RE: Connecting to an HP 500 (was Re: RPG400-L Digest, Vol 3, Issue 242)

I changed the topic of this message to something meaningful.  When you
reply to a digest PLEASE change the topic.

> (Port is hardcoded to 4700)
> When I try to do the connect, the program errors out.  The error code is
> 3425, "A remote host has refused an attempted connect operation."

That can mean one of two things:
a) Theres no program listening on port 4700.
b) A firewall is blocking your connection, and is sending back an ICMP
message telling you about it.

It's unusual, in my experience, that a firewall is nice enough to send
back an ICMP packet.  Usually they just cut you off and let you deal with
it via a time-out.  So, I'd say most likely you're connecting to a port
that does not have a program listening to it.

What all of that boils down to, most likely, is that you're connecting to
the wrong port.

> I have no idea what that means, really.  I've googled for it, and I get a
> variety of answers, none of which make any sense in this context.  I can ping
> the printer server from a 5250 session, and from a Windows command line.

All ping tells you is that the network can send traffic to that machine,
it does not tell you whether that port is being listened to.
>From your windows box, try telnetting to port 4700.  You should get a
similar error.

> I can start the on-board printer server configuration Java app by
> hitting the IP address through a browser session.  Using the app, I can
> see that there isn't any security in effect on the printer server.

Cool!  That means I can re-configure your printer from here!  What's the
IP address?  See how convienient it is having no security?

> 1.  What causes a remote host, such as a printer server, to refuse a
> connection?

This is the normal state of things.  The only time that it does NOT refuse
the connection is when a program running on that machine calls the bind()
API for that port number, followed by the listen() API.

Since this is a print server, that software would have to be written by HP
and put in the print server's firmware.


> 2.  How do I get the print server to accept a connection?

I don't have the full details on how this device works.  If there's some
service that's available to run on port 4700, then you need to start that
service.  Otherwise, you need to connect to some service that *IS*
running.

I will tell you this...  4700 is a non-standard port number.  I don't know
of ANY protocol that usually uses 4700.  I don't know where you got 4700,
but my best guess is that it's not the port you wanted to use!

The standard port for PJL (HP "JetDirect" protocol) is 9100.  The standard
port for LPR/LPD is 515.

> 3.  Has anyone tried anything like this before?  If so, how did you diagnose
> these problems?  The manual is about four steps shy of useless.

What manual?  The printer's manual?  The sockets programming manual?  What
are you talking about?

At any rate, if you have a working method of transporting data to this
printer, run a network sniffer and see what it's sending.  Then, do the
same thing yourself.

There's a great open-source network sniffer available here:
http://www.ethereal.com