#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/time.h>
#include <time.h>  
#include <signal.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>

#define READLEN (128)
void sigalrm(int signal)
{
	fprintf(stderr,"atcmd_response_read timed out.\n");
	exit(-1);
}
void atcmd_response_read(int fd)
{
	int i,count;
	char tmpbuf;
	//alarm(5);
	for (i=0;;i++) {
		count=read(fd,&tmpbuf,1);
		if (count < 0) {
			perror("read failed\n");
			exit(-1);
		}

		if (count == 1 )
		{
			printf("%c",tmpbuf);
			if( i > 2&& (tmpbuf==0xd || tmpbuf==0xa))
				break;
		}
	}
	fflush(stdout);
	alarm(0);
}

void atcmd_write(int fd, char *buf)
{
	ssize_t written=0,retval;
	size_t count=strlen(buf);
	
	while (written < count) {
		retval=write(fd, &buf[written], 1);
		if (retval < 0) {
			perror("write failed\n");
			exit(-1);
		}
		if(retval==1)
			printf("%c",buf[written]);
		written+=retval;
	}
}


double getrand()
{
	int rnd;
	double randfloat;
	rnd=rand();
	return (double)rnd/(double)RAND_MAX;

	
}
int main(int argc,char *argv[])
{
	int fd;
	int count;
	char *devname;
	char tmpbuff[READLEN];
	int  i;
	if (argc != 2) {
		fprintf(stderr,"Usage:\n"
			"randsleep <hso application port>\n");
		return -1;
	}
	devname=argv[1];

	fd=open(devname,O_RDWR);
	if (fd<0) {
		perror("open failed");
		return -1;
	}
	signal(SIGALRM,sigalrm);
	atcmd_write(fd,"ATE0\r\n");
	atcmd_response_read(fd);
	for(i=0;;i++)
	{
		printf("\nLoop %d\n",i);
	        
		atcmd_write(fd,"AT\r\n");
		usleep(getrand()*(double)4000000);
		atcmd_response_read(fd);
		usleep(getrand()*(double)4000000);
	}

}