How to generate more arrows

Question

I have this:

This is my latex code

\documentclass[tikz,border=10pt,12pt]{standalone}
 \usetikzlibrary{arrows}
 \usepackage{pstricks}
 \usetikzlibrary{calc}
 \newcommand*\circled[1]{\tikz[baseline=(char.base)]{
    \node[shape=circle,fill=blue!20,draw,inner sep=2pt] (char) {#1};}}

\begin{document}

\begin{tikzpicture}[>=stealth']

% Locations
\def\ClientToServer{++(9,0)}
\def\ServerToClient{++(-9,0)}
\def\Lifeline{++(0,-15)}%Longitud hacia abajo

% Lifelines
\path (0,0)           node[draw] (Client) {\blue{\textbf{Client}}}
\ClientToServer node[draw] (Server) {\blue{\textbf{Server}}};
\draw (Client) -- \Lifeline (Server) -- \Lifeline;

% Blocks
\path (Server)
++(0,-1) node (BeginProcess) {} node[below right] {}
++(0,-1) node (EndProcess)   {};


% Calls
\draw[->] (BeginProcess)\ServerToClient -- node[above] {\circled{1} one} 
(BeginProcess);

\draw[->] (EndProcess) -- node[above] {\circled{2} two } \ServerToClient;

\node[left=0mm,yshift=-3cm] {\circled{3} yesss};

\node[left=0mm,yshift=-5cm] {\parbox{1.7in}{\circled{4} hello hello hello hello hello}};

draw[->] (9,-6) -- node[above] {uiiiiuuuuuuuuuuuuuuuuu} (-9,-6);%<---- ?

\node (B1) [fill,color=black,text width=1.2cm] at (9,-15) {};
\node (B2) [fill,color=black,text width=1.2cm] at (0,-15) {}; 

\end{tikzpicture}

\end{document}

I want to generate more arrows between client-server and server-client. But no more is generated. I use basic commands like:draw[->] (9,-6) -- node[above] {uiiiiuuuuuuuuuuuuuuuuu} (-9,-6); but not generate.

I want can create more arrow like:

Thank you!