Telnet: Grabbing Bytes Previously Written During Next Read?

[pbd22]

Hi.

I am building a custom telnet interface and my problem is that I
want to read the user input along with the previously written stream.

Right now I am logging the user.

I have

Login: Bill

Login is written by:

buffer = ASCII.GetBytes( "Login: ");
_clientStream.W rite(buffer, 0, buffer.Length);

Bill is entered by the user.

At the next return, I want to read:

"Login: Bill".

This is how I know its a Login read
and not a Password: read.

I am reading input with the following loop:

Code:
while (true)
{

_bytesRead = 0;
try
{
//blocks until a client sends a message
_bytesRead = _clientStream.R ead(message,
0,4096); //message

}
catch
{
//a socket error has occured
break;
}

if (_bytesRead == 0)
{
break;
}

statusMessage += ASCII.GetString (message, 0,
_bytesRead);
But, my problem is that I get:

"Bill".

when the user submits his string.

How do I get both the written "Login: " and
the read "Bill" on the same read?

Please let me know if i need to provide more information,
otherwsie, thanks a lot for your response!

[Peter Duniho]

On Wed, 16 Jan 2008 12:25:27 -0800, pbd22 <du*****@gmail. comwrote:

Thanks Pete.

I feel a bit thick on this.

That's okay. I know how hard it can be to try to write code on a Monday..
:)

I am still struggling with ClientSate in the switch statement.

Left alone, I get

"ClientStat e is a type but is used like a variable".

That's because you (apparently) do not have a variable named "ClientStat e".

When I do something like

ClientSate state = new ClientState();

Variable name is "state", not "ClientStat e".

or

state = new ClientState();

See above.

and then

switch (ClientState)

the compiler still throws the error.

Sure, it would. If you've named your variable "state" instead of
"ClientStat e", then the switch statement should read "switch (state)"
instead of "switch (ClientState)".

Again, this isn't unique to enums...don't get hung up the fact that it's
an enum. The point of using an enum is that they can be used like a
regular simple value type. So the rules for writing code using enums are
the same as if you were writing code using, for example, an int or a char
or a long, etc.

I'm sorry if using the same name for the variable as the type has confused
things. It's funny...I generally try _not_ to do that, but it's a common
..NET convention for naming properties and public fields. So when I had a
data member of a data structure of type "ClientStat e" in my original
example, I just reused the type name for the name of that data member.
Things seem to have gone downhill from there. :)

Pete

[pbd22]

Hey Peter,

OK, I am starting to get the swing of things, thanks.
The last bit I am having probs with is the 2 substrings.
My current program is going screwy once it connects.
It either hangs, or says your connected after I type each
letter in the Password: field.

I think it has to do with the statusMessage variable.
I think this last bit will do it.

Thanks again.
Peter
public void TheConnectionHa ndler()
{

_telnetSocket = (TcpClient)conn ectionQueue.Deq ueue();
_clientStream = _telnetSocket.G etStream();

buffer = ASCII.GetBytes( "Login: ");
_clientStream.W rite(buffer, 0, buffer.Length);

while (true)
{

_bytesRead = 0;
try
{
//blocks until a client sends a message
_bytesRead = _clientStream.R ead(message,
0,4096); //message

}
catch
{
//a socket error has occured
break;
}

if (_bytesRead == 0)
{
break;
}

statusMessage += ASCII.GetString (message, 0,
_bytesRead);

if (statusMessage. LastIndexOf(END OFLINE) 0)
{

if (currentState != ClientState.Con nected)
{
Login(statusMes sage.Substring( 0,
statusMessage.I ndexOf(ENDOFLIN E)));
//buffer = ASCII.GetBytes( statusMessage);
}
else
{
buffer = ASCII.GetBytes( "You are connected!");
_clientStream.W rite(buffer, 0, buffer.Length);
_clientStream.F lush();

}
}

}

_telnetSocket.C lose();

}

protected void Login(string clientInput)
{

switch (currentState)
{
case ClientState.Log inIDPrompt:
strLoginID = clientInput;
currentState = ClientState.Log inPasswordPromp t;
statusMessage =
statusMessage.R emove(statusMes sage.IndexOf(cl ientInput),
statusMessage.L astIndexOf(clie ntInput)); < --- SHOULD I DO THIS HERE?
//statusMessage = "";
SendPrompt();
break;
case ClientState.Log inPasswordPromp t:
if (CheckPassword( strLoginID, clientInput))
{
currentState = ClientState.Con nected;
}
else
{
currentState = ClientState.Log inIDPrompt;
}
break;
case ClientState.Con nected:
{
break;
}
}

}

private void SendPrompt()
{
buffer = ASCII.GetBytes( "Password: ");
_clientStream.W rite(buffer, 0, buffer.Length);
_clientStream.F lush();

}

public static bool CheckPassword(s tring name, string pass)
{

if (name == "First" && pass == "Last")
{
return true; // just for kicks. remove it.
}
else
{
return false;
}

}

[Peter Duniho]

On Wed, 16 Jan 2008 14:04:23 -0800, pbd22 <du*****@gmail. comwrote:

Hey Peter,

OK, I am starting to get the swing of things, thanks.
The last bit I am having probs with is the 2 substrings.
My current program is going screwy once it connects.
It either hangs, or says your connected after I type each
letter in the Password: field.

