Using packaged Servoy installer (servoy_installer.jar) will let you run Smart Client, Web Client, Headless Client.
Using your own Java server (Tomcat, JBoss, GlassFish, etc) and deploying a Servoy WAR file will let you run Smart Client, Web Client, Headless Client, AND NGClient.
You shouldn't run separate servers just to handle different deployment types (Smart vs Web vs NG) unless you have some special circumstance and you understand what you're doing, as you will have data broadcasting issues potentially.
Why did Servoy do this, instead of just upgrading their installer? Not 100% sure, but likely to move to more standards based. New users have a tough time understanding they have to deploy some custom server. Then they want someone else to host it, and there is very limited specialized Servoy hosting options. However, if you switch to WAR deployment, you can use many different hosting providers that provide specialized Java Application Server hosting. For example, I did a presentation at Servoy World a few years ago where I deployed an application to Microsoft Azure in under 10 minutes. Preso attached here:
NextGenerationCloud.pdf
. Page 15 starts with the details. Gives a good list of the benefits of WAR deployment via PaaS providers.
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