On Wed, Apr 8, 2009 at 2:51 PM, David Stevens <dlstevens@xxxxxxxxxx> wrote: > Matt Garman <matthew.garman@xxxxxxxxx> wrote on 04/08/2009 11:43:48 AM: > >> Is it a dangerous oversimplification to think of the port as simply an >> extension of the address? E.g., you have address 239.0.0.1 port 1234, >> but just call it 239.0.0.1.1234. Then you can tell at a glance that >> it will result in a different socket than 239.0.0.2.1234 (i.e. address >> 239.0.0.2 port 1234). [I'm not suggesting using this nomenclature, it >> just seems like an intuitive way to think about/explain it.] > > That is correct. I just did a test, and don't understand the results. I wrote two simple programs, one each for sending and receiving multicast data. I'm running all programs on the same machine: I start the sender program, sending on address 239.1.1.100 port 10000. I start the receiver program using the same address+port as the sender. I see data. I kill then restart the receiver program using a different address, same port: no data. I kill then restart the receiver program using the same address, different port: no data. I start a receiver with a different port, same address: no data. I leave that receiver running, and start a second receiver with the same address+port as the sender: I get data. The first receiver still doesn't see any data. So far so good, exactly what I expected. But now it gets weird: I start a receiver with the same port, but a different IP. No data. I leave that receiver running, and start a second with the same address+port as the sender: I get data on this program, *and start getting data on the first program*. If I kill the second receiver, I stop getting data on the original receiver. Any thoughts? Thanks, Matt -- To unsubscribe from this list: send the line "unsubscribe linux-net" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
