fork_server.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>
#include <netdb.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>

#define PORT    "80" /* Port to listen on */
#define BACKLOG     10  /* Passed to listen() */
#define BUFSIZE  8096

struct {
    char *ext;
    char *filetype;
} extensions [] = {
    {"gif", "image/gif" },
    {"jpg", "image/jpeg"},
    {"jpeg","image/jpeg"},
    {"png", "image/png" },
    {"zip", "image/zip" },
    {"gz",  "image/gz"  },
    {"tar", "image/tar" },
    {"htm", "text/html" },
    {"html","text/html" },
    {"exe","text/plain" },
    {0,0} 
};

/* Signal handler to reap zombie processes */
static void wait_for_child(int sig)
{
    while (waitpid(-1, NULL, WNOHANG) > 0);
}

void handle(int newsock)
{
	int j, file_fd, buflen, len;
    	long i, ret;
    	char * fstr;
    	static char buffer[BUFSIZE+1];
	ret = read(newsock,buffer,BUFSIZE);   /* 讀取瀏覽器要求 */
    if (ret==0||ret==-1) {
     /* 網路連線有問題，所以結束行程 */
        exit(3);
    }

    /* 程式技巧：在讀取到的字串結尾補空字元，方便後續程式判斷結尾 */
    if (ret>0&&ret<BUFSIZE)
        buffer[ret] = 0;
    else
        buffer[0] = 0;

    /* 移除換行字元 */
    for (i=0;i<ret;i++) 
        if (buffer[i]=='\r'||buffer[i]=='\n')
            buffer[i] = 0;
    
    /* 只接受 GET 命令要求 */
    if (strncmp(buffer,"GET ",4)&&strncmp(buffer,"get ",4))
        exit(3);
    /* 我們要把 GET /index.html HTTP/1.0 後面的 HTTP/1.0 用空字元隔開 */
    for(i=4;i<BUFSIZE;i++) {
        if(buffer[i] == ' ') {
            buffer[i] = 0;
            break;
        }
    }
    /* 檔掉回上層目錄的路徑『..』 */
    for (j=0;j<i-1;j++)
        if (buffer[j]=='.'&&buffer[j+1]=='.')
            exit(3);

    /* 當客戶端要求根目錄時讀取 index.html */
    if (!strncmp(&buffer[0],"GET /\0",6)||!strncmp(&buffer[0],"get /\0",6) )
        strcpy(buffer,"GET /index.html\0");

    /* 檢查客戶端所要求的檔案格式 */
    buflen = strlen(buffer);
    fstr = (char *)0;

    for(i=0;extensions[i].ext!=0;i++) {
        len = strlen(extensions[i].ext);
        if(!strncmp(&buffer[buflen-len], extensions[i].ext, len)) {
            fstr = extensions[i].filetype;
            break;
        }
    }

    /* 檔案格式不支援 */
    if(fstr == 0) {
        fstr = extensions[i-1].filetype;
    }

    /* 開啟檔案 */
    if((file_fd=open(&buffer[5],O_RDONLY))==-1)
  write(newsock, "Failed to open file", 19);

    /* 傳回瀏覽器成功碼 200 和內容的格式 */
    sprintf(buffer,"HTTP/1.0 200 OK\r\nContent-Type: %s\r\n\r\n", fstr);
    write(newsock,buffer,strlen(buffer));


    /* 讀取檔案內容輸出到客戶端瀏覽器 */
    while ((ret=read(file_fd, buffer, BUFSIZE))>0) {
        write(newsock,buffer,ret);
    }

    exit(1);	
}

int main(void)
{
    int sock;
    struct sigaction sa;
    struct addrinfo hints, *res;
    int reuseaddr = 1; /* True */

    /* Get the address info */
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    if (getaddrinfo(NULL, PORT, &hints, &res) != 0) {
        perror("getaddrinfo");
        return 1;
    }

    /* Create the socket */
    sock = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
    if (sock == -1) {
        perror("socket");
        return 1;
    }

    /* Enable the socket to reuse the address */
    if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &reuseaddr, sizeof(int)) == -1) {
        perror("setsockopt");
        return 1;
    }

    /* Bind to the address */
    if (bind(sock, res->ai_addr, res->ai_addrlen) == -1) {
        perror("bind");
        return 1;
    }

    /* Listen */
    if (listen(sock, BACKLOG) == -1) {
        perror("listen");
        return 1;
    }

    freeaddrinfo(res);

    /* Set up the signal handler */
    sa.sa_handler = wait_for_child;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_RESTART;
    if (sigaction(SIGCHLD, &sa, NULL) == -1) {
        perror("sigaction");
        return 1;
    }

    /* Main loop */
    while (1) {
        struct sockaddr_in their_addr;
        socklen_t size = sizeof(struct sockaddr_in);
        int newsock = accept(sock, (struct sockaddr*)&their_addr, &size);
        int pid;

        if (newsock == -1) {
            perror("accept");
            return 0;
        }

        printf("Got a connection from %s on port %d\n", inet_ntoa(their_addr.sin_addr),
                        htons(their_addr.sin_port));

        pid = fork();
        if (pid == 0) {
            /* In child process */
            close(sock);
            handle(newsock);
            return 0;
        }
        else {
            /* Parent process */
            if (pid == -1) {
                perror("fork");
                return 1;
            }
            else {
                close(newsock);
            }
        }
    }

    close(sock);

    return 0;
}