webserv_linux.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUF_SIZE    1024
#define SMALL_BUF   100

void *request_handler(void *arg);
void send_data(FILE *fp, char *ct, char *file_name);
char *content_type(char *file);
void send_error(FILE *fp);

int main(int argc, char **argv) 
{
    int serv_sock, clnt_sock;
    struct sockaddr_in serv_addr, clnt_addr;
    socklen_t clnt_addr_size;
    char buf[BUF_SIZE];
    pthread_t t_id;

    if(argc != 2) {
        printf("Usage : %s <port>\n", argv[0]);
        return -1;
    }

    serv_sock = socket(AF_INET, SOCK_STREAM, 0);
    if(serv_sock < 0) {
        perror("socket");
        return -1;
    }
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(atoi(argv[1]));
    if(bind(serv_sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
        perror("bind");
        return -1;
    }
    
    if(listen(serv_sock, 5) < 0) {
        perror("listen");
        return -1;
    }

    while(1) {
        clnt_addr_size = sizeof(clnt_addr);
        clnt_sock = accept(serv_sock, (struct sockaddr *)&clnt_addr, &clnt_addr_size); 
        if(clnt_sock < 0) {
            perror("accept");
            return -1;
        }
        printf("Connection Request : %s:%d\n",
                inet_ntoa(clnt_addr.sin_addr), ntohs(clnt_addr.sin_port));
        pthread_create(&t_id, NULL, request_handler, (void *)&clnt_sock);
        pthread_detach(t_id);
    }
    
    close(serv_sock);
    return 0;
}

void *request_handler(void *arg)
{
    int clnt_sock = *((int *)arg);
    char req_line[SMALL_BUF];
    FILE *clnt_read;
    FILE *clnt_write;

    char method[10];
    char ct[15];
    char file_name[30];
  
    // 파일 포인터로 제어하기 위해 fd를 fp로 전환
    clnt_read = fdopen(clnt_sock, "r");
    clnt_write = fdopen(dup(clnt_sock), "w");
    fgets(req_line, SMALL_BUF, clnt_read);

    // 먼저 HTTP 프로토콜인지 확인하기 위해 strstr 함수로 substring을 찾음
    if(strstr(req_line, "HTTP/") == NULL) {
        send_error(clnt_write);
        fclose(clnt_read);
        fclose(clnt_write);
        return NULL;
    }
    
    /*
        요청 라인은 예를 들어
        GET /index.html HTTP/1.1로 구성되어 있다
    */

    // strtok에 ' ', '/'을 delimeter로 해서 추출한다
    strcpy(method, strtok(req_line, " /"));   // GET
    strcpy(file_name, strtok(NULL, " /"));    // index.html
    strcpy(ct, content_type(file_name));      // text.html

    if(strcmp(method, "GET") != 0) {
        send_error(clnt_write);
        fclose(clnt_read);
        fclose(clnt_write);
        return NULL;
    }
    if(strcmp(file_name, "index.html") != 0) {
        send_error(clnt_write);
        fclose(clnt_read);
        fclose(clnt_write);
        return NULL;
    }
     
    fclose(clnt_read);
    send_data(clnt_write, ct, file_name);
    return NULL;
}

void send_data(FILE *fp, char *ct, char *file_name)
{
    /* 
       응답 헤더
    */

    char protocol[] = "HTTP/1.0 200 OK\r\n";
    char server[] = "Server:Linux Web Server \r\n";
    char cnt_len[] = "Content-length:2048\r\n";
    char cnt_type[SMALL_BUF];
    char buf[BUF_SIZE];
    FILE *send_file;

    sprintf(cnt_type, "Content-type:%s\r\n\r\n", ct); // 마지막에 개행 2번을 해줘야 한다
    send_file = fopen(file_name, "r");
    if(send_file == NULL) {
        send_error(fp);
        return;
    }

    /* 헤더 정보 전송 */
    fputs(protocol, fp);
    fputs(server, fp);
    fputs(cnt_len, fp);
    fputs(cnt_type, fp);

    // html 정보 전달
    while(fgets(buf, BUF_SIZE, send_file) != NULL) {
        fputs(buf, fp);
        fflush(fp);
    }
    fflush(fp);
    fclose(fp);
    return;
}

char *content_type(char *file) 
{
    char extension[SMALL_BUF];
    char file_name[SMALL_BUF];
    strcpy(file_name, file);
    strtok(file_name, ".");
    strcpy(extension, strtok(NULL, "."));

    if(!strcmp(extension, "html") || !strcmp(extension, "htm"))
        return "text/html";
    else
        return "text/plain";
}

void send_error(FILE *fp)
{
    char protocol[] = "HTTP/1.0 400 Bad Request\r\n";
    char server[] = "Server:Linux Web Server \r\n";
    char cnt_len[] = "Content-length:2048\r\n";
    char cnt_type[] = "Content-type:text/html\r\n\r\n";
    char content[] = "<html><head><title>NETWORK</title></head>"
        "<body><font size=+5><br>Error"
        "</font></body></html>";

    fputs(protocol, fp);
    fputs(server, fp);
    fputs(cnt_len, fp);
    fputs(cnt_type, fp);
    fputs(content, fp);
    fflush(fp);
    return;
}