Uninformed - vol 8 article 3

Non-control messages are considered data messages and contain some form of actual data for the user, whether it be text chat data, incoming file data, a command for the local shell service, or a response from the remote shell service. These various types of data are differentiated by the value of the message header's Type field.

The Chat Data Message is used to transmit text chat data between SteganRTP applications. This type of data requires no context information, thus the message payload contains only a single field, Chat Data, as described by Figure

below.

**Figure:** SteganRTP Chat Data Message.
$\begin{figure}\begin{center} \begin{verbatim}0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 ... ...-+-+-+-+ \vert Chat Data \vert ! ! . .\end{verbatim} \end{center}\end{figure}$

The File Data Message is used to transmit data file contents between SteganRTP applications. Because multiple file transfers may be in progress at any given time, this type of data must be accompanied with context information indicating which file transfer the chunk of data belongs to. Figure

below describes the format of a File Data message.

**Figure:** SteganRTP File Data Message.
$\begin{figure}\begin{center} \begin{verbatim}0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 ... ... \vert +-+-+-+-+-+-+-+-+ \vert ! ! . .\end{verbatim} \end{center}\end{figure}$

The File ID field's value is a unique file ID number chosen for the particular file transfer taking place and is used to indicate which file transfer the chunk of data contained in the File Data field belongs to. The File Data field is a chunk of data from the file being transferred. The proper order for reconstruction of the file chunks transferred by these messages is ensured by the message header's sequence number.

The Shell Input Data and Shell Output Data Messages are used to transmit shell input to, and receive shell output from, a remote SteganRTP shell service, respectively. This type of data requires no context information, thus the message payload contains only a single field, Shell Data, as described by Figure

below.

**Figure:** SteganRTP Shell Data Message.
$\begin{figure}\begin{center} \begin{verbatim}0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 ... ...+-+-+-+ \vert Shell Data \vert ! ! . .\end{verbatim} \end{center}\end{figure}$