We are replacing a "RF modem + Router system" with a Software Defined Receiver. After analyzing the receiving and sent signals we found out that an IPv4 UDP packets have been sent and received. The packets have a source IP like: 220.127.116.11 and the destination IP changes (its sometimes 18.104.22.168 and sometimes broadcast 22.214.171.124) Now the "Software Defined Receiver" is placed inside a PC. As we don't have a router anymore how can we send the obtained IP packets to the destination IP's or broadcast?
You don't need a router to move traffic within the same subnet, that's all layer 2 transport with MAC addresses resolved with ARP.
There are software routers out there-- you could also use a small Linux VM to act as a basic router. You can check out a tutorial here.