Post by eddiie on Jul 28, 2008 17:51:10 GMT -5
Hello, I made this post on RetroHackers, thought it might benefit some people here as well:
Ahh is that what it is? Telnet IAC commands (Protocol?) ... I was looking to do this but in reverse. If you use a DOS telnet client to connect to my BBS for example, when I type from the Telnet window, I get double characters echoed back, but if I use the same client and telnet to an Amiga C-Net BBS it seems to compensate for this.
Note, terminal programs work just fine. Its the DOS telnet app that I use and have problems with, even with SecureCRT... I was hoping I could find out how C-Net Amiga compensates and implement it into C-Net 128. It must be a code of some sort? I had no idea about IAC, hopefully this will shed some light on it??
I've tried various switches and stuff when launchnig telnet, but nothing seems to stop the half-duplex type of thing... Any knowledge on this? Thanks!
_________________
Eddie!
Telnet to my C= BBS: bbs.innercirclebbs.com
Port 23 = Centipede, Port 64000 = C-Net 128
=======================================
I found the answer! I think.
Quoted text:
Suppress Go Ahead
The original Telnet implementation defaulted to half duplex operation. This means that data traffic could only go in one direction at a time and specific action is required to indicate the end of traffic in one direction and that traffic may now start in the other direction. [This similar to the use of "roger" and "over" by amateur and CB radio operators.] The specific action is the inclusion of a GA character in the data stream.
Modern links normally allow bi-directional operation and the "suppress go ahead" option is enabled.
Echo
The echo option is enabled, usually by the server, to indicate that the server echos every character it receives. A combination of "suppress go ahead" and "echo" is called character-at-a-time mode meaning that each character is separately transmitted and echoed.
There is an understanding known as kludge-line mode, which means that if either "suppress go ahead" or "echo" is enabled but not both, then Telnet operates in line-at-a-time mode meaning that complete lines are assembled at each end and transmitted in one "go".
End quote.
Microsoft had a good article on it:
support.microsoft.com/kb/231866
Now Im finding out how to construct an IAC command. I love the internet, but sometimes things (the articles, white papers) get too technical for me.
There's a section in that article that says to construct an IAC command you have to the highest bit to 1 or something, getting too complicated, or too technical. Then, further on down it shows some examples and don't know if I can take the 'pseudo code' (?) literally. Guess I will have to test it out and see. For example, "IAC,SB,1" will supress the 'go ahead' thing and get the Telnet client out of half duplex mode. (I'm a**-u-ming) (me)
UPDATE:
After talking with Brain (he might want to add something here like use CHR$(255)CHR$(250)CHR$(1)CHR$(1) - did I get that right? haven't tested it yet), he pointed out the IAC command is CHR$(255).
So I made:
a$=chr$(13)+chr$(255)+"SB,1" and poked a$ to the RS232 buffer, and badabing!! Local echo disabled. However, this is just a hack. To do this properly, it really should be done in the TCP<>Serial program, Brain points out that his TCPSer takes care of this, which is awesome. Leaving only BBS Server. The complicated part is building the correct conversation between the host and telnet app in BBS Server. Which brings up another problem, I can't just blindly send a CHR$(255)+"SB,1".. can I? Maybe I can...
END UPDATE
This is cool, I did something similar when I looked into auto detecting an ANSI, RIPScript, and SuperRes client... I'll tell you how it works I looked at the code in Centipede BBS that had this working, studied it and looked it up: This URL really helped:
www.termsys.demon.co.uk/vtansi.htm
You string all the detect codes together in one spurt then look at the RS232 buffer for a response from the client, if any. Petscii Terms do not respond to such things! So, the trick is to find what codes to send. For ANSI you construct a Device Status query string which is simply ESC[5n ... The client responds with ESC[0n ... Meaning OK, meaning ANSI!
CHR$(27) is the ESC character, BTW.
There is a similar code that is sent the RipScrip terms respond to (now obsolete, pretty much, but still good to know), that code is ESC[! If a RipScript client sees this, it responds "RIPScript version x.xx" or something.
