Making a list of distinct IPs broadcasting UDP

Hello, good day!

    I have managed to create a very simple UDP sending and receiving script to send and receive messages from a specified multicast group.. the game we are creating listens on one port and sends through another port (2013 and 2013).. 

    There is no problem if there is only one game creator, the ip is being stored in a List<> but when another player creates a game, the List<> goes filled up very fast and my "check if there is the same ip on the list already" code fails and unity crashes.. dunno if the receive is too fast or somthing

     Btw, I'm using UDPClient and multihreading
     Thanks for those who will spare their precious time,


                                                                                -Jece