Every device maintains something called an ARP table of IP/MAC address’s that it’s recently communicated with. When a device wants to communicate with another device that’s not in it’s ARP table, it broadcasts locally what is known as an ARP request. If you are the one who uses an Android phone then you will now be able to find the MAC address of your Android device which can then be used for various applications out of which the most one is the Mac filtering. MAC stands for Media Access Control, and, long story short, the MAC address is a code used to identify a particular computer or device on various types of networks, such as Wi-Fi, ethernet, Bluetooth and many more. How to Find Any Device’s IP Address, MAC Address, and Other Network Connection Details Chris Hoffman @chrisbhoffman May 16, 2017, 11:08pm EDT Every network-connected device—computers, smartphones, tablets, smart home gadgets, and more—has an IP address and a unique MAC address that identify it on your network.
I don't really understand why you are trying to do this. 
I Have connected two antena devices through rs232 cable to my system,now i need to get the device MAC Id of two antena device which is connected to my system through rs232 cable. I understand you need to be able to know which antena you are talking to. The vendors manually should give you this information. Either one of two things are happening 1) You have a two serial port (one to each antena) and you just need to asscoiate each antenna to a comm port like com1: and com2: 2) You are using one serial port that is attached to both antena and then there must be a way of configuring the antenna give each one a different device ID. If you give me a vendor webpage, I may be able to figure this out for you. Free photo stitching for mac.
Normally on a PC you can get the mac id by using the followng command ipconfig /all With the antena you are sending commands to the device and the vendor should supply a manual with the least of commands. Look at the least of commands to find out which command gets the device ID or serial number. Then you should be able to send a command on the RS232 interface and retireve the information. What I normally do to test vendors commands is to use a hyperterminal (Programs - Accessories - Communications) before writing any code. Normally commands to devices are ascii.
So you can send the ascii strings with the hyperterminal applcation. I don't really understand why you are trying to do this. I Have connected two antena devices through rs232 cable to my system,now i need to get the device MAC Id of two antena device which is connected to my system through rs232 cable. I understand you need to be able to know which antena you are talking to. The vendors manually should give you this information. Either one of two things are happening 1) You have a two serial port (one to each antena) and you just need to asscoiate each antenna to a comm port like com1: and com2: 2) You are using one serial port that is attached to both antena and then there must be a way of configuring the antenna give each one a different device ID.