Route Handling

We successfully ran our server in the previous chapter. Now we can start to receive requests and send responses.

Handlers

Let’s begin with classics; writing a hello world handler. First, create a handlers.c and handlers.h files in the src/ directory:

src/handlers.c

#include "router.h"

void hello_world(Req *req, Res *res)
{
    reply(res, "200 OK", "text/plain", "hello world!");
}

We include "router.h" header, which is the main module of our project. It provides various HTTP tools — such as Req, Res and reply() — used for writing handlers and routers.

We get the request via Req *req that we’ll see more detailed in the next chapter. Res *res is our response header, we send it in every response. And reply() is using for sending a response to the client.

When we are done with the handler, we should send a response to the client via reply() function. Basically, it takes 4 parameters:

• The res parameter,
• Status code,
• Content-Type,
• Response body

Now we must declare this handler function in a .h file — just like we always do when writing in C. We already created a handlers.h along with handlers.c file.

src/handlers.h

#ifndef HANDLERS_H
#define HANDLERS_H

#include "router.h"

void hello_world(Req *req, Res *res);

#endif

We declared our handler function but we are not done yet. We need to add handlers.c file to our CMakeLists.txt to compile it.

src/CMakeLists.txt

cmake_minimum_required(VERSION 3.10)
project(your-project VERSION 0.1.0 LANGUAGES C)

set(APP_SRC
    ${CMAKE_CURRENT_SOURCE_DIR}/main.c
    ${CMAKE_CURRENT_SOURCE_DIR}/handlers.c # WE ADDED OUR HANDLERS
    PARENT_SCOPE
)

Now we can write the router, which will run our hello_world handler when a request is received.

Declaring Routes

We can create our routers with get(), post(), put() and del() methods. Let’s update our main.c file like this:

src/main.c

#include "ecewo.h"     // This is for starting server
#include "router.h"      // This is for routing
#include "handlers.h"   // This is our handlers

int main()
{
    get("/", hello_world); // "GET" router for hello_world handler

    ecewo(4000);    // Start server
    return 0;   // Exit main function
}

get(), post(), put() and del() takes two parameters. First one is the path and second one is the handler.

Now we can recompile our program and go to http://localhost:4000/ again. We’ll receive this:

hello world!

So simple.

Notes

<--- NOTE 1 --->

We have to define our routes in the entry point, which is main.c. For modularity, we can define them outside and call in the int main() function.

<--- NOTE 2 --->

We have to use double quots "" to define the route path every time. If we accidentally write single quots '', we’ll get an error.

get("/", hello_world); // CORRECT
get('/', hello_world); // INCORRECT