Saturday, April 24, 2010

nmap 1

got a program called nmap, using the windows gui.

i can't really get a port scan to work on another computer. i tried to get jingping to turn off her firewall, but she said it was already off - i guess norton does its own firewall.

still, nmap has other neat functions. you can get it to do traceroute for you, along with other things, and it will hold on to all the data for you. as you do this, it creates a graphic plot of all the addresses you've been querying. if you're doing tracerouts, it plots ip paths, which is fantastic. here's what i did:

still working off the mysteries of Skype, i ran the network monitor for a few minutes, and got a list of those UDP conversations through port 34368. most of these just consist of my computer sending out a single datagram to some other address, with which i may or may not be also involved in a TCP session. a few ms later, i get a UDP back from the target. there were about 15 of these over a 5 minute period. i plugged them all into the nmap and tracerouted them (had to do this one by one, i'm going to have to get a little more sophisticated), and got back a neat plot showing how all these connections are related to me. these other IP addresses were all over the world, China, NZ, Japan, Russia, France, all over. maybe those are the supernodes, and i'm just registering with them by sending a datagram?

the plot is interesting in itself:

you can't read them but the ip address of every node along the route is listed. the maps are dynamic; you can highlight a node and all its children (those further down the route away from the center), change the center node, rotate, etc.

like i said, most of those UDP exchanges were just 2 packets, one out and one response. there were two other things that happened. one was, I sent 2 UDP packets and got back 1 RTP packet, which i think is actually a UDP packet carrying audio/video information. there wasn't anything else associated with that address, though, so i can't guess what that was about.

the other interesting thing was an instance where i sent 3 UDP packets to a certain address, with no response. i actually guessed the reason: they were being sent to jingping's laptop on campus, on the UofL wireless network, where it hasn't actually been connnected since early friday evening: i sent those UDP packets after midnight, more than 7 hours after she had disconnected.

why did this happen? one thing is, i may have left Skype running on the computer in my office, and during the day that was a connection to her laptop on the campus wireless network. or, i may have turned it off - sometimes i forget, usually i don't, but i don't usually remember if i remembered, only if i forgot (strange how that works). at any rate, for some reason, my computer, being connected with my Skype account, thought to check to see if that UofL address was still on, despite the fact that the account it had been associated with was now associated with another IP address. this doesn't make a lot of sense to me. some sort of cleanup work on Skype's part?

mysteries, mysteries.

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