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I am facing a strange issue on my Ubuntu (12.04.3 64 bit). I have a couple of C programs communicating (let's call them sender and receiver programs) through sockets. These work as expected when the machine (a dell laptop in this case) is connected to LAN.

But when I isolate the laptop from the LAN (which means the Wired Connection is disconnected as shown in Network Manager), I can no longer send/receive using sockets. Probably the communication goes through the network card which is not powered (my guess) in this case. Please suggest how to resolve it.

Thanks in advance.

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up vote -1 down vote accepted

You should use loopback address "localhost" or "" in that situation!

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Probably I didn't make it clear in my question, but I am using "multicast communication" using sockets. So I donot need an IP address to send to. – Bhanu Challa Feb 6 '14 at 6:21
Okay, Thats a whole another issue in itself. I don't know much about that but you might look into similar questions about it. A simple google search brings up this…. It basicly tells to use this setsockopt(socket, IPPROTO_IP, IP_MULTICAST_LOOP, 0, 1); – cpz Feb 6 '14 at 6:46
This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. – Maythux Feb 6 '14 at 7:26

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