Linux socket编程之web server

最新推荐文章于 2024-07-29 14:46:57 发布

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本文介绍了一个简易HTTP服务器的实现过程，包括源代码及其编译运行方法。该服务器通过监听特定端口接收请求，并能根据不同请求类型执行相应操作，如文件读取、目录列表展示等。

源码：

#include<stdio.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<string.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<netdb.h>
#define   BACKLOG  1
#define   HOSTLEN  256
main(int ac, char *av[])
{
    int     sock, fd;
    FILE    *fpin;
    char    request[BUFSIZ];

    if ( ac == 1 )
    {
        fprintf(stderr,"usage: ws portnum\n");
        exit(1);
    }
    sock = make_server_socket( atoi(av[1]) );
    if ( sock == -1 )
    {
        printf("cannot make server_socket!\n");
        exit(2);
    }
    /* main loop here */

    while(1)
    {
        /* take a call and buffer it */
        fd = accept( sock, NULL, NULL );
        fpin = fdopen(fd, "r" );

        /* read request */
        fgets(request,BUFSIZ,fpin);
        printf("got a call: request = %s", request);
        read_til_crnl(fpin);

        /* do what client asks */
        process_rq(request, fd);

        fclose(fpin);
    }
}

/* ------------------------------------------------------ *
 *    read_til_crnl(FILE *)
 *       skip over all request info until a CRNL is seen
 *          ------------------------------------------------------ */

read_til_crnl(FILE *fp)
{
    char    buf[BUFSIZ];
    while(fgets(buf,BUFSIZ,fp)!= NULL && strcmp(buf,"\r\n") != 0 );
}

/* ------------------------------------------------------ *
 *    process_rq( char *rq, int fd )
 *       do what the request asks for and write reply to fd
 *          handles request in a new process
 *             rq is HTTP command:  GET /foo/bar.html HTTP/1.0
 *                ------------------------------------------------------ */

process_rq( char *rq, int fd )
{
    char    cmd[BUFSIZ], arg[BUFSIZ];

    /* create a new process and return if not the child */
    if ( fork() != 0 )
        return;

    strcpy(arg, "./");      /* precede args with ./ */
    if ( sscanf(rq, "%s%s", cmd, arg+2) != 2 )
        return;

    if ( strcmp(cmd,"GET") != 0 )
        cannot_do(fd);
    else if ( not_exist( arg ) )
        do_404(arg, fd );
    else if ( isadir( arg ) )
        do_ls( arg, fd );
    else if ( ends_in_cgi( arg ) )
        do_exec( arg, fd );
    else
        do_cat( arg, fd );
}

/* ------------------------------------------------------ *
 *    the reply header thing: all functions need one
 *       if content_type is NULL then don't send content type
 *          ------------------------------------------------------ */

header( FILE *fp, char *content_type )
{
    fprintf(fp, "HTTP/1.0 200 OK\r\n");
    if ( content_type )
        fprintf(fp, "Content-type: %s\r\n", content_type );
}

/* ------------------------------------------------------ *
 *    simple functions first:
 *            cannot_do(fd)       unimplemented HTTP command
 *                and do_404(item,fd)     no such object
 *                   ------------------------------------------------------ */

cannot_do(int fd)
{
    FILE    *fp = fdopen(fd,"w");

    fprintf(fp, "HTTP/1.0 501 Not Implemented\r\n");
    fprintf(fp, "Content-type: text/plain\r\n");
    fprintf(fp, "\r\n");

    fprintf(fp, "That command is not yet implemented\r\n");
    fclose(fp);
}

do_404(char *item, int fd)
{
    FILE    *fp = fdopen(fd,"w");

    fprintf(fp, "HTTP/1.0 404 Not Found\r\n");
    fprintf(fp, "Content-type: text/plain\r\n");
    fprintf(fp, "\r\n");

    fprintf(fp, "The item you requested: %s\r\nis not found\r\n",
            item);
    fclose(fp);
}

