How to send UDP packet if the system has multiple network cards?

You need to send a UDP packet to a device connected to my workstation via Ethernet. The difficulty is that this device only supports a limited network stack, in particular no support for ARP.
To work around this limitation I expect using the manually add entry in ARP cache(arp -s ).

The system has multiple network card, how the OS determines which one will be sent a UDP packet?
As of Python to send UDP-packages with I need network card?
March 12th 20 at 08:07
1 answer
March 12th 20 at 08:09
the routing table contains all necessary information

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