Linux socket编程之web server

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  256main(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;}

编译webserver.c为web server

cc webserver.c -o webserver

运行并指定端口号5566

./webserver 5566

事先在web server的 统计目录下创建index.html

然后再浏览器中输入：

http://127.0.0.1:5566/index.html

可以看到浏览器中已经显示你的内容了

——————————————————-

两种服务器的设计方法：
DIY——服务器接收请求，自己处理工作。
代理——服务器接收请求，然后创建一个新进程来处理工作。
每种方法的优缺点：
自己做用于快速简单的任务，代理用于慢速的更加复杂的任务，使用SIGCHLD来阻止僵尸（zombie）问题
这里采用的是代理的方法。