Hi again, I forgot to say that I'm working with UDP, and all the problem is around this protocol connectionless.
I tried to sniff and redo the "connection start", but always the packages are different but actually, I didn't figured it out completely, and probably I won't studi the OpenVPN protocol deeply right now for that. ngrep: # U 2009/10/29 09:33:07.954515 192.168.9.129:57691 -> 192.168.9.127:1194 8..Rao.T.......... # U 2009/10/29 09:33:07.955865 192.168.9.127:1194 -> 192.168.9.129:57691 @6..............Rao.T..... # U 2009/10/29 09:33:07.956913 192.168.9.129:57691 -> 192.168.9.127:1194 (..Rao.T......6....... the first packet always start with an "8" and has a fixed lenght of 18 characters: 8.....7U.......... 8..XyR............ 8......h.......... but I don't know if I just can send this "info" like a string creating a UDP socket, I tried and it didn't work, maybe some mistake, I can try again. I can't just start an OpenVPN because I don't have the key yet, this verification is done before the OpenVPN connection. I got this from another FORUM: "The trouble with verifying UDP ports as open is that if a UDP port is open, you get no response from it. That's also the case when it's filtered of course. " I understand but not at all, if there is no response, there is no communication.. hehe another manner of how to check if an OpenVPN UDP port is open? Thanks for the answers folks! Lucas. On Wed, Oct 28, 2009 at 6:25 PM, Yevgeny Kosarzhevsky <y...@pisem.net>wrote: > Hi, > > > Lucas Mocellin wrote: > >> Hi all, >> >> briefly: I'm helping in the development of an educational software to >> apply online tests. The client will connect to the server through OpenVPN to >> perform the test. I would like to check if the OpenVPN port is alive and >> accepting connections (check if there is port filtering, and so on.. ). >> >> I'm programming in python. >> >> Does someone know to achieve that? I'm trying to create a socket and send >> any message to the server, but no response, is there any kind of "hello" or >> something like this? >> > > You can test it with netcat utility which is run on the server in listen > mode and on client in client mode. >
