Bound dual-network port device communication: Packet Recognition

Communication between the bound dual-network port device: Packet recognition-Linux general technology-Linux programming and kernel information. For details, see the following. An embedded device with two network ports on it. I bound them to one for use and communicated with the server for multicast. The multicast address is 227. 0. 0. 1.
When both network ports are connected, the server sends multicast data. When the device receives multicast data packets, it receives two identical data packets and then sends two responses to the server.
Unplugging a network port, the server sends a packet multicast data, and the device can only receive one packet, but cannot send a response packet normally,
The server sends two messages. The device receives two messages but only replies one. The number of packets received by the device is the same as that sent by the server,
However, the number of response packets sent from the device to the server is halved !!!
The reason may be that, after binding, the network port Server Load balancer sends one port, and the network port that is not connected to the network cable is also sent.
I want to know how to determine from which network port the data is received after the two network ports are bound, and how can I send data from that network port?
I hope you can help me and give me some suggestions .... Thank you !!!!!