Software:ConfigureEvents - MdsWiki
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MDSplus events allow processes to wait for a named occurrence that is generated by another application. Users can specify MDSplus events in graphics applications such as dwscope and jScope which would signal that the data required for the plot is now available so that these plots will update automatically.

Originally the MDSplus event system utilized a client/server approach for transmitting events to other systems on both the local area network and the wide are network. The more recent MDSplus event system uses udp multicast packets for broadcasting events on the local area network. This is much more efficient and less prone to lock ups due to misbehaving client applications. There are several environment variables that will effect the behavior of event communications listed in the table below.

Environment Variable Description Default
UDP_EVENTS Turns on the use of udp multicast events for LAN transmission. If defined (any value) udp events will be used. If this UDP_EVENTS environment variables is not set then named pipes are used on the local system unless the mds_event_target or mds_event_server environment variables are set. "yes"
mds_event_target If defined, any application that sets/issues an MDSplus event will connect to the host and port specified in the environment variable and the remote connection will issue the event using the method configured by environment variables on that remote system. For example, setting mds_event_target to myhost:8010 will cause an application setting an event to connect to myhost on port 8010 and have the mdsip server on the remote end issue the event on the clients behalf. Not set
mds_event_server If defined, any application that waits for an MDSplus event will connect to the host and port specified in the environment variable and wait for the event using the method configured by environment variables on that remote system. For example, setting mds_event_server to myhost (if no port specified it defaults to port 8000) will cause an application waiting for event notification to connect to myhost and have the mdsip server on the remote end wait for the event on the clients behalf. Not set
mdsevent_address If defined it must define a multicast address range to use for broadcasting MDSplus events on the local area network. The format of the string for the environment variable is n1.n2.n3.n4-n5. For example, if the mdsevent_address environment variable is set to 224.0.10.10-20, addresses 224.0.10.10, 224.0.10.11,...,224.0.10.20 will be used for transmission of MDSplus events. The choice of the last digit value in the ipv4 address is based on a hash of the event name. Note: Multicast address ranges are limited so before you set this environment variable you should look at theIPv4 Multicast Address Space Registry for possible addresses. Network routers and switches only pass certain multicast packets based on the address used. Whether you use the default address or override it with this environment variable, you should make sure your system firewall and local network switches permit the transmission of packets to these addresses. If this environment variable is not define and UDP_EVENTS is set then events are transmitted using the address 224.0.0.175.
mdsevent_port If defined, it specifies the port number used for transmitting events. If not defined, port 4000 is used.