Is the sender on the same computer? Your UDP socket is bound to localhost (127.0.0.1) - if you intend to receive packets from other machines you should bind to one of your local IP addresses or to 0.0.0.0 for “any adapter”.
Make sure that port 8888 is not blocked by a personal firewall on your PC.
You also don’t need WithMulticastLoopback(), that’s only if you use multicast packets, but your socket is not set up to use multicast.