A simple google search of communicating in C# using UDP would have resolved your issue.
UdpClient Class (System.Net.Sockets)[
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c# - Simple UDP example to send and receive data from same socket - Stack Overflow[
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Google[
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Unless you have some code you've actually tried and gotten stuck somewhere, i suggest you start with the above links, do some work on your end (not expect us to do the work for you) and see if you can massage these examples to meet your needs.
Should you actually attempt to solve your issue on your own and get stuck somewhere, feel free to come back with a clear explanation of your issue and any relevant code samples and I am sure you will get more meaningful help.