/* xsh_udpeserver.c - xsh_udpeserver */

#include 
#include 
#include 

/*------------------------------------------------------------------------
 * xsh_udpeserver - shell command that acts as a UDP echo server (is
 *                      usually run in background)
 *------------------------------------------------------------------------
 */
shellcmd xsh_udpeserver(int nargs, char *args[])
{
        int32   retval;                 /* Return value from sys calls  */
        uint32  localip;                /* Local IP address             */
        uint32  remip;                  /* Remote sender's IP address   */
        uint16  remport;                /* Remote sender's UDP port     */
        char    buff[1500];             /* Buffer for incoming reply    */
        int32   msglen;                 /* Length of outgoing message   */
        int32   slot;                   /* Slot in UDP table            */
        uint16  echoserverport= 7;      /* Port number for UDP echo     */

        /* For argument '--help', emit a help message   */

        if (nargs == 2 && strncmp(args[1], "--help", 7) == 0) {
                printf("Use: %s\n\n", args[0]);
                printf("Description:\n");
                printf("\tBecome a UDP echo server\n");
                printf("Options:\n");
                printf("\t--help\t display this help and exit\n");
                return 0;
        }

        /* Check for valid IP address argument */

        if (nargs != 1) {
                fprintf(stderr, "%s: no arguments expected\n", args[0]);
                fprintf(stderr, "Try '%s --help' for more information\n",
                                args[0]);
                return 1;
        }

        localip = getlocalip();
        if (localip == SYSERR) {
                fprintf(stderr,
                        "%s: could not obtain a local IP address\n",
                        args[0]);
                return 1;
        }

        /* Register local UDP port */

        slot = udp_register(0, 0, echoserverport);
        if (slot == SYSERR) {
                fprintf(stderr, "%s: could not reserve UDP port %d\n",
                                args[0], echoserverport);
                return 1;
        }

        /* Do forever: read an incoming datagram and send it back */

        while (TRUE) {
                retval = udp_recvaddr(slot, &remip, &remport, buff,
                                                sizeof(buff), 600000);

                if (retval == TIMEOUT) {
                        continue;
                } else if (retval == SYSERR) {
                        fprintf(stderr, "%s: error receiving UDP\n",
                                args[0]);
                        return 1;
                }
                msglen = retval;
                retval = udp_sendto(slot, remip, remport, buff, msglen);
                if (retval == SYSERR) {
                        fprintf(stderr, "%s: udp_sendto failed\n",
                                args[0]);
                        return 1;
                }
        }
        return 0;
}