พอดีเค้าบอกว่าตัวนี้เป็น API ให้วางไว้บน Server ผมก้อยัง งง งง อยู่ ไม่ค่อยรู้ตัวภาษา C เท่าไหร่ เลยอยากทราบรายละเอียดหน่อยอะครับ ใครพออธิบายให้ได้บาง ว่าต้องใส่อะไร หรือปรับแก้ตรงไหน
/*##### auth.c listing*/
/*##### Authentication Script Example -- Start --*/
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include<netinet/in.h>
#include<getopt.h>

char *command, *ipaddr, *macaddr;
char *name, *password, *role;
char *tout, *secret;
char *auth, *key, enchashbuf[41];
unsigned char hashbuf[20];
char *version;
char post[4096], cmdbuf[512], encbuf[1024];
#define DEBUG
#ifdef DEBUG
#define debug(x...)fprintf(stderr, x)
#else
#define debug(x...)
#endif

extern int cgi_escape_url(char *t, int tl, char *s, int sl, int b_newline);
static void encode_message_digest (unsigned char *md, int mdlen, char *output);

static void usage (void)
{
    fprintf(stderr, "Usage: ecp [options] <switch> <command> [<secret>]\n");
    fprintf(stderr, " \n");
    fprintf(stderr, " <switch> Switch IP address.\n");
    fprintf(stderr, " <command> One of add, del, or authenticate.\n");
    fprintf(stderr, " <secret> Shared secret.\n");
    fprintf(stderr, " \n");
    fprintf(stderr, " -i ipaddr User IP address in A.B.C.D format.\n");
    fprintf(stderr, " -m macaddr User MAC address in aa:bb:cc:dd:ee:ff format.\n");
    fprintf(stderr, " -n name User name.\n");
    fprintf(stderr, " -p passwd User password.\n");
    fprintf(stderr, " -r role User role.\n");
    fprintf(stderr, " -t timeout User session timeout.\n");
    fprintf(stderr, " -v version API version number. Default is 1.0\n");
    fprintf(stderr, " -a method one of md5, sha-1 or cleartext.\n");

    exit(1);
}
main(int argc, char **argv)
{
    char c, *p;
    int fd, len, postlen;
    struct sockaddr_in sa;
    while ((c = getopt(argc, argv, "a:i:m:n:p:r:t:v:")) != EOF) switch(c) {
    case 'i':/* ipaddr */
        ipaddr = optarg;
        break;
    case 'm':/* macaddr */
        macaddr = optarg;
        break;
    case 'n':/* name */
        name = optarg;
        break;
    case 'p':/* password */
        password = optarg;
        break;
    case 'r':/* role */
        role = optarg;
        break;
    case 't':/* session timeout */
        tout = optarg;
        break;
    case 'v':/* version */
        version = optarg;
        break;
    case 'a':/* authentication */
        auth = optarg;
        if (!strcasecmp(auth, "sha-1") &&
            !strcasecmp(auth, "md5"))
            usage();
        break;
    default:
        usage();
        break;
    }
    argc -= (optind - 1);
    argv += (optind - 1);
    if ((argc < 3)) {
        usage();
    }
    if (version == NULL)
        version = "1.0";
    debug("server=%s, command=%s, version=%s, secret=%s\n",
        argv[1], argv[2], version, argv[3]?argv[3]:"<>");
    if (argv[3]) secret = argv[3];
    p = cmdbuf;
    sprintf(p, "xml=<aruba command=‘%s’>", argv[2]);
    p += strlen(p);
    if (ipaddr) {
        sprintf(p, "<ipaddr>%s</ipaddr>", ipaddr);
        p += strlen(p);
    }
    if (macaddr) {
        sprintf(p, "<macaddr>%s</macaddr>", macaddr);
        p += strlen(p);
    }
    if (name) {
        sprintf(p, "<name>%s</name>", name);
        p += strlen(p);
    }
    if (password) {
        sprintf(p, "<password>%s</password>", password);
        p += strlen(p);
    }
    if (role) {
        sprintf(p, "<role>%s</role>", role);
        p += strlen(p);
    }
    if (tout) {
        sprintf(p, "<session timeout>%s</session timeout>", tout);
        p += strlen(p);
    }
    if (secret) {
        if (auth == NULL) {
            key = secret;
            auth = "cleartext";
#ifndef OPENSSL_NO_SHA1
        } else if (!strcasecmp(auth, "sha-1")) {
            key = enchashbuf;
            SHA1(secret, strlen(secret), hashbuf);
            encode_message_digest(hashbuf, 20, enchashbuf);
#endif
        } else if (!strcasecmp(auth, "md5")) {
            key = enchashbuf;
            md5_calc(hashbuf, secret, strlen(secret));
            encode_message_digest(hashbuf, 16, enchashbuf);
        }
        debug("Message authentication is %s (%s)\n", auth, key);
        sprintf(p, "<authentication>%s</authentication><key>%s</key>",
            auth, key);
        p += strlen(p);
    }
    debug("\n");
    sprintf(p, "<version>%s</version>", version);
    sprintf(p, "</authresponse>");
    cgi_escape_url(encbuf, sizeof(encbuf), cmdbuf, strlen(cmdbuf), 0);

    postlen = sprintf(post,
        "POST /auth/command.xml HTTP/1.0\r\n"
        "User-Agent: ecp\r\n"
        "Host: %s\r\n"
        "Pragma: no-cache\r\n"
        "Content-Length: %d\r\n"
        /* "Content-Type: application/x-www-form-urlencoded\r\n" */
        "Content-Type: application/xml\r\n"
        "\r\n"
        "%s",
        argv[1], strlen(encbuf), encbuf);

    inet_aton(argv[1], &sa.sin_addr);
    sa.sin_family = AF_INET;
    sa.sin_port = htons(80);
    fd = socket(AF_INET, SOCK_STREAM, 0);
    if (fd < 0) {
        perror("socket");
        exit(1);
    }
    if (connect(fd, (struct sockaddr *) &sa, sizeof(sa)) < 0) {
        perror("connect");
        exit(1);
    }
    if (write(fd, post, postlen) != postlen) {
        perror("write");
        exit(1);
    }
    while ((len = read(fd, post, sizeof(post))) > 0)
        write(1, post, len);
    close(fd);
    exit(0);
}
static void encode_message_digest (unsigned char *md, int mdlen, char *output)
{
    int i;
    for (i=0; i<mdlen; i++) {
        sprintf(output, "x", md);
        output += 2;
    }
}