RE: [Jython-users] Using Jython as an interactive Java debugger.

[Adrian S. J. <as...@pa...>]

> From: Paul Giotta
>
> I am currently have a side project that will do something like this. It
> is a module that implements a telnet daemon that runs as a java thread.
> When someone connects, it starts a jython interpreter and uses this as
> the shell for user interaction. Thus, if this is embedded in a running
> server, you can connect using an ordinary telnet client and manipulate
> object running in the same VM. This is still work in progress, but some
> of the sticky points so far:
>
>    - Implementing telnet: I tried to find a java telnet daemon that I
> could adapt or borrow code from. There does not seem to be any yet. Also
> getting complete and understandable documentation for the telnet protocol
> is not that easy (every time I use a new telnet client, it starts trying
> to negotiate some other connection parameter that i cannot find in any
> documentation).

I've implemented telnet-like daemons in C++ and Smalltalk. The
one thing I have learnt is that if you don't offer any telnet option
codes, the clients tend not to try to negotiate anything.
The other thing you can do is just send a WONT in response to any option
you don't understand that the client sends as a DO, and a DONT when you're
sent a WILL.

>    - If I try to run multiple instances of jython interpreters in
> different threads, bad things start to happen. It is not really critical
> that I handle multiple connections simultaneously, but I would not expect
> this to be a problem. :-(

What sort of problems? I've just got a mud-like engine running with multiple
interpreters each in their own thread, and had very few problems. The
hardest
thing I had to do was to redirect stdout/stderr back to the telnet
connection,
as it seems that Jython 2.0 grabs stdout/stderr at the point that you
initialise
it, rather than just using Java's stdout.

> -Paul

Adrian.