Hi
Simple Server won’t play video – it’s really just a test/demo app.
There are loads of applications which support Syphon and play video – the grid on the Syphon website has quite a few – though many of them will be overkill for your needs, I can’t think off the top of my head of something which only does video playback.
What are you ingesting the Syphon server with? It’s somewhat unusual to have an application with Syphon input which doesn’t also play video itself.