Sending commands to a Telnet program

[Zach Flynn]

Ok, so I'm programming in Unix if that makes any difference. And I'm
doing:

system("telnet somehost.com 25");

But I can't figure out how to send a command to it. Like, for example,
I would like to send the helo command to the smpt port with this telnet
open. Does anyone here know how to? Thanks.

(kinda desired output)

# ./program

Telnetting...

helo
250 welcome.
mail from: (e-mail address removed)
250 ok.

etc...I think you get the idea that I would like to this inside my C
program.

-Zach

 

[Donovan Rebbechi]

Ok, so I'm programming in Unix if that makes any difference.

Yes, it does. It means that your question is topical in comp.unix.programmer
(but not here).

And I'm doing:

system("telnet somehost.com 25");

But I can't figure out how to send a command to it.

Perhaps it's because you're starting wrong.

Like, for example, I would like to send the helo command to the smpt port
with this telnet open. Does anyone here know how to? Thanks.

start with
man socket
and read the related pages.

Cheers,

 

[Alan Johnson]

Ok, so I'm programming in Unix if that makes any difference. And I'm
doing:

system("telnet somehost.com 25");

But I can't figure out how to send a command to it. Like, for example,
I would like to send the helo command to the smpt port with this telnet
open. Does anyone here know how to? Thanks.

(kinda desired output)

# ./program

Telnetting...

helo
250 welcome.
mail from: (e-mail address removed)
250 ok.

etc...I think you get the idea that I would like to this inside my C
program.

-Zach

First, wrong newsgroup for this.

Second, you'll want to do roughly the following:
1) Open two pipes. (man 2 pipe)
2) Fork. (man 2 fork)
3) Close the unneeded ends of the pipes in each process. (man 2 close)
4) Use dup2 to set stdin and stdout to your pipes. (man 2 dup2)
5) In your child process, do something like execl("/bin/sh", "/bin/sh",
"-c", "telnet host port"). (man 3 execl)

Then you could read from the program and write to its stdin via your
pipes. Or if you were more comfortable, use fdopen to get FILE*'s to
read/write with instead.