Reading and writing from/to ttyS0 - c

Question

I have a RPI Zero W connected to my virtual machine through USB, which can be found under /dev/ttyS0 on both PC and the RPI. Currently I am trying to send something from the RPI through the USB cable to the virtual machine (PC).
I am trying to read on the port with the following code:
#include <stdio.h> /* Standard input/output definitions */
#include <string.h> /* String function definitions */
#include <unistd.h> /* UNIX standard function definitions */
#include <fcntl.h> /* File control definitions */
#include <errno.h> /* Error number definitions */
#include <termios.h> /* POSIX terminal control definitions */
/* * 'open_port()' − Open serial port 1. *
* Returns the file descriptor on success or −1 on error. */
int fd; /* File descriptor for the port */
int open_port(void)
{
fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);
if(fd == -1)
{
/* * Could not open the port. */
perror("open_port: Unable to open /dev/ttyS0 − ");
}
else
fcntl(fd, F_SETFL, FNDELAY);
return (fd);
}
int close_port(void)
{
close(fd);
return (fd);
}
int main()
{
printf("Serial reader has started...\n\n");
while(1)
{
open_port();
close_port();
}
return 0;
}
and on the RPI side, I have made a little bash script, which sends the character 1:
while :
do
echo "sending character 1 to /dev/ttyS0"
echo "1" > /dev/ttyS0
done
However, even though the bash script and the c program are both running in continuous loops, I am not receiving anything on the PC side.
What could be the reason?