#include <stdio.h>
  #include <unistd.h>
  #include <stdlib.h>
  #include <errno.h>
  #include <string.h>
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <sys/socket.h>
  #include <netinet/in.h>
  #include <arpa/inet.h>

  /*
   * This saves lines of code later
   */
  static void
  bail(const char *on_what) {
      perror(on_what);     /* Report error */
      exit(1);            /* Exit Program */
  }

  /*
   * This function accepts as input a socket
   * for which a socket address must be
   * determined for it. Then the address
   * is converted into a string and returned.
   *
   * If an error occurs, NULL is returned.
   */
  char *
  sock_addr(int s,char *buf,size_t bufsiz) {
      int z;            /* Status return code */
      struct sockaddr_in adr_inet;/* AF_INET */

      /*
       * Obtain the address of the socket
       */
socklen_t  len_inet = sizeof adr_inet;
      z = getsockname(s,
          (struct sockaddr *)&adr_inet,
          &len_inet);

      if ( z == -1 )
          return NULL;    /* Failed */

      /*
       * Convert address into a string
       * form that can be displayed
       */
      snprintf(buf,bufsiz,
      "%s:%lu:%u",
          inet_ntoa(adr_inet.sin_addr),
      adr_inet.sin_addr,
          (unsigned)ntohs(adr_inet.sin_port));

      return buf;
  }

  /*
   * Main Program
   */
  int
  main(int argc,char **argv,char **envp) {
      int z;            /* Status return code */
      int sck_inet;                /* Socket  */
      struct sockaddr_in adr_inet;/* AF_INET */
      int len_inet;                /* length  */
      char buf[64];             /* Work buffer */

      /*
       * Create an IPv4 Internet Socket
       */
      sck_inet = socket(AF_INET,SOCK_STREAM,0);

      if ( sck_inet == -1 )
          bail("socket()");

      /*
       * Create an AF_INET address
       */
      memset(&adr_inet,0,sizeof adr_inet);
      adr_inet.sin_family = AF_INET;
      adr_inet.sin_port = htons(0);
      inet_aton("127.0.0.1",&adr_inet.sin_addr);
      len_inet = sizeof adr_inet;

      /*
       * Now bind the address to the socket
       */
      z = bind(sck_inet,
          (struct sockaddr *)&adr_inet,
          len_inet);
      if ( z == -1 )
          bail("bind()");

     /*
      * Now test our sock_addr() function
      */
     if ( !sock_addr(sck_inet,buf,sizeof buf) )
         bail("sock_addr()");

     printf("Address is '%s'\n",buf);

     close(sck_inet);
    return 0;
 }