# I get this error: pdflatex.exe: A connection attempt failed because

Good day all. I am getting this error:

pdflatex.exe: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. pdflatex.exe: Data: connect failed in tcp_connect()

which makes my code take very long to compile, although it seems to compile correctly. I am compiling with pdflatex. Has anyone experienced the same problem?

My script:

\documentclass[paper=a4]{article} % A4 paper and 11pt font size
\usepackage[english]{babel} % English language/hyphenation
\usepackage{amsmath,amsfonts,amsthm} % Math packages
\usepackage{graphicx}

\begin{document}
\begin{titlepage}
\thispagestyle{empty}
\end{titlepage}
\setcounter{page}{1}
\newpage
\section*{Introduction}
The purpose of this project is to
\subsection*{Problem}
The system to be analysed through the duration of this project is a two-car train, interconnected with a spring, as shown in Figure 1:\\
\newline
\begin{figure}[h!]
\centering
\includegraphics[scale=0.5]{System1.png}
\caption{two-car train, interconnected with a spring}
\end{figure}
\newline
It was initially proposed to use the absolute displacements of the carts as state variables, but it turns out that this results in the system becoming unobservable. The choice was thus made to choose the state variables:\\
\begin{align}
x =
\begin{bmatrix}
\Delta \\
v_1 \\
v_2
\end{bmatrix}
\end{align}
where $v_1=\dot{z_1}$ and $v_2=\dot{z_2}$ are the speeds of cars 1 and 2, respectively.\\
Note that we are dealing with a third order system, as we have 3 state variables.
\newline
The state equation of the system is given by:\\
\begin{figure}[h!]
\centering
\includegraphics[width=0.5\textwidth]{state_eqn.png}
\end{figure}
\newpage
and the observation equation by:\\
\begin{figure}[h!]
\centering
\includegraphics[scale=0.1]{obs_eqn.png}
\end{figure}
\newline
We thus have a single input single output (SISO) system with the voltage going to the motor of the first car as the input and the speed of the first car as the output.\\

We now substitute the following constants into the dynamics matrix A, the input matrix B and the observation matrix C:\\
\begin{center}
$M_1=M_2=1kg$\\
$K=40N/m$\\
$k=2Vs$\\
$R=100\Omega$\\
$r=2cm$\\
\end{center}
We then get the following matrices:\\
\begin{align}
A =
\begin{bmatrix}
0 & -1 & 1 \\
40 & -0.01 & 0 \\
-40 & 0 & 0
\end{bmatrix}\\
\end{align}

\begin{align}
B =
\begin{bmatrix}
0\\
0.01\\
0\\
\end{bmatrix}
\end{align}
\begin{align}
C =
\begin{bmatrix}
0 & 1 & 0\\
\end{bmatrix}
\end{align}

\subsection*{Controllability and observability}
Before we start the analysis, it will be useful to confirm that the system at hand is indeed controllable and observable.\\
\newline
To be controllable, the rank of the controllability test matrix, defined by\\
\begin{align}
Q =
\begin{bmatrix}
B & AB & A^{2}B
\end{bmatrix}
\end{align}
has to be of the same order as the system. To be observable, the rank of the observability test matrix, defined by\\
\begin{align}
N =
\begin{bmatrix}
C' & A'C' & A'^{2}C'
\end{bmatrix}
\end{align}
has to be of the same rank as that of the system. Computing matrices Q and N and using the rank() function in MATLAB shows that the ranks of both matrices are 3, and thus equal to the order of the system. We now know that the system is controllable and observable and can thus use the tools at our disposal to design a controller for this system.
\section*{Question A}
Assuming all states are measured for feedback purposes, we will now determine the gain matrix

\end{document}

• Welcome to TeX.SX! A tip: If you indent lines by 4 spaces, then they're marked as a code sample. You can also highlight the code and click the "code" button ({}) or hit Ctrl+K. – Claudio Fiandrino Apr 25 '14 at 8:38
• Good day! Thank you very much, will do that in the future! – Jonny Apr 25 '14 at 8:42
• Welcome to TeX.SX! Your code does not compile for all users since there are some graphic files included. After commenting the lines the code runs without the error message you provided. I suppose, it is some strange issue with your TeX installation and/or your operating system. – user31729 Apr 25 '14 at 8:48
• Are you using MiKTeX offline? MiKTeX tries to fetch missing packages on-the-fly, but this requires you to be online when that happens. – Nicola Talbot Apr 25 '14 at 8:50
• Thank you Christian for your effort and thank you Nicola for solving my problem (-: – Jonny Apr 25 '14 at 8:58