For SuperRES, again, obsolete, but good to know... I could not get this working, but Eric did. This is because it involes the \ key which is an MCI trigger in C-Net... He wound up Poking the ASC values to the RS232 port/buffer/whatever. SuperRes detect is untested. And I am unsure if this is correct.
In Centipede, Adam wrote it:
chr$(13){LINEFEED}{RVS}{SHIFT}p{RVSOFF}@\{TAB}
The CHR$(13) and Linefeed just makes a fresh new line to send it on...
{RVS}{SHIFT}p{RVSOFF} is a reversed text mode shifted 'p' for a capital 'P' in reverse text mode. Not sure what CHR$ that is.
@\ is part of the code...
{TAB} is the CTRL-i character.
But in C-Net it is:
uhh, not in there! hehe Crap, it got left out.
Anyway, you string it all together like so:
a$=chr$(13)+"{LINEFEED}{RVS}{SHIFT}p{RVSOFF}@\{TAB}"+chr$(27)+"[!"+chr$(27)+"[5"+chr$(110)
goto simple sub routine to poke a$ one char at a time to the RS232 buffer, ASC(a$)
Next step is to create a loop to read the RS232 buffer and exit in 2 seconds or if the buffer contains the first unique chracter in a result code, read in CHR$() (the ASCII code). When the buffer contains:
48 = ANSI Detected (chr$(48) is 0) This is the '0' (zero) in the response code ( ESC[0n ) the client's terminal sends from the device status query
82 = RIPScript Detected. (chr$(82) is 'R' in the response code ("RIPScript Version...")
9 = SuperRes (chr$(9) is the TAB character, which is what a SuperRes terminal responds with).
That's pretty much it, clear the buffer before and after this routine too. I'd like to finish this off with turning off the "Go Ahead" mode in a standard telnet client and get this out to all the Sysops out there in BBS land.
you can then set a variable that indicates the terminal type, and use it through out the program to display different files.... Like, if ANSI term, variable set to 1. On a menu read command, add a check: if variable=1 then filename$=filename$+"A". Check if file exists, if not, go back to original filename... This way, the filename+A ("sys.menu 1A" for example) would contain an menu built with ANSI codes. And so on... Problem with this is, you need to find a routine that the BBS uses (IF it has one, C-Net does not currently, but it will) to read a file in the RAW, ie no translation from Petscii to ASCII.
Ok, digging deeper, there's also a problem if the BBS has MCI commands that display variables and such, since this is a RAW file read, it wont go through the MCI piece in the ML. Thus, you can not have a Status screen graphic and then fill that in with the User's name, access level or whatever else you may want. I made a simple fix for this but it is SUPER slow, even with a SCPU. Simple SEQ reader that GET#2,a$... if a$ = < MCI command code > Which is \ in C-Net and Centipede's case), then add to b$ and GET#2,a$ two more times, appending b$, building the three character MCI command, then send that through the regular BBS ML output routine and continue reading the file. Freaking A if it works!! Proof of concept code is:
61000 close2:open2,8,2,"testfile.ans,s,r"
61005 get#2,a$:if st then close 2: goto 1300:rem exits to main menu.
61010 if a$="\" then b$=a$ :forx=1to2 :get#2,a$: b$ = b$ + a$: next: a$=b$: syso: b$="": goto 61005
61015 poke rs232buffer,asc(a$)
61020 goto 61005
I did a lot of this from memory, so I hope it is correct. I will edit if need be.
Good God, where did all this come from? Sorry to go on, hope it helps things in the world.
Anyway, if anyone can help me out with the technical jargan on creating an IAC command, it'd be great. But, it may just be 255,250,1,1 and the 7 bit mumbo jumbo is really the telnet client itself in a lowlevel form.... Now that I typed this up I can get back to testing.
This is good, I been meaning to type all this up. Hope it is ok I did it here.
Thanks,
_________________
Eddie!
Telnet to my C= BBS: bbs.innercirclebbs.com
Port 23 = Centipede, Port 64000 = C-Net 128
