C / C++ / MFC

15-Sep-05 23:03

Does anybody know of a good technique to detect if a TCP-port is open on a server, without fully connecting to it? I need to do a half-way TCP-connect, so that the server's accept() isn't executed. The server becomes quite "upset" if I just connect and disconnect, not adhering to its protocol. The protocol is proprietary, and I do not have the source code for the server, so I can't add my own tweaks to it. Hence I need to "fool" it on TCP-level.

I know there are implementations such as NMap out there, but I figured I'd ask here for the basic techniques first, before taking a plunge into complex multiplatform sources.

Note: I'm no dummy, so you don't have to give me tons of source code. Some hints would do just fine.

ps. I wouldn't be offended, should you give me code Big Grin | :-D

--
An eye for an eye will only make the world blind.

Anonymous16-Sep-05 0:21

Anonymous

16-Sep-05 0:21

I took print out of your query and went to desks of TCP experts , The answers
1) Call lsof on unix flavoured OSs
2) net stat -p tcp (u can use the rexec(IP , Cmd ) to execute this command at the remote server , but i am not sure of rights issues of RPC )
3) Ethreal tool can help (but u r searching for code ..almost useless)

P.S : not sure of the rexec() function name . Which OS u r talkign abt ?

Jörgen Sigvardsson16-Sep-05 0:53

16-Sep-05 0:53

I thought it was obvious that I'm talking about Windows, especially considering the fact that this message board is called "Visual C++". Smile | :)

Anyway, I need to do it programatically, so I can't just launch a second process, or make it a manual operation for the end user to do.

dharani16-Sep-05 0:23

dharani

16-Sep-05 0:23

In fact I replied to your message (but shows "Ananymous" as I di dnot log in while replying)

redindian

dharani16-Sep-05 0:27

dharani

16-Sep-05 0:27

As you know the server IP + port ,you can filter the netstat -p command's results and find if the port is established or not . Right ?

redindian

Jörgen Sigvardsson16-Sep-05 0:56

16-Sep-05 0:56

I don't want to establish a connection - it confuses the server, because I don't follow the protocol. I just want to detect the presence of an open port on a particular IP address.

I've found the TCP state charts, and it seems that all I need to do is to send a TCP/SYN-message, and wait for a TCP/SYN_ACK message. Then I know there is a process listening on that port. Then my plan is to send a TCP/RST to reset that connection sequence, thus preventing the server from acquiring a socket.

HumanOsc16-Sep-05 1:17

HumanOsc

16-Sep-05 1:17

Hello...

Look at:

http://www.codeproject.com/internet/NagTPortScanner.asp[^]

Not very good explained but a smart introducion about TCP SYN scanning... #

Best regards... Smile | :)

Jörgen Sigvardsson16-Sep-05 1:23

16-Sep-05 1:23

Thank you for that link! Unfortunately it makes use of win/libpcap, which has a rather fascist license requirement, which states I must reproduce the copyright information. :grumble:

It's on my list though, in case I don't find something else. So, once again, thank you!

looking for some codes for voip dialer

HumanOsc16-Sep-05 2:57

HumanOsc

16-Sep-05 2:57

Hello again...

Look at:

http://www.c-schell.de/home/cpp/source/gull.c[^]

This an example in pure c...
I believe this can be helpful for your problem, too...

Sadibd15-Sep-05 21:45

Sadibd

15-Sep-05 21:45

I m planning to write a Voip dialer that can be used as net 2 phone dialer. Can any one provide me any kind of source code for this?

