Where to begin...? - Programming with Java on a Hosted Server

Hiya. I've been working with Java for two-and-a-half years now through my university(s), and consider myself relatively experienced in the language. However, I've recently decided to put my knowledge to good use by applying them to real-world situations. My current project, just started, is to collect information, generate a graph image from that information, and then return the path of that image, all upon invocation from an outside server. The program itself shouldn't be too difficult as I have little trouble with the programming side, but I have no idea where to begin when attempting to make a server-based file that can be invoked and called from an outside client.

Networking and server-side things have always been my weakness, so I've avoided them until now. My friend informed me that I can do this via a Java Web Service, but after looking at Oracle's page on the topic, it all went over my head, especially with regard to the fact that I've never worked with servers before. I am somewhat experienced with sockets, and have written a basic (crappy) webserver program in Java that ran through the eclipse client, but that's the extent of my knowege.

I suppose I should mention I have moderate experience with socket programming and didn't have any particular difficulties with it, so would that be the route to go? Are there any tutorials for someone in my position with no server experience but fair programming experience? Or could someone at least set me in the right direction? Thank you!

You could look at doing this from a servlet point of view: install a java application server such as JBoss or Tomcat, and deploy the application jar/war there. If all you wish to do is create something as simple as an image, you could send the information via an http POST request, then have the servlet process the data and output the graph as an image dynamically to the client. If you choose to go this route, you need to install the server (jboss, tomcat, or what have you) and write the application...I typically run a test server on my local computer, and deploy and test there from a J2EE environment in Eclipse. Tons of tutorials out there to walk you through the process.