introduction.tex

\chapter{Introduction}


\section{Abstract}
EtherLab\footnote{ \url{http://etherlab.org/en/components.php}} is a
set of open-source software developed by IgH to build real-time
control applications. This tutorial explains how to install two
EtherLab components: TestManager (real-time visualization software) and
DLS (Data Logging Service). It also provides an easy overview
before you read the official documentation.

\section{Architecture overview}
An overview of the architecture can be seen in Figure \ref{fig:architecture}.

\begin{figure}[h!]
  \includegraphics[width=\textwidth]{genpicts/dls-arch.eps}
  \caption{Architecture overview}
  \label{fig:architecture}
\end{figure}


\begin{itemize}

\item There are three computers: the controller, the viewer, and the recorder.

\item On the controller, the control application exports its
  channels in shared memory (SHM), then another process running
  the PdServer library publishes the channels on the network through the MSR
  protocol (TCP port 2345 by default).
  Once the channels are exported on the network, any client that
  speaks the MSR protocol can display or record the channels.

\item On the recorder, the program \texttt{dlsd} (Data Logging Service
  Daemon) records the selected channels on the file system (FS).  The
  program \texttt{dls\_ctl} manages the configuration files for
  \texttt{dlsd} via the file system, for example by configuring
  the list of channels to record.
  \texttt{dls\_view} is a simple viewer that can read the data files
  written by \texttt{dlsd} directly.

\item On the viewer, the program \texttt{testmanager} connects
  directly to PdServer to display the channels in real time.  Meanwhile,
  \texttt{dlsgui} is an advanced data viewer for DLS that connects to
  \texttt{dlsd} via a specific network protocol (TCP port 5384 by default)
  to plot recorded data.

\end{itemize}