Re: How do I know a connect was rejected, and why?

[Patrick Caulfield <patrick@pandh.demon.co.uk>]

On Tue, Feb 01, 2000 at 02:24:55PM +0000, Steve Whitehouse wrote:
> > 
> > Dumb question but the answer isn't obvious from looking at manpages or 
> > code...
> > 
> > If I do a connect, and the connect is rejected, how can I tell?  It
> > seems the connect call succeeds, but when you then try to read data
> > from the socket it fails.
> > 
> If connect() returns -1, then you've got an error of some sort
> getsockopt(...DSO_DISDATA..) to get at the disconnect data. It returns
> a status as well as the actual (optional) data.
> 
> > There's a specific "rejected" link state, but I don't see how that's
> > visible from the application.  And besides, I need to have the reject
> > code. 
> > 
> You can use getsockopt(...DSO_LINKINFO...) to find out the logical link
> state of the socket, but the only other method at the moment is to
> parse /proc/net/decnet (see my previus post on the list) which is not
> whta I'd recommend...
> 
> > One scenario: the clean way to do sethost to non-cterm hosts is to try
> > to connect to cterm, then if that fails with reason == no such object,
> > retry with the other object number.
> > 
> > 	paul
> 
> You should be able to grab the reason with the DSO_DISDATA call. The only
> thing to remember is to close() the failed socket and open a new one to
> try and connect to a different object. The disconnect data responses
> have not been tested very well though, you may well uncover some bugs there,

dnprogs does this - see libdap/connection.cc(connerror) and 
libdaemon/dnet_daemon.cc(dnet_reject).

It seems to work OK as far as I've had chance to test it. ie you get 
authorisation errors when you send a bad password and similar.

Patrick


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