88E1111 Marvell PHY Chip Clock

Do you see the RX light on the PC? If not, then the Ethernet packet is somehow malformed. Check your transmitted Ethernet and UDP headers, the Ethernet packet checksum and UDP packet data checksum. If you don't see the RX light, I'd suspect the Enet header or checksum. Note that you can't rule out malformed Ethernet packets if you see the light. Some PCs blink the light even if malformed packets are sent. If your packets are malformed, they may be discarded by the OS before being sent to wireshark.