% Tikz File mqtt_pub_sub.tex
\documentclass{standalone}
\usepackage{tikz}
\usepackage{graphicx}

\begin{document}
\begin{tikzpicture}
    %\draw[help lines] (-7,-5) grid (7,5);

    % Broker
    \draw (0,0) circle (2);
    \node[] at (0,-1.5) (broker) {\textbf{Broker}};
    \node[inner sep=0pt] (broker_pc) at (0,0)
        {\includegraphics[width=0.1\textwidth]{images/pc.png}};
    
    % Publisher
    \pgfmathsetmacro\xl{-6};
    \pgfmathsetmacro\xr{-3};
    \pgfmathsetmacro\w{(\xl+\xr)};
    \pgfmathsetmacro\y{6};
    
    % Text
    \node[] at (\w/2,-\y/2-0.25) (pubs) {\textbf{MQTT Clients}};
    
    % Images
    \node[inner sep=0pt] (laptop) at (\w/2,\y/3)
        {\includegraphics[width=0.1\textwidth]{images/laptop.png}};
    
    \node[inner sep=0pt] (mcu) at (\w/2,\y/3-\y/3)
        {\includegraphics[width=0.1\textwidth]{images/muc.png}};
        
    \node[inner sep=0pt] (pc) at (\w/2,\y/3-\y/3-\y/3)
        {\includegraphics[width=0.1\textwidth]{images/pc.png}};
    
    \draw (\xl-0.25, \y/2-0.25) -- (\xl-0.25, -\y/2+0.25);  % left
    \draw (\xl, \y/2) arc (90:180:0.25);                    % top left
    \draw (\xl, \y/2) -- (\xr, \y/2);                       % top
    \draw (\xr+0.25, \y/2-0.25) arc (0:90:0.25);            % top right
    \draw (\xr+0.25, \y/2-0.25) -- (\xr+0.25, -\y/2+0.25);  % right
    \draw (\xr, -\y/2) arc (270:360:0.25);                  % bottom right
    \draw (\xl,-\y/2) -- (\xr,-\y/2);                       % bottom
    \draw (\xl-0.25, -\y/2+0.25) arc (180:270:0.25);        % bottom left
    
    % Subscriber
    \pgfmathsetmacro\xl{3}
    \pgfmathsetmacro\xr{6}
    \pgfmathsetmacro\w{(\xl+\xr)};
    \pgfmathsetmacro\y{6}
    
    \node[] at (\w/2,-\y/2-0.25) (subs) {\textbf{MQTT Clients}};
    
    % Images
    \node[inner sep=0pt] (server) at (\w/2,\y/3-1)
        {\includegraphics[width=0.1\textwidth]{images/server.png}};
    
    \node[inner sep=0pt] (sub_mcu) at (\w/2,\y/3-3)
        {\includegraphics[width=0.1\textwidth]{images/muc.png}};
    
    \draw (\xl-0.25, \y/2-0.25) -- (\xl-0.25, -\y/2+0.25);  % left
    \draw (\xl, \y/2) arc (90:180:0.25);                    % top left
    \draw (\xl, \y/2) -- (\xr, \y/2);                       % top
    \draw (\xr+0.25, \y/2-0.25) arc (0:90:0.25);            % top right
    \draw (\xr+0.25, \y/2-0.25) -- (\xr+0.25, -\y/2+0.25);  % right
    \draw (\xr, -\y/2) arc (270:360:0.25);                  % bottom right
    \draw (\xl,-\y/2) -- (\xr,-\y/2);                       % bottom
    \draw (\xl-0.25, -\y/2+0.25) arc (180:270:0.25);        % bottom left
    
    % arrows
    \draw[ultra thick, ->] (mcu) -- (broker_pc);
    \draw[ultra thick, ->] (laptop) -- (broker_pc);
    \draw[ultra thick, ->] (pc) -- (broker_pc);
    \draw[ultra thick, ->] (sub_mcu) -- (broker_pc);
    
    \draw[dashed, ultra thick, <-] (server) -- (broker_pc);
    \draw[dashed, ultra thick, ->] (broker_pc.10) to (sub_mcu.north west);
    
    % legend
    \draw[dashed, ultra thick, ->] (-4,-4) -- (-1,-4);
    \node[] (Sub) at (-2.5,-4.25) {Subscribe};
    
    \draw[ultra thick, ->] (1,-4) -- (4,-4);
    \node[] (Pub) at (2.5,-4.25) {Publish};
    
\end{tikzpicture}
\end{document}