----- Original Message ----- From: Russell Coker <[EMAIL PROTECTED]> To: Chris Wagner <[EMAIL PROTECTED]>; Debian ISP List <[email protected]> Sent: Friday, June 23, 2000 5:18 AM Subject: Re: tcp connection
> On Wed, 21 Jun 2000, Chris Wagner wrote: > >At 02:25 PM 6/20/00 +0200, Russell Coker wrote: > >>They don't use NVT. The TELNET protocol is not running on (for example) a > >>web server. > > > >Yeah but the NVT settings have to be negotiated for each side to talk to > >each other. If I telnet to an Apache webserver on port 80, my telnet is > > No they don't. If the server doesn't start NVT negotiation then nothing > happens. > > >going to negotiate NVT with whatever's on the other end. Both sides have to > >agree to establish the connection. Therefore, either Apache or something > >below Apache in the stack has to know about NVT. Otherwise Apache would > >tell me to go take a flying leap if I tried to telnet to it. What is my > >telnet client negotiating with in this case??? > > Telnet client negotiates nothing. Text you type is sent, but "\n" is > replaced by "\r\n". Text that is received is just displayed as-is. > > As an experiment to find out how hard it would be for you to determine this > without asking the list I timed myself. I determined that in 121 seconds by > running strace(1) on telnet. > I tried using ltrace(1) to determine the same information, but after 149 > seconds I realised that it was not the right tool and would not be able to > provide me with the information. Ltrace displays the values of pointers > instead of the data it referrs to. I could have used "-S" which might have > been more useful, but there's no point when strace(1) is available. > > Then I decided to solve it properly. Firstly I read rfc854 and rfc855 (the > base RFCs on TELNET) which didn't clarify this issue. Then I put a telnet > daemon on port 23 and straced a telnet connection to it. The telnet client > started with sending a sequence of NVT protocol commands to it which were > responded to. Then I put the telnet daemon on port 1000 and repeated the > test, this time the telnet client didn't start sending any NVT commands until > after it had received some (the server had shown itself to be a NVT protocol > server not a web server or whatever else I may have chosen to run on that > port). NVT is totally bi-directional so it could run either way. This took > me 821 seconds. > > Chris, most people here would not be able to do what I just did. However I > believe that you are able to do everything I did (although it may have taken > you a bit longer). I think that you should be answering questions of that > nature not asking them. > > I often see questions that I don't know the answer to, and research them for > the benefit of the person who asked and everyone else on the list. It is a > great way to learn about things if you've got some spare time. This is why I > think that you should have researched and answered if someone else had asked > the question. > > > Russell Coker > > > -- > To UNSUBSCRIBE, email to [EMAIL PROTECTED] > with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED] > >
