Calling newlisp from Javascript

Started by abbat, November 03, 2009, 12:44:53 PM

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abbat

November 03, 2009, 12:44:53 PM Last Edit: December 31, 1969, 04:00:00 PM by Guest
I use newLISP as local http server on Windows platform:

  newlisp.exe -c -d 1235



It is possible send some string (like "(+ 2 3)") from Javascript to newLISP session

for evaluate and get back answer?

cormullion

#1
November 03, 2009, 02:08:27 PM Last Edit: December 31, 1969, 04:00:00 PM by Guest
Don't know. Wouldn't that be a security problem?

Lutz

#2
November 03, 2009, 08:40:41 PM Last Edit: December 31, 1969, 04:00:00 PM by Guest
It should be possible to do this from JavaScript. Connect to port 1235 and send the string "(+ 3 4)n",  then wait for an answer which should be "7n" (7 plus line-feed). And yes, there is a big potential for security problems; so carefully check each string received for evaluation.

abbat

#3
November 04, 2009, 08:12:30 AM Last Edit: December 31, 1969, 04:00:00 PM by Guest
Thanks you for reply.

I am beginner in newLisp and Javascritp.

Please, give me an example.

I try run newlisp:

  newlisp.exe. -c -d 8080

and open in browser this document:

 
Code Select

<html>
<body>
<h3>newLISP server and JS demo</h3>

<script type="text/javascript" language="javascript">

if (window.XMLHttpRequest) {
    xmlHttp = new XMLHttpRequest();
} else if (window.ActiveXObject) {
    xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}

function newLispEval(expr) {
  xmlHttp.open("GET", "http://localhost:8080", false);
  try {
    xmlHttp.send(expr);
  } catch (e) { alert(e.message); }
  return xmlHttp.responseText;
}

var answer = newLispEval("(+ 3 4)n");

document.write(answer);
document.write("<BR>ok.");
</script>
</body>
</html>
<!-- end of file -->


but get NS_ERROR_FAILURE for "xmlHttp.send(expr);"

abbat

#4
November 04, 2009, 08:13:54 AM Last Edit: December 31, 1969, 04:00:00 PM by Guest
Sorry, misprint:

I run newLISP with line:

newlisp.exe -c -d

abbat

#5
November 04, 2009, 08:14:58 AM Last Edit: December 31, 1969, 04:00:00 PM by Guest
Sorry again :)

newlisp.exe -c -d 8080

Lutz

#6
November 04, 2009, 09:49:57 AM Last Edit: December 31, 1969, 04:00:00 PM by Guest
newLISP when started: newlisp -c -d 8080, answers to two different protocols. What I was demonstrating is the simple command line protocol, but  xmlHttp.open() is using the HTTP protocol.



So with: newlisp -c -d 8080, the newLISP server handles the HTTP protocol too. But you would need to initiate some kind of CGI process and pass the expression to evaluate as a parameter in a GET or POST request.



Cormullion is doing this here:



http://unbalanced-parentheses.nfshost.com/lambdalator/index">http://unbalanced-parentheses.nfshost.c ... ator/index">http://unbalanced-parentheses.nfshost.com/lambdalator/index



If your emphasis is on asynchronous update then look at this example:



http://www.newlisp.org/index.cgi?page=AJAX_and_newLISP">http://www.newlisp.org/index.cgi?page=AJAX_and_newLISP



You could merge both approaches passing the expression to evaluate as parameter in the xmlHttp GET request.

abbat

#7
November 07, 2009, 09:17:22 AM Last Edit: December 31, 1969, 04:00:00 PM by Guest
Sorry for long silent.



I create file "eval.cgi":
Code Select

#!/usr/bin/newlisp

(define (url-translate str)
   (replace "%([0-9A-F][0-9A-F])" str (format "%c" (int (append "0x" $1))) 1))

(print "Content-type: text/htmlrnrn")
(print (eval-string (url-translate (env "QUERY_STRING"))))
(exit)

# end of file


and file "test1.html":
Code Select

<html>
<body>
<h3>newLISP server and JS demo</h3>

<script type="text/javascript" language="javascript">

if (window.XMLHttpRequest) {
    xmlHttp = new XMLHttpRequest();
} else if (window.ActiveXObject) {
    xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}

function newLispEval(expr) {
  xmlHttp.open("GET", "eval.cgi?" + expr, false);
  try {
    xmlHttp.send(null);
  } catch (e) { alert(e.message); }
  return xmlHttp.responseText;
}

var answer;
answer = newLispEval("(+ 3 4)");
document.write(answer);
document.write("<BR>ok.");
</script>
</body>
</html>
<!-- end of file -->


then I run
Code Select
newlisp.exe -c -d 1235
and open browser for location:
Code Select
http://localhost:1235//tmp/1/test1.html
and... it's work!

Thanks you.



But I still have some small problems:

1. Newlisp session not saved between requests:

after
Code Select
newLispEval("(set 'x 3)");
evaluation of
Code Select
newLispEval("(+ 'x 4)");
give me error "ERR: value expected in function + : x".

It is possible work form Javascript with one newlisp session?



2. Newlisp in server mode not support names with spaces?

Location like:
Quotehttp://localhost:1235//my">http://localhost:1235//my projects/q1/test1.html

not work for me.



3. It is possible explicit specify Windows drive letter in location?

Location like:
Quotehttp://localhost:1235//D/tmp/1/test1.html">http://localhost:1235//D/tmp/1/test1.html

not work for me.

abbat

#8
November 07, 2009, 09:19:35 AM Last Edit: December 31, 1969, 04:00:00 PM by Guest
Sorry, misprint:

instead

"newLispEval("(+ 'x 4)");"

must be

"newLispEval("(+ x 4)");"

Lutz

#9
November 07, 2009, 11:26:17 AM Last Edit: December 31, 1969, 04:00:00 PM by Guest
Quote1. Newlisp session not saved between requests:


You could save the session doing a (save "session.lsp") in the CGI program after evaluating and doing (load "session.lsp") at the beginning of each CGI process.



But a better/faster solution would be to start a second newlisp server process, which stays in memory, and use 'net-eval' to connect from it from the CGI process. newLISP processes use very little memory, so starting just another one is the preferred solution. It is also the more secured solution, because you could preload the serve with statements disabling all dangerous commands. E.g:


Code Select
(constant 'delete-file (fn () "not allowed"))

Quote2. Newlisp in server mode not support names with spaces?


Currently not supported. newLISP server mode is not meant to be a full featured web server, it doesn't do any URL back translation.


Quote3. It is possible explicit specify Windows drive letter in location?


Drive switching works like this on Windows:


Code Select
http://localhost:1235/D:/tmp/1/test1.html

If D would be the current drive, you could do:


Code Select
http://localhost:1235//tmp/1/test1.html

abbat

#10
November 07, 2009, 11:38:59 AM Last Edit: December 31, 1969, 04:00:00 PM by Guest
This is suitable for me.

Many thanks!
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