How to send a login POST/GET request and receive the response in c

Question

i'm learning about POSIX sockets in C language, and i'm curios on how to send a login request (for example Facebook) and actually verify that the login was succesfull. I know how i can retrieve the HTTP request, but i don't know how to past it in a c function, and how to send it with sockets.

I'm not asking for a full code implementation, i'm just asking what are the functions/libraries that could help me, how to use them and the steps i need to follow to accomplish the goal.

I really appreciate any help.

Answer 1

here is a snippet with comments to show you how to make a simple GET Request in C (Take note: I coded this with POSIX in mind)!:

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<netinet/in.h>

#define flags 0


int main() {

        int sock; // Sockets are int data type
        sock = socket(AF_INET, SOCK_STREAM, 0); //AF_INET = Internet Connection //SOCK_STREAM = TCP

        struct sockaddr_in server_host; //Struct type is a data type consisting of other data types inside. Similar to a 'class'

        struct timeval timeout;
        timeout.tv_sec = 1;  //Set Socket Timeout After 1 Second
        timeout.tv_usec = 0; //Therefore it will stop sending/receiving data
        setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout, sizeof(timeout));

        server_host.sin_family = AF_INET; //Family type of the connection
        server_host.sin_addr.s_addr = inet_addr("216.58.212.110"); //google.com's IP Address
        server_host.sin_port = htons(80); //HTTP Port = 80

        connect(sock, (struct sockaddr*)&server_host, sizeof(server_host));
        //This statement means:
        //Connect using the socket                                - connect(sock...
        //Convert 'server_host' to a 'sockaddr' type              - (struct sockaddr*)&server_host...
        //With a memory size of 'server_host' (however big it is) - sizeof(server_host)


        const char get_request[] = "GET / HTTP/1.0\r\n\r\n"; //This is a GET request. It asks for the site.

        send(sock, get_request, strlen(get_request), flags); //Send the get request
        //Send using socket 'sock' - send(sock...
        //Send data 'get_request'    - get_request, ...
        //How long 'get_request' is  - strlen(get_request), ...

        char * received_data = (char *)malloc(sizeof(char)*10000); //Gives 'received_data' 10000 From the RAM
        //recv(sock, received_data, 4096, flags);
        //Receive data using socket 'sock'     - recv(sock...
        //Put the data into 'received_data'      - received_data, ...
        //How much of 'received_data' to take up - 4096, ...

        do {
                char byte[1];
                recv(sock, byte, 1, flags);
                if(strcmp(byte, "") == 0) {
                        break;
                } else {
                        strcat(received_data, byte);
                        memset(byte,'\0',sizeof(byte));
                }
        } while(1==1);

        puts(received_data);

        close(sock);
        free(received_data); //REMEMBER TO DO THIS!!!!
        return 0;
}

I hope this helps!