How to maintain a persistant network-connection between two applications over a network?

Question

I was recently approached by my management with an interesting problem - where I am pretty sure I am telling my bosses the correct information but I really want to make sure I am telling them the correct stuff.

I am being asked to develop some software that has this function:

• An application at one location is constantly processing real-time data every second and only generates data if the underlying data has changed in any way.
• On the event that the data has changed send the results to another box over a network
• Maintains a persistent connection between the both machines, altering the remote box if for some reason the network connection went down

From what I understand, I imagine that I need to do some reading on doing some sort of TCP/IP socket-level stuff. That way if the connection is dropped the remote location will be aware that the data it has received may be stale.

However management seems to be very convinced that this can be accomplished using SOAP. I was under the impression that SOAP is more or less a way for a client to initiate a procedure from a server and get some results via the HTTP protocol. Am I wrong in assuming this? I haven't been able to find much information on how SOAP might be able to solve a problem like this.

I feel like a lot of people around my office are using SOAP as a buzzword and that has generated a bit of confusion over what SOAP actually is - and is capable of.

Any thoughts on how to accomplish this task would be appreciated!

Answer 1

SOAP certainly won't tell you when the data source goes down, though you could use "heartbeats" to add that.

Probably you are right and they are just repeating a buzz word, and don't actually know much about what SOAP is or does or have any real argument for why it ought to be used here.

Answer 2

I think SOAP is the wrong tool. SOAP is a spec for exchanging structured data. For your problem, the simplest thing would be to write a program to just transfer data and figure out if the other end is alive. Sockets are a good way to go. There are lots of socket programming tutorials on the net. Pick your language, and ask Mr. Google. Write a couple of demo programs to teach yourself how it works. Ask if you have more specific questions.

For the problem, you'll need a sender and a receiver. The sender sends data when it gets it, the receiver waits for data and hands it off when it arrives. Get that working first. Next, add in heartbeats; a message that says "I'm alive", sent periodically. Get that working next. You'll need to be determine the exact behavior you want -- should both sides send heartbeats to the other end, the maximum time you are willing to wait for a heartbeat, and what action you take should heartbeats stop arriving. The network connection can drop, the other end can crash, the other end can hang, and perhaps there are other conditions you should think about (e.g., what if the real time data is nonsense?). Figure out how to handle each condition, and code up the error handling. Test it out, and serve with a side of documentation.