Kill Packets

TABLE OF CONTENTS:

1. Introduction and Background
2. The Sequence of Activities
3. Formats
4. Further Help
5. Kill Packet Contents

INTRODUCTION AND BACKGROUND:
This is the packet used by the GCN system to signal the remote site's computer that the Internet socket connection is going to be broken shortly. This allows the remote site to terminate their connect in an clean manner. There are times when the GCN system needs to stop activities and so as a more graceful way of breaking the socket connection it signals the remote site by writing this Kill packet to the socket. Unlike all the other packet types which should be immediately written back to the GCN system to verify receipt, these Kill packets need not be written back, because the GCN system is very likely to be done by then.

These Kill packets are used only with socket connections. They are never sent to sites using the other distribution methods (e-mail, (s)pager, phone, etc).

THE SEQUENCE OF ACTIVITIES:
1) GCN needs to shut down all communication links. There are two reasons that motivate these shutdowns: (a) The GCN program needs to be terminated and restarted to load a new version of the software. (b) A new version of the "sites.cfg" file needs to be loaded.
2) It writes a Kill Packet to all active Internet socket connections.
3) It closes the socket connection at the GCN end.
4) The remote sites should not echo back this packet (as they do for all the other packet types).
5) The remote sites program should drop into a mode of monitoring for a reconnection attempt.

FORMATS:
The format of the KIll packet is described in the socket definition document to get the details (this is packet_type=4). A breif description of the packet format and contents is also listed below.

FURTHER HELP:
For more information, please contact me:
Phone: 301-286-3106
E-mail: scott@lheamail.gsfc.nasa.gov

The KILL packet consists of 40 four-byte quantities.  It is used to send a
signal the site-end of the socket connection that GCN is going to close
the connection immediately (within milliseconds).  This is the only socket
packet that is never echo-ed back to the GCN system.  The order and contents
are listed in the table below.  They have the same function, meaning, and
content as the items of the same name in the packet types 1-3.

Declaration  Index   Item         Units           Comments
Type                 Name
-----------  -----   ---------    ----------      ----------------
long         0       pkt_type     integer         Packet type number (=4)
long         1       pkt_sernum   integer         1 thru infinity
long         2       pkt_hop_cnt  integer         Incremented by each node
long         3       pkt_sod      [centi-sec]     (int)(sssss.sss *100)
long         4-38    spare[35]    integer         140 bytes for the future
long         39      pkt_term     integer         Pkt Termination (always = \n)