[NTLUG:Discuss] Getting out past a firewall easiest

[Kipton Moravec]

I am developing a system that will be a sophisticaded appliance for certain 
businesses.

Part of the system monitors other equipment and if an error occurs sends 
some sort of message to a server on the Internet.  In addition I want it to 
periodically check in to get software updates automatically.

The controller will be a simple Linux PC.  Depending on the installation 
the Internet access will be dial-up or hook into the business's existing 
network with Internet access.

I am looking for the easiest approach for the system to get out and access 
the server on the Internet.

I am looking at probably a socket to socket connection.  With custom 
software (C program or script) on the client and server side to do the 
business needed.

Since many of you are Network Admins, what is the best way for me to do 
this, without upsetting the network security and firewall?  I believe if 
there is a firewall then the client must initiate the contact with the 
server.  Since that is the case with dial-up also that will be our 
model.  And the client will check-in once a day, (later once per week) for 
status reporting and to see if there are any updates. The server will not 
be able to initiate a dialog with the client.

Are there any other gotcha's that I need to watch out for?   I am assuming 
the client can initiate a FTP session to download the newest software. Is 
that a good assumption or could it possibly be blocked?

The installers will be unsophisticated.  And there is no telling what the 
business will have.   Which is one reason we have to administer from a 
central location.  There are the potential of  tens of thousands of systems.

Kip