cwebserver.c

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

//maximum application buffer
#define APP_MAX_BUFFER 1024
#define PORT 8080

int main (){
    //define the server and client file descriptors
    int server_fd, client_fd;

    //define the server's socket address
    struct sockaddr_in address;
    int address_len = sizeof(address);
 
    // Set up server socket address 
    address.sin_family = AF_INET; //ipv4
    address.sin_addr.s_addr = INADDR_ANY; //Binds to all network interfaces, for real production specify an explicit IP for security and control.
    address.sin_port = htons(PORT); 

    // Create socket
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        perror("Socket failed");
        exit(EXIT_FAILURE);
    }

    // Bind the socket to address
    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) {
        perror("Bind failed");
        exit(EXIT_FAILURE);
    }


    // Creates the queues 
    // Listen for clients, with 10 backlog (10 connections in accept queue)
    if (listen(server_fd, 10) < 0) {
        perror("Listen failed");
        exit(EXIT_FAILURE);
    }
    
    //define the server's application buffer where we receive the client requests
    char buffer[APP_MAX_BUFFER] = {0};

    //we loop forever
    while (1){
        printf("\nWaiting for a connection...\n");

        // Accept a client connection client_fd == connection
        // this blocks if there is no request

        // IMP - Creating a breakpoint here for example case of local host, load local host and then continue
        if ((client_fd = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&address_len)) < 0) {
            perror("Accept failed");
            exit(EXIT_FAILURE);
        }

        //reading client request
        //read data from the server's kernal receive buffer to the application (buffer)
        //this is essentially reading the HTTP request
        read(client_fd, buffer, APP_MAX_BUFFER);
        printf("%s\n", buffer);
 
        // We send the request by writing to the socket send buffer in the OS
        char *http_response = "HTTP/1.1 200 OK\n"
                      "Content-Type: text/plain\n"
                      "Content-Length: 13\n\n"
                      "Hello world!\n";

        //write to the socket
        //send queue os
        write(client_fd, http_response, strlen(http_response));
         

        //close the client socket (terminate the TCP connection)
        close(client_fd);
    }

    return 0;
}