ml#t:OnError">OnError</a></code>: Error handler
</li><li> IO r: The function starts a new thread on which the 
           the server is working; 
           the thread from which the function was called
           continues in this action.
           Its return value is also the result of <em>withServerThread</em>.
           When the action terminates,
           the new thread is terminated internally.
</li></ul></div></div><div class="top"><p class="src"><span class="keyword">type</span> <a name="t:Regis