mkaddr.c

实战Linux socket编程例题源代码

/* mkaddr.c
 *
 * Make a socket address :
 */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

/*
 * Create an AF_INET Address:
 *
 * ARGUMENTS:
 *  1.  addr    Ptr to area
 *              were address is
 *              to be placed.
 *  2.  addrlen Ptr to int that
 *              will hold the final
 *              address length.
 *  3.  str_addr The input string
 *              format hostname, and
 *              port.
 *  4.  protocol The input string
 *              indicating the
 *              protocol being used.
 *              NULL implies "tcp".
 * RETURNS:
 *  0   Success.
 *  -1  Bad host part.
 *  -2  Bad port part.
 *
 * NOTES:
 *  "*" for the host portion of the
 *  address implies INADDR_ANY.
 *
 *  "*" for the port portion will
 *  imply zero for the port (assign
 *  a port number.)
 *
 * EXAMPLES:
 *  "www.lwn.net:80"
 *  "localhost:telnet"
 *  "*:21"
 *  "*:*"
 *  "ftp.redhat.com:ftp"
 *  "sunsite.unc.edu"
 *  "sunsite.unc.edu:*"
 */
int
mkaddr(void *addr,
  int *addrlen,
  char *str_addr,
  char *protocol) {

    char *inp_addr = strdup(str_addr);
    char *host_part = strtok(inp_addr,":");
    char *port_part = strtok(NULL,"\n");
    struct sockaddr_in *ap =
        (struct sockaddr_in *) addr;
    struct hostent *hp = NULL;
    struct servent *sp = NULL;
    char *cp;
    long lv;

    /*
     * Set input defaults :
     */
    if ( !host_part )
        host_part = "*";
    if ( !port_part )
        port_part = "*";
    if ( !protocol )
        protocol = "tcp";

    /*
     * Initialize the address structure :
     */
    memset(ap,0,*addrlen);
    ap->sin_family = AF_INET;
    ap->sin_port = 0;
    ap->sin_addr.s_addr = INADDR_ANY;

    /*
     * Fill in the host address :
     */
    if ( strcmp(host_part,"*") == 0 )
        ;   /* Leave as INADDR_ANY */
    else if ( isdigit(*host_part) ) {
        /*
         * Numeric IP address :
         */
        if ( !inet_aton(host_part,
            &ap->sin_addr) )
            return -1;
    } else {
        /*
         * Assume a host name :
         */
        hp = gethostbyname(
            host_part);
        if ( !hp )
            return -1;
        if ( hp->h_addrtype != AF_INET )
            return -1;
        ap->sin_addr =
            * (struct in_addr *)
            hp->h_addr_list[0];
    }

    /*
     * Process an optional port # :
     */
    if ( !strcmp(port_part,"*") )
        ; /* Leave as wild (zero) */
    else if ( isdigit(*port_part) ) {
        /*
         * Process numeric port # :
         */
        lv = strtol(port_part,&cp,10);
        if ( cp != NULL && *cp )
            return -2;
        if ( lv < 0L || lv >= 32768 )
            return -2;
        ap->sin_port = htons(
            (short)lv);
    } else {
        /*
         * Lookup the service :
         */
        sp = getservbyname(
            port_part,
            protocol);
        if ( !sp )
            return -2;
        ap->sin_port =
            (short) sp->s_port;
    }

    /* Return address length */
    *addrlen = sizeof *ap;

    free(inp_addr);
    return 0;
}