I think it has to do with the statusMessage variable.
I think this last bit will do it.

Well, this is related to my suggestion that you only manage the
statusMessage variable from within the method "TheConnectionH andler()".
The code you put in the Login() method to deal with updating the
statusMessage variable is wrong in any case (IndexOf() and LastIndexOf()
in that statement are both returning the same index...nothing 's really
getting removed from the string), but IMHO the code will be easier to
understand and fix if you put that statement in the method dealing with
i/o, rather than the one dealing with login credentials.

IMHO, you should remove the line that attempts to deal with updating the
statusMessage variable from the Login() method. Then the section of code
in TheConnectionHa ndler() that deals with the data after it's been
converted to a string should look more like this:

// You want the first EOL in the string, not the last.
int ichEOL = statusMessage.I ndexOf(ENDOFLIN E);

// If there is an EOL character, then process the current line
if (ichEOL >= 0)
{
// Extract the line of text, up to the EOL (but not including)
string strLine = statusMessage.S ubstring(0, ichEOL++);

// If there are characters after the EOL, set the current
// string to those characters. Otherwise, just reset it to
// an empty string.
if (ichEOL < statusMessage.L ength)
{
statusMessage = statusMessage.S ubstring(ichEOL );
}
else
{
statusMessage = "";
}

if (currentState != ClientState.Con nected)
{
Login(strLine);
}
else
{
buffer = ASCII.GetBytes( "You are connected!");
_clientStream.W rite(buffer, 0, buffer.Length);
_clientStream.F lush();
}
}

Now, all that said, I'll note that you haven't really got a genuine telnet
implementation there. As you saw when dealing with the entering of the
password, data is sent as the user types it. It's not being sent a line
at a time, rather it's being sent a character at a time.

As long as the data is entered without errors, the above should work
fine. But as soon as you have a situation where the user wants to
backspace, you've got a problem. The backspace characters are just going
to get added to the input string, and so of course when the user finally
does send the EOL character, the string up to that point will be messed up.

IMHO, you would be better off refactoring the code so that you've got two
layers: a low-level telnet i/o layer that can deal with backspaces and the
line, and a higher level layer that deals only in complete lines. The
lower level wouldn't present a complete line to the higher level until it
sees an EOL character.

Whether you split the code up like that or not, you definitely need to
include some logic to deal with the user entering backspaces (and possibly
other control characters as well).

Pete

[pbd22]

Pete -

Thanks,

I agree with you about the "character-by-character" implementation.
When I enter my password things get screwy. I need to figure this
out.

Your code sort of worked. I get all sorts of garbage when I get to the
password ("/n") or ("/r") or ("r/n/r"). These are usually before the
actual
password. I think it may have to do with the fact that the ENDOFLINE
variable (that you can't see) is actually

const string ENDOFLINE = "\r\n";

Maybe this is messing things up?

Peter

[pbd22]

Pete -

Thanks,

I agree with you about the "character-by-character" implementation.
When I enter my password things get screwy. I need to figure this
out.

Your code sort of worked. I get all sorts of garbage when I get to the
password ("/n") or ("/r") or ("r/n/r"). These are usually before the
actual
password. I think it may have to do with the fact that the ENDOFLINE
variable (that you can't see) is actually

const string ENDOFLINE = "\r\n";

Maybe this is messing things up?

Peter

[pbd22]

OK,

You are right. I need to figure out how to get the Password line to
react to lines and not characters...

[pbd22]

OK,

You are right. I need to figure out how to get the Password line to
react to lines and not characters...

[Peter Duniho]

On Wed, 16 Jan 2008 15:16:01 -0800, pbd22 <du*****@gmail. comwrote:

[...]
I think it may have to do with the fact that the ENDOFLINE
variable (that you can't see) is actually

const string ENDOFLINE = "\r\n";

Maybe this is messing things up?

Sure, that's definitely going to be part of it. I didn't realize that was
a string instead of a character and the code I posted assumes it's a
single character. That's easy enough to change though. Just change the
"ichEOL + 1" to "ichEOL + EOL.Length".

As you've noted, there are other things you'll need to address as well.
But that should at least fix that issue. :)

Pete

[pbd22]

Thanks Pete.

I am getting there thanks to your help.

I have some nick-knacks that are, it seems,
not that trivial.

1) how do I highlight a line?
2) how do I change background color?
3) how do I change font color?
4) how do I clear the screen (aka. DOS "cls");

For anybody who cares to tackle 'em...

Thanks again for your help,
Peter

[pbd22]

One more to the list for anybody who might know...

1) how do I highlight a line?
2) how do I change background color?
3) how do I change font color?
4) how do I clear the screen (aka. DOS "cls");
5) how to hide password entry (as clear-text or XXXXXXX)?

Thanks again,
Peter