Urgent ....How to Remove Help button from CPropertysheet

snprani15-Sep-05 21:44

snprani

15-Sep-05 21:44

Hi,

How to Remove Help button from CPropertysheet. i have tried in this way, but no result. help me in this regard. Urgent.............

sheet.m_psh.dwFlags &= ~PSH_HASHELP;
page1.m_psp.dwFlags &= ~PSH_HASHELP;
page2.m_psp.dwFlags &= ~PSH_HASHELP;
page3.m_psp.dwFlags &= ~PSH_HASHELP;
page4.m_psp.dwFlags &= ~PSH_HASHELP;

sheet.DoModal();

it is still appearing.

bye

Re: Urgent ....How to Remove Help button from CPropertysheet

prasad_som15-Sep-05 23:27

prasad_som

15-Sep-05 23:27

this page has information about removing help button.
You need to write a callback
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/shellcc/platform/commctls/propsheet/propsheet.asp[^]

HTTP endrequest problem

Sonani Prakash15-Sep-05 21:33

Sonani Prakash

15-Sep-05 21:33

Hi I am having problem about EndRequest()function of class CHttpFile Function.it is
taking too much time to execute..Instead of that if i am using Win
APIs it is running ok...
I am getting response but is taking much time that is the main problem
it takes apprx. 1 min.
So Can any body suggest me what can be the problem..?

sonani prakash

small help

radesh15-Sep-05 20:57

radesh

15-Sep-05 20:57

hello a small question,

given a handle to a window, is it possible to determine which type of window it is? like combobox or listbox or editbox e.t.c. and how to type cast the CWnd object for that handle into its corresponding class's object.

Re: small help

Steen Krogsgaard15-Sep-05 21:13

Steen Krogsgaard

15-Sep-05 21:13

You can get the class name from GetClassName. Then you can cast your CWnd to the appropriate derived class.

Cheers
Steen.

"To claim that computer games influence children is ridiculous. If Pacman had influenced children born in the 80'ies we would see a lot of youngsters running around in dark rooms eating pills while listening to monotonous music"

Re: small help

tejaswi-teja17-Sep-05 22:35

tejaswi-teja

17-Sep-05 22:35

Thank you very much.

random number...

Raza568015-Sep-05 20:26

Raza5680

15-Sep-05 20:26

a simple question...
how to generate random numbers by rand() within a given range...
let say between 20 and 40
thanks

Re: random number...

Bob Stanneveld15-Sep-05 20:36

Bob Stanneveld

15-Sep-05 20:36

Hello,

Does:

srand( (unsigned)time( NULL ) );
int nNumberBetween20And40 = (rand() % 20) + 20;

(rand() % 20) gives you a number between 0 and 20.

Behind every great black man...
... is the police. - Conspiracy brother

Blog[^]

Need an API for getting FDQN of a machine.

shiva e balasubramaniam15-Sep-05 20:15

shiva e balasubramaniam

15-Sep-05 20:15

I need to get a fully qualified name of the host machine.(Eg: Shivaeb.invent.co.in)
I tried using gethostname() API, but it is returning only the machine name(Eg:Shivaeb) not the fdqn name(Shivaeb.invent.co.in).

Could any one suggest any API or any logic to get the fully qualified name of the PC?.

Thanks & Regards,
Shiva

prasad_som15-Sep-05 21:20

prasad_som

15-Sep-05 21:20

use this code

char ah[100]={0};
gethostname(ah,100);
hostent* kk=NULL;
kk=gethostbyname(ah);
//now access h_name of hostent(kk)

shiva e balasubramaniam16-Sep-05 2:53

shiva e balasubramaniam

16-Sep-05 2:53

Thank you for your reply.
I tried with that code but what is happening is even hostent h_name member is also having the same hostname as returned by gethostname() API.

There is one more API getnameinfo(), which this also i could not get the fully qualified name of the host machine.

Could you please suggest me some other solutions?.

Thanks & Regards,
Shiva

prasad_som16-Sep-05 3:14

prasad_som

16-Sep-05 3:14

Shiva,
I wonder how it is not working. I've tested code on my m/c.
see description of hostent on MSDN, too.
h_name
Official name of the host (PC).If using the DNS or similar resolution system, it is the Fully Qualified Domain Name (FQDN) that caused the server to return a reply. If using a local “hosts” file, it is the first entry after the IP address.
I've given up.

leaving for the day and weekend. Happy ganesh chaturthi

-- modified at 9:36 Friday 16th September, 2005