Question about how to start building a web application

I have extensive experience with Java, c++, and python, and a little experience with JavaScript. I have built a lot of desktop applications for personal use with Java, and I have a good understanding of JavaScript, CSS, and html. However, I am new to making web applications, and I cannot seem to find any good tutorials or information on how to start making a web application. I am comfortable using the Spring Framework, and right now I am struggling to get my Spring application running on AWS. First, I need to start by running multiple Spring applications to run on different ports. I can only seem to run one at a time, and I also cannot figure out how to run a spring application from the aws console. First, does anyone have advice for how to get a Spring project to run on different ports on one machine? Second, what is the best way to host spring applications, and what is the best free hosting platform out there now? <br>Thanks for the help.