offline message in network chat application C#
<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="http://stackoverflow.com/questions/3156344/offline-message-in-chat-application-c">offline message in chat application C#</a>  </p>
</blockquote>



<p>Hai. I'm developing an office messenger app just like Network assistant (http://www.gracebyte.com/nassi/). One of the features is broadcasting message to all contacts in network. but i have problem in sending message to offline contact. i mean if there's one (or more) of my contacts is offline, but i still wanna send message, how can i guarantee he'll get my message?</p>

<p>i'm using peer-to-peer, not client-server. as far as i know an app like Network Assistant doesnt have any servers. so, is there any other ways except using server to keep the message for offline contacts? i dont find the way to differentiate offline and online contacts too :(</p>

<p>any of you knows the solution? I develop it using C#.</p>

<p>thank you</p>
