HTTP server in C

main.c

#include "server.c"

char *body = "<a>href='#'>Test</a>";
char *res = strcat(strcat("HTTP/1.1 200 OK\nDate: Mon, 27 Jul 2019 12:28:53 GMT\nServer: Apache/2.2.14 (Win32)\nLast-Modified: Wed, 22 Jul 2009 19:15:56 GMT\nContent-Length: ", str(strlen(body))), "\nContent-Type: text/html\nConnection: Closed\nContent-Type: text/html; charset=utf-8\n\n");


int handle_conn(int sock)
{
    write(sock, res, strlen(res));    
}

int main()
{
    HTTPServer serv;
    
    HTTPServerHost(&serv, 8050);

    HTTPServerOnConnect(&serv, &handle_conn);
}

server.c

#pragma once

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

#define HTTP_ERR_SOCKINIT 1
#define HTTP_ERR_SOCKBIND 2
#define HTTP_ERR_SOCKLSTN 3
typedef struct {
    unsigned int port;
    int sockId;
} HTTPServer;

void HTTPServerHost(HTTPServer *server, unsigned int port)
{
    server->port = port;
    server->sockId = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (server->sockId == -1)
    {
        return HTTP_ERR_SOCKINIT;
    }

    // Initializing socket address
    struct sockaddr_in addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = htonl(INADDR_ANY);


    if (bind(server->sockId, (struct sockaddr*) &addr, sizeof addr) == -1)
    {
        return HTTP_ERR_SOCKBIND;
    }

    if (listen(server->sockId, 10) == -1)
    {
        return HTTP_ERR_SOCKLSTN;
    }
}

void HTTPServerOnConnect(HTTPServer *server, int (*handler)(int))
{
    for (;;) {
        int ConnectFD = accept(server->sockId, NULL, NULL);

        if (0 > ConnectFD) {
            perror("accept failed");
            close(server->sockId);
            exit(EXIT_FAILURE);
        }
        
        handler(ConnectFD);
        
        if (shutdown(ConnectFD, SHUT_RDWR) == -1) {
            perror("shutdown failed");
            close(ConnectFD);
            close(server->sockId);
            exit(EXIT_FAILURE);
        }
        close(ConnectFD);
    }

    close(server->sockId);
}