// Called when the DNS query completes (either synchronously or asynchronously). Checks for failure and
// starts the first connection attempt if it succeeded. Returns true if the operation will be asynchronous,
// false if it has failed synchronously.
private bool DoDnsCallback(IAsyncResult result, bool sync)
{
Exception exception = null;
lock (_lockObject)
{
// If the connection attempt was canceled during the dns query, the user's callback has already been
// called asynchronously and we simply need to return.
if (_state == State.Canceled)
{
return(true);
}
if (_state != State.DnsQuery)
{
NetEventSource.Fail(this, "MultipleConnectAsync.DoDnsCallback(): Unexpected object state");
}
try
{
_addressList = Dns.EndGetHostAddresses(result);
if (_addressList == null)
{
NetEventSource.Fail(this, "MultipleConnectAsync.DoDnsCallback(): EndGetHostAddresses returned null!");
}
}
catch (Exception e)
{
_state = State.Completed;
exception = e;
}
// If the dns query succeeded, try to connect to the first address
if (exception == null)
{
_state = State.ConnectAttempt;
_internalArgs = new SocketAsyncEventArgs();
_internalArgs.Completed += InternalConnectCallback;
_internalArgs.CopyBufferFrom(_userArgs);
exception = AttemptConnection();
if (exception != null)
{
// There was a synchronous error while connecting
_state = State.Completed;
}
}
}
// Call this outside of the lock because it might call the user's callback.
if (exception != null)
{
return(Fail(sync, exception));
}
else
{
return(true);
}
}