/* ------------------------------------------------------ *
 *    the directory listing section
 *       isadir() uses stat, not_exist() uses stat
 *          do_ls runs ls. It should not
 *             ------------------------------------------------------ */

isadir(char *f)
{
    struct stat info;
    return ( stat(f, &info) != -1 && S_ISDIR(info.st_mode) );
}

not_exist(char *f)
{
    struct stat info;
    return( stat(f,&info) == -1 );
}

do_ls(char *dir, int fd)
{
    FILE    *fp ;

    fp = fdopen(fd,"w");
    header(fp, "text/plain");
    fprintf(fp,"\r\n");
    fflush(fp);

    dup2(fd,1);
    dup2(fd,2);
    close(fd);
    execlp("ls","ls","-l",dir,NULL);
    perror(dir);
    exit(1);
}

/* ------------------------------------------------------ *
 *    the cgi stuff.  function to check extension and
 *       one to run the program.
 *          ------------------------------------------------------ */

char * file_type(char *f)
/* returns 'extension' of file */
{
    char    *cp;
    if ( (cp = strrchr(f, '.' )) != NULL )
        return cp+1;
    return "";
}

ends_in_cgi(char *f)
{
    return ( strcmp( file_type(f), "cgi" ) == 0 );
}

do_exec( char *prog, int fd )
{
    FILE    *fp ;

    fp = fdopen(fd,"w");
    header(fp, NULL);
    fflush(fp);
    dup2(fd, 1);
    dup2(fd, 2);
    close(fd);
    execl(prog,prog,NULL);
    perror(prog);
}
/* ------------------------------------------------------ *
 *    do_cat(filename,fd)
 *       sends back contents after a header
 *          ------------------------------------------------------ */

do_cat(char *f, int fd)
{
    char    *extension = file_type(f);
    char    *content = "text/plain";
    FILE    *fpsock, *fpfile;
    int c;

    if ( strcmp(extension,"html") == 0 )
        content = "text/html";
    else if ( strcmp(extension, "gif") == 0 )
        content = "image/gif";
    else if ( strcmp(extension, "jpg") == 0 )
        content = "image/jpeg";
    else if ( strcmp(extension, "jpeg") == 0 )
        content = "image/jpeg";

    fpsock = fdopen(fd, "w");
    fpfile = fopen( f, "r");
    if ( fpsock != NULL && fpfile != NULL )
    {
        header( fpsock, content );
        fprintf(fpsock, "\r\n");
        while( (c = getc(fpfile) ) != EOF )
            putc(c, fpsock);
        fclose(fpfile);
        fclose(fpsock);
    }
    exit(0);
}

int make_server_socket(int portnum)
{
    return make_server_socket_q(portnum, BACKLOG);
}
int make_server_socket_q(int portnum, int backlog)
{
    struct  sockaddr_in   saddr;   /* build our address here */
    struct  hostent     *hp;   /* this is part of our    */
    char    hostname[HOSTLEN];     /* address            */
    int sock_id;           /* the socket             */

    sock_id = socket(PF_INET, SOCK_STREAM, 0);  /* get a socket */
    if ( sock_id == -1 )
        return -1;

    /** build address and bind it to socket **/

    bzero((void *)&saddr, sizeof(saddr));   /* clear out struct     */
    gethostname(hostname, HOSTLEN);         /* where am I ?         */
    hp = gethostbyname(hostname);           /* get info about host  */
    /* fill in host part    */
    bcopy( (void *)hp->h_addr, (void *)&saddr.sin_addr, hp->h_length);
    saddr.sin_port = htons(portnum);        /* fill in socket port  */
    saddr.sin_family = AF_INET ;            /* fill in addr family  */
    if ( bind(sock_id, (struct sockaddr *)&saddr, sizeof(saddr)) != 0 )
        return -1;

    /** arrange for incoming calls **/

    if ( listen(sock_id, backlog) != 0 )
        return -1;
    return sock_id;
}