TO: GCN/TAN people interested in VOEvents RE: VOEvent Version 2.0 is available DT: 22 Apr 2012 INTRODUCTION: Recall that last month GCN/TAN started distributing VOEvents via 3 different servers ( http://gcn.gsfc.nasa.gov/gcn/admin/voevent_server_announce.txt ). Those 3 servers were distributing Version 1.1 VOEvents. Now one of the servers (eApps) has been converted to distribute Version 2.0 VOEvents (now the current IVOA VOEvent version): SERVERS ORIGINAL CONFIG NEW CONFIG VERSIONS VERSIONS 209.208.78.170 (Atlantic.net) 1.1 1.1 50.116.49.68 (Linode.com) 1.1 1.1 68.169.57.253 (eApps.com) 1.1 2.0 The connection IP_Numbers, port numbers, and read/write protocol all stay the same for the new 2.0 version. Only the schema reference changes; and even that is only in the url pointing to the 2.0 schema -- the contents/formats of the actual "data" stay the same. (For most of you, even that schema change will not affect you.) There are redundant servers for the Ver 1.1 events, but no redundancy (as yet) for the Ver 2.0 events. All GCN/TAN notice types are available on all 3 servers; only the version is different. (That is 15 GRB_Position notice types, 7 Transient_Position types, 15 non-position types (lc, images, spectra), 4 spacecraft pointing_direction types, and 7 Test types.) Version 1.1 events have been available within GCN/TAN since June 2009. As such, a community of 1.1 users has developed. GCN/TAN policy has grandfather-ed in ver 1.1 for all distribution methods and formats forever. If the population of 2.0 users overtakes the 1.1 users (ratio is currently 1 to 3), then one of remaining 1.1 servers will be converted to 2.0 (but there will always be a 1.1 server until at least a year past the last 1.1 user connection). If it does not matter to the Ver1.1 customer, they are encouraged to change their configuration to version 2.0, so that I can better/sooner know when to adjust the balance of the 1.1 vs 2.0 servers and when the last of the version 1.1 customers is gone. VOEVENT SPECIFICATION: The IVOA docuement on Version 2.0 VOEvents can be found at: http://www.ivoa.net/Documents/VOEvent/index.html . Version 2.0 is the current version for VOEvents within the IVOA. OTHER DISTRIBUTION METHODS: Just like the Ver 1.1, the Ver 2.0 VOEvents are also available via the GCN/TAN-custom VOEvent sockets and by email (both in the body of the email and as an attachment). EXCERPTS FROM THE ORIGINAL/MARCH VOEVENT ANNOUNCEMENT: 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. To run this demo, the commandline is: voevent_client_demo examples: voevent_client_demo 209.208.78.170 8099 All 3 servers are listening on port 8089 for incoming connections: 209.208.78.170 (on Atlantic.net cloud service) (Ver 1.1) 50.116.49.68 (on Linode.com cloud service) (Ver 1.1) 68.169.57.253 (on eApps.com cloud service) (Ver 2.0) 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 GCN/TAN votan is a server and you can connect anonymously, 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, 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). 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 "VO_EVENT" selection 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 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 progrqam. THE FUTURE: The following items/functions will be implemented in the future (in semi-prioritized order): a) Add version 2.0. DONE. b) Add capability for vetted authors to publish to these servers. c) Allowing anonymous connections to publish. d) Having a database of past VOEvents that is queriable. Sincerely, Scott Scott Barthelmy NASA-GSFC, Code 661, Greenbelt, MD 20771 PHONE: 301-286-3106 (office) CELL: 301-346-3733 EMAIL: scott@lheamail.gsfc.nasa.gov PAGER: 3013463733@cingularme.com WEB: http://gcn.gsfc.nasa.gov/gcn (You can take this opportunity to review your current configuration and request changes (see http://gcn.gsfc.nasa.gov/gcn/config_builder.html Selection #2) or your can just tell me what you want changed, but please include your config below so (a) I know your site_name, and (b) you mark the differences/changes.)