void recv_file(int sk)
{
    char incmsg[CMSG_SPACE(sizeof(_sctp_cmsg_data_t))];
	struct iovec iov;
	struct msghdr inmessage;
    struct cmsghdr *cmsg;
    _sctp_cmsg_data_t *sinfo;
	int error;
    static char buffer[1024];
    int buffer_size=1024;
    int check_listen;

 	/* Mark sk as being able to accept new associations */
	check_listen = listen(sk, 5);
	if (check_listen != 0) {
		printf("\n\n\t\tlisten Failure:  %s.\n\n\n",
		       strerror(errno));
		exit(1);
	}
	/* Initialize inmessage with enough space for DATA... */
	memset(&inmessage, 0, sizeof(inmessage));
	if ((iov.iov_base = malloc(5000)) == NULL) {
		printf(" Can't allocate memory.\n");
		exit(1);
	}
	iov.iov_base = buffer;
	iov.iov_len = 5000;
    inmessage.msg_iov = &iov;
	inmessage.msg_iovlen = 1;
	/* or a control message.  */
	inmessage.msg_control = incmsg;
	inmessage.msg_controllen = sizeof(incmsg);
    int writebyte=0;
    int fd[10];
     int check_file=0;
    for(check_file=0;check_file<count_file;check_file++)
    {
        fd[check_file] = fopen(localfile[check_file],"w");
        if(fd[check_file]==-1)
            return;
    }
	printf(" listening...\n");
	/* Get the messages sent */
    int time_clock=0;
    time_t start, finish;
    clock_t start_c, finish_c;
	long duration=0;
    double duration_c=0;
    long temp;
	while ((error = recvmsg(sk, &inmessage, MSG_WAITALL))>=0) {
        if( !(inmessage.msg_flags & MSG_NOTIFICATION )){
            cmsg = CMSG_FIRSTHDR(&inmessage);
            if(cmsg==NULL)continue;
            sinfo = (struct sctp_sndrcvinfo*)CMSG_DATA(cmsg);
            writebyte=fwrite(buffer,error,1,fd[sinfo->sinfo_stream]);
            if(time_clock==0)
                {
                    time_clock=1;
                    start=time(NULL);
                    start_c=clock();
                }
        }
		else {
			union sctp_notification *sn;
			sn = (union sctp_notification *)iov.iov_base;
			if ((sn->sn_header.sn_type == SCTP_ASSOC_CHANGE) &&
			    (sn->sn_assoc_change.sac_state
			     == SCTP_SHUTDOWN_COMP))
                             break;
                    }

        }
    finish=time(NULL);
    finish_c=clock();
    temp=finish_c-start_c;
    duration_c=(double)temp/CLOCKS_PER_SEC;
    duration=finish-start;
	printf("the file has been transferred in %d secs and %2.3f secs.\n",duration,duration_c);
	close(fd);
         close(sk);
} /* command_listen() */