xsh_udpserver.c

Go to the documentation of this file.

/* xsh_udpeserver.c - xsh_udpeserver */

#include <xinu.h>
#include <stdio.h>
#include <string.h>

/*------------------------------------------------------------------------
 * 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;
}