\begin{tikzpicture}
\begin{umlseqdiag}

\umlactor{Device}
\umlactor{Broker}
\umlactor{Central}

\begin{umlcall}[op={sub(dev/\#/online)}]{Central}{Broker}
\end{umlcall}

\begin{umlcall}[dt=15, op={con(dev/123/online, 0)}]{Device}{Broker} \end{umlcall}
\begin{umlcall}[dt=5, name=pub,op={pub(dev/123/online, 1)}]{Device}{Broker} \end{umlcall}

%\begin{umlcallself}[dt=5, op={terminate()}]{Device}\end{umlcallself}

%\umlnote{death}{woop}
\umlnote[x=-3,y=-2]{sb-pub}{After this the device drops off the Wi-Fi}


\begin{umlcall}[dt=10, op={pub(dev/123/online, 0)}]{Broker}{Central} \end{umlcall}

%\umlsdnode[dt=20]{Central}
%\umlsdnode[dt=5]{Broker}
%\begin{umlcall}
%\end{umlcall}

\iffalse
\begin{umlcall}{A}{C}
	\begin{umlcall}{C}{A}
	\end{umlcall}

	\begin{umlcall}[dt=10]{B}{C}
		\begin{umlcall}{C}{B}
		\end{umlcall}

		\begin{umlcall}[return=1]{B}{C}
		\end{umlcall}
	\end{umlcall}

	\begin{umlcall}[dt=20, return=1]{A}{C}
	\end{umlcall}

\end{umlcall}
\fi
\end{umlseqdiag}
\end{tikzpicture}