/*
 *
 *  VRPN Header Format
 *
 * +------------+------------+------------+------------+
 * |                    Total Length                   |
 * +------------+------------+------------+------------+
 * |                Timestamp (Seconds)                |
 * +------------+------------+------------+------------+
 * |              Timestamp (Microseconds)             |
 * +------------+------------+------------+------------+
 * |                       Sender                      |
 * +------------+------------+------------+------------+
 * |                        Type                       |
 * +------------+------------+------------+------------+
 * |                       padding                     |
 * +------------+------------+------------+------------+
 *
 * Total Length = Padded Payload Length + Padded Header Length.
 * Padded Header Length = 24 bytes.
 * Padded Payload Length = Payload Length + (Payload Length % 8).
 *
 * All header fields are 32-bit integers sent in network order.
 * Both header and payload are padded to end on 8-byte boundaries.
 *
 * Implementation in vrpn_Connection::marshall_message().
 *
 */

/*
 *
 *  VRPN Connection setup sequence
 *
 * Server opens a TCP socket and listens() on port - default vrpn_DEFAULT_LISTEN_PORT_NO
 * Client connects() to port
 * Server and client both write a COOKIE
 * Server and client both wait (nonblocking) for a COOKIE and
 *   verify version #, etc.
 * If either peer is requesting remote logging, a log_description message
 *   is sent.
 * Server and client both open UDP sockets.
 * Server and client both send udp_description messages.
 * Server and client both send sender_description messages for all senders
 *   registered locally.
 * Server and client both send type_description messages for all types
 *   registered locally.
 *
 * Implementation in vrpn_Connection::setup_new_connection(),
 *   finish_new_connection_setup(),
 */

/*
 * VRPN Cookie Format
 *
 * +------------+------------+------------+------------+
 * +    'v'     |    'r'     |    'p'     |    'n'     +
 * +------------+------------+------------+------------+
 * +    ':'     |    ' '     |    'v'     |    'e'     +
 * +------------+------------+------------+------------+
 * +    'r'     |    '.'     |    ' '     |     X      +
 * +------------+------------+------------+------------+
 * +     X      |    '.'     |     Y      |     Y      +
 * +------------+------------+------------+------------+
 * +    ' '     |    ' '     |     L      |   padding  |
 * +------------+------------+------------+------------+
 * +                      padding                      |
 * +------------+------------+------------+------------+
 *
 * XX = major version number (2 ASCII characters)
 * YY = minor version number (2 ASCII characters)
 *  L = remote log mode requested (ASCII '0', '1', '2', or '3')
 *
 * This cookie is in ASCII so that humans scanning a dump can
 * quickly determine whether or not it is a VRPN session.
 */

/*
 * VRPN Log description message:
 *
 * type = vrpn_CONNECTION_LOG_DESCRIPTION (-4)
 * sender = logging mode (0, 1, 2, or 3)
 * payload length = strlen(logfile name) + 1
 * data = null-terminated ASCII string giving pathname of file to log to
 */

/*
 * VRPN UDP description message:
 *
 * type = vrpn_CONNECTION_UDP_DESCRIPTION (-3)
 * sender = UDP port number to contact
 * payload length = strlen(IP address) + 1
 * data = ASCII string containing host's IP address
 */

/*
 * VRPN Sender description message:
 *
 * type = vrpn_CONNECTION_SENDER_DESCRIPTION (-1)
 * sender = ID of sender
 * payload length = 5 + strlen(sender name)
 * data = 
 *
 * +------------+------------+------------+------------+
 * +             length of sender name + 1             |
 * +------------+------------+------------+------------+
 * +                    sender name                    |
 * +------------+------------+------------+------------+
 * +                        ...                        |
 * +------------+------------+------------+------------+
 *
 * N.B. There is redundant length data here
 */

/*
 * VRPN Type description message:
 *
 * type = vrpn_CONNECTION_TYPE_DESCRIPTION (-2)
 * sender = ID of type
 * payload length = 5 + strlen(sender name)
 * data =
 *
 * +------------+------------+------------+------------+
 * +              length of type name + 1              |
 * +------------+------------+------------+------------+
 * +                     type name                     |
 * +------------+------------+------------+------------+
 * +                        ...                        |
 * +------------+------------+------------+------------+
 *
 * N.B. There is redundant length data here
 */

/*
 * VRPN disconnect message:
 *
 * type = vrpn_CONNECTION_DISCONNECT_MESSAGE (-5)
 * sender = 0
 * payload length = 0
 *
 * This message is never sent over the wire;  it is written into logs
 * to mark the point at which a connection was broken.
 */