[vsnet-grb 277148] A Redundant VOEvent Ver 2.0 server now available in GCN

Wed Nov 25 01:12:26 JST 2015

TO:  All GCN Notice recipients
RE:  A Redundant VOEvent Ver 2.0 server now available
DT:  24 Nov 2015

If you are not interested in or using GCN VOEvents, you can stop reading.

INTRODUCTION:
Another version 2.0 VOEvent server has been added
to the constellation of VOEvent servers in GCN.
For a while there has been only a single version 2.0 server
(and two version 1.1 servers), but now there are 2 version 2.0 servers
providing redunancy on the 2.0 stream.
The table of all VOEvent servers is:

      Version 2.0 Servers:
      68.169.57.253   8099
      45.58.43.186    8099   <== The new server!

      Version 1.1 Servers:
      209.208.78.170  8099
      50.116.49.68    8099

All 4 servers have the full compliment of the publically available
GCN Notices in VOEvent format.  You can connect to them anonymously
and get all the Notices produced by all the contributing missions and projects,
or you can use a configuration file to allow filtering of the Notices.
All 4 servers listen for a connection on port_number 8099.

VERSION HISTORY and FUTURE:
Even though the most recent version of VOEvents is 2.0,
version 1.1 is still supported by GCN because a couple sites
are locked into a software package that requires Ver 1.1.
For the rest of the customers, you are encouraged to use 2.0
(by connecting to those two servers).

EXCERPTS FROM PREVIOUS GCN VOEVENT ANNOUNCEMENTS:

DEMONSTRATION CLIENT PROGRAM:
To facilitate quick and easy connection to this new service,
a demo client program (voevent_client_demo) is available.
It can be downloaded from
     http://gcn.gsfc.nasa.gov/gcn/voevent_client_demo.c
This GCN/TAN client is a clean, simple, standalone client written in C.
It needs no additional libraries or other software packages installed
on your system.  It has the basic parts to (a) establish and maintain
a connection to a server, (b) receive and acknowledge VOEvents, and
(c) tell you when there are problems.
Usage:
     voevent_client_demo  <ip_num>   <port_num>
Example:
     voevent_client_demo  45.58.43.186  8099

CONNECTION PROTOCOL:
A connection between the client and a server is done using the so-called
"vTCP" protocol.  It is the standand TCP protocol with a "v"OEvent adjustment
involving (a) Imalive packet exchange, (b) a 2-part writing/reading action, and
(c) the explicit ack/nacking-ing of the VOEvents received.  The imalives
allow for both ends to monitor the vitality of the end-to-end connection,
and take corrective action if nothing has been recevied within 2or3
of the 60-sec intervals the imalives are sent.  The 2-part writing/reading
starts with a 4-byte quantity sent first that indicates the length of the VOEvent
message that will be sent next (so the client reads 4 bytes, then knows
how much to read to get the message).  The acking/nacking allows the server
to keep track that the client has correctly received the full VOEvent message.
The TCP/IP VOEvent protocol is described in
     http://www.ivoa.net/Documents/Notes/VOEventTransport/ .
If you already have a client which implements this vTCP protocol,
you can use it to connect to the GCN/TAN VOEvent servers.
(The voevent_client_demo is just a bare-bones example to get people started
if they have no prior experience with VOEvents.  You can also use
voevent_client_demo to connect to other VOEvent servers using the vTCP protocol.)

FILTERING:
Even though votan is a server and you can connect anonymously[1],
if you register with GCN/TAN, you can receive all the regular
filtering capabilities of the original GCN system.
Votan is able to accomplish this by checking your IP Number (IPN)
when you connect.  If your IPN matches an entry in the votan sites.cfg file,
then it uses that configuration to determine which Notice types
you want to receive plus all 16 filtering rules.
(See  http://gcn.gsfc.nasa.gov/gcn/tech_describe.html#tc25
for a list of all the filtering functions available.)
If you register, you can have only one client running on the specified
machine (ie the IP Number), because votan uses only the IP Number
to identify you (ie no additional port_number like in original GCN).
Two clients on the same machine have the same IP Number.
Registration is simple -- a 'configuration' is built using the same
GCN/TAN config_builder webpage (see below).
If you choose not to register with votan, there can be no filtering
so then your connection will receive all Notices of all the types
(currently ~2000 per day; this does not count the 1440 imalive
transport-protocol messages sent per day).

