Problem with adding physical serial port to vm

Hello

I have ESXi 6.0 on my Supermicro server  and vSphere Management Assistant on ESXi. I connected the serial port of my smart ups to physical port of server, than I added a serial port in Management Assistant. But when I try to communicate from Management Assistant with external devices there is no answer from the serial port. I used other(Cisco console port) serial devices too and I try the same with other(windows) virtual machine too. I didn't receive any answer from serial port. Is there any method  to test the serial port in ESXi?

Thank you for your attention