title: Should my server use both TCP and UDP?
body: <p>I'm writing a client/server application and really can't find guides that fit my need. Doing it on my own leads me to many design flaws before I've even begun. For instance the server should update every client as to its state many times each second. I assumed I couldn't update every client individually, but UDP broadcasts should fix that. But I still need a TCP channel to reliably communicate with each client for things like: Chat messages, user input etc.</p>
  
  <p>Researching this topic it seems that it's possible for a server to use both protocols simultaneously - but only possible (not sensical). Nobody suggests such an approach, in fact I gather from <a href="http://www.isoc.org/INET97/proceedings/F3/F3_1.HTM#s2">this article</a> that it's rather bad to use both.</p>
  
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  <p>Now I'm very confused as to how I should handle data in my server. Unless I've completely misunderstood something about packet loss, I want to guarantee that user input resulting in 'server-request-packets' are not lost. Every answer on SO about guaranteeing delivery with UDP say, without fail, use TCP. What's more frustrating is that every server/client program I can imagine at the very least needs some of its messages guaranteed delivered (for instance 'disconnect' messages?).</p>
  
  <p>Should I use UDP, TCP, both or am I just thinking completely wrong about this?</p>