SEE ALSO:
GCN has been distributing VOEvents using its own GCN-custom protocol
(also TCP/IP-based) since June 2009.
Information can be found at
     http://gcn.gsfc.nasa.gov/tech_describe.html#tc17
And for the email-based VOEvent distribution:
     http://gcn.gsfc.nasa.gov/tech_describe.html#tc18a
These 2 distribution methods will continue (to support existing customers).

ACTION ITEM:
a) If, after reviewing the information above/below, you want to receive
the GCN/TAN VOEvents, you need to decide if you want to have the filtering
capabilities or not.
If you want filtering, then go to:
     http://gcn.gsfc.nasa.gov/gcn/config_builder.html
and select "#1 Create a new config" specifying the "VOEVENT2.0" or "VOEVENT1.1" selections
in the Distribution method pull-down menu (plus making selections for all
the other items that make up sites's configuration);
or select "#2 Modify an existing config" and (at the least) change your current
distribution method to the VO_EVENT method.
Of course, if you do not want filtering, then you can just connect anonymously[2]
to the server and receive all Notices the GCN/TAN produces.
b) Then you need to get a client (either voevent_client_demo or another client program)
and connect to one of the VOEvent servers listed above.
If you do not want filtering, then just connect with a client program.

Sincerely,
Scott

Scott Barthelmy                      NASA-GSFC, Code 661, Greenbelt, MD  20771
PHONE:  301-286-3106                 (office)       CELL:   301-346-3733
EMAIL:  scott at lheamail.gsfc.nasa.gov
PAGER:  3013463733 at cingularme.com
WEB:    http://gcn.gsfc.nasa.gov/gcn

FOOTNOTES:
[1]  Actually, "anonymously" means without any prior arrangements,
no configuration set-ups, nor any entry to some "allowed to connect" list.
In practice, the GCN/TAN server will always be able to obtain your IP Number
when you connect (with or without a prior configuration set-up).

[2]  Connecting anonymously means you do not -- can not -- have a VOEvent-based entry
in the sites.cfg file.  Every new connection has its IP_Num checked against
those in the sites.cfg file.  If there is a match, then the connection immediately
converts from anonymous to vetted (your identity and configuration are known and used).

//////////////////////////// YOUR CONFIGURATION /////////////////////////////
BEGIN_SITE
SITE_NAME  VSNET
DATES      25jun05   23oct07
SITE_LON_LAT   135.75   35.00
DIST_METHOD   EMAIL
DIST_ADDRESS  vsnet-grb at ooruri.kusastro.kyoto-u.ac.jp
POC_NAME      Daisaku Nogami
POC_ADDRESS   vsnet-grb at ooruri.kusastro.kyoto-u.ac.jp
DAILY_REPORT_ENABLE   0
DAILY_REPORT_ADDRESS  vsnet-grb at ooruri.kusastro.kyoto-u.ac.jp
# Site-specific items:
TRIGGER_ID     0
INTENSITY      -1.0
ERROR          360.1000
DELAY          999.9
SIGNIFICANCE   0.00
CONF_LEVEL     0.00
OBSERVABILITY  ALL
ATTACHMENT     NONE
SIMBAD_NED     0
# Type-specific items:
IPN_POS
INTEGRAL_SPIACS
INTEGRAL_WAKEUP
INTEGRAL_REFINED
INTEGRAL_OFFLINE
SWIFT_BAT_GRB_ALERT
SWIFT_BAT_GRB_POS  trig_id=0
SWIFT_BAT_GRB_NACK_POS
SWIFT_BAT_GRB_LC  trig_id=0
SWIFT_FOM_2OBS  trig_id=0
SWIFT_SC_2SLEW  trig_id=0
SWIFT_XRT_POS
SWIFT_XRT_NACK_POS
SWIFT_XRT_IMAGE
SWIFT_XRT_PROC_IMAGE
SWIFT_UVOT_POS  inten=99.00
SWIFT_UVOT_IMAGE
SWIFT_UVOT_PROC_IMAGE
SWIFT_UVOT_SRCLIST
SWIFT_UVOT_PROC_SRCLIST
SWIFT_POINTDIR
SWIFT_TOO_FOM
SWIFT_TOO_SLEW
END_SITE