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There is quite a few examples to RECEIVE multicast messages with a spcific network interface (NIC, e.g. eth0, 127.0.0.1 etc). However, there is few discussion/examples about how to SEND multicast (UDP) messages to a specific interface, e.g. local loop (127.0.0.1) instead of eth0 by default.

Background: RedHat Linux, Python, 224.1.1.1 5005

Python Code example in Multicast in Python

A similar discuss for IPv6 How to send multicast packets via a specfic interface in Linux

A similar discuss for Windows How to Multicast (send) to first NIC?

Thanks in advance.

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1 Answer 1

Reset to default
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The question that you've linked How to Multicast (send) to first NIC? mentions that you could use IP_MULTICAST_IF:

sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_IF, socket.inet_aton(addr))
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3 Comments

Don't forget to increase TTL
@e271p314: I don't remember what it is about but the code example that is linked in the question appears to handle TTL already (since 2009). My answer sets a single option i.e., it only answers the question in the title.
First of all, thanks a lot, your answer is correct. when I tried it I saw I didn't get the multicast and was breaking my head to understand what is the issue. My TTL was configured to 2 because I copy pasted the code. After some time I realized from this link That I need to "Increase to reach other networks" So I just though that if might be usful to other which came to your answer get this tip too :-)

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