Determining the IP address of neighbors in a wireless mesh

Question

I am attempting to create a program for a wireless mesh (adhoc in all but name). Most of the network will deal with TCP messaging but to determine all neighbor IPs (as they will be unknown on startup), I choose to use UDP Broadcast for the initial discovery messages.

I have two problems currently. First, the UDP Broadcast is only being received by the sender and none of its neighbors; second, as the receiving socket can not accept the sender's socket (due to the message being a datagram), I am not able to recover an IP address.

I am in need of a methodology that would allow this to work.

score 3 · Accepted Answer · edited May 23 '17 at 11:56

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You're supposed to get the source address along with the datagram via e.g. recvfrom. Here's the .NET version. You also have to set a socket option to send broadcast datagrams.

See also this question: Broadcasting UDP thru all network cards

edited May 23 '17 at 11:56

Community

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answered Nov 10 '10 at 03:21

Ben Voigt

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Thanks, that fixed the second issue. – Scott S Nov 10 '10 at 03:38
You set the broadcast option, and still can't send a datagram to multiple nodes? – Ben Voigt Nov 10 '10 at 19:53
They were, I had the system parsing them wrong so they weren't showing up as received. Took a while to figure out because no errors or exceptions were showing up anywhere. – Scott S Nov 11 '10 at 20:12

score 0 · Answer 2 · answered Nov 10 '10 at 03:20

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Why UDP and why not say, ICMP Pings to the broadcast address, or even bruteforcing your way down the netblock with ICMP pings? It seems to me that a ping would be more appropriate for determining if a specific host is "alive", no?

answered Nov 10 '10 at 03:20

Douglas Muth

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Most systems are locked down and only reply to unicast pings. – Ben Voigt Nov 10 '10 at 03:21

Determining the IP address of neighbors in a wireless mesh

2 Answers2