.
HTTP is a line delimited protocol. The idea being that a client will request content from a server and the server will
deliver it.
Each time one side delivers a line to the other it should be delimited by \r and \n which is carriage ret and line feed.
The start of a HTTP request is as follows.
[method] [resource] [http-version]\r\n
Methods
The methods are OPTIONS or GET or HEAD or POST or PUT or DELETE or TRACE or CONNECT
Some of these you might have experienced before, others are a bit more unusual.
GET is the simplest with "GET me this resource". Get is also considered idempotent which means the act of doing it again
should have identical results, cause no side effects, it can also be cached.
PUT is "PUT something at this resource". This method is also considered idempotent and is usually used to create or update a resource.
HEAD is identical to GET but doesn't return the resource, only the headers (more on headers and responses in the next chapter) and start of the request. It is also idempotent.
POST post is explicitly to create new entries at the located resource. It should not be cached and should not be considered idempotent.
DELETE deletes the resource given. It should be repeatable and is considered idempotent.
OPTIONS is kind of a query to see what is allowed on a given resource, it should reply with what methods are supported and any other information.
TRACE and CONNECT we are going to ignore these two as they are not commonly used anymore and wont be of much use to us.
Resource
A resource is just something identified by a URL. An example of a resource could be /index.html or /api/person
These are both resources, it's down to the server to decide what these resources mean. In a web application they might
correspond to a controller, or as a file on disk.
Version
The version tells the server what http version the client is using and can support, and the server replies with the same.
Goals
- Process an incoming request (you can use curl, wget, your browser to send requests)
- Read the first line and break it into a method, a resource and the version and then close the connection.
Bonus goals
- Log when a request is invalid (unknown method)