SMTP: nope, the server accepts your connection before you do anything<p>VoIP: generally negotiated somehow before the UDP &quot;pushing&quot; happens<p>scp: just because in your mind it&#x27;s a &quot;push&quot; doesn&#x27;t make it so.  In reality the other machine is sending you acks, without which your machine wouldn&#x27;t continue &quot;push&quot;ing and thus, again consent is required.  finally you&#x27;re <i>logged in</i> to that other machine which nearly universally equates to consent