Guralp Systems Scream - Manual (Page 55)

User guide
6. To stop the link, right-click as before and select GCFSTOP from
the pop-up menu. If you do not GCFSTOP, the server will
continue to transmit to a client that is no longer listening. You
should ensure that the server replies with a GCFACKN message:
If an acknowledgement does not appear in the Control pane,
repeat the GCFSTOP command.
Scream! automatically issues a GCFSTOP to all connected
servers when it exits.
The steps above can be repeated as many times as necessary to pull
data from several servers. Scream! remembers all the network settings
when it exits, and automatically tries to reconnect when you start it
again.
5.1.1 TCP clients
Clients can also make a TCP connection to Scream! and request data.
Using this method, block re-transmission requests are delegated to the
network protocol stack but there is a significant overhead involved in
keeping the connection active.
Clients using TCP can access the server by its host name as well as by
its IP address. This is useful for installations where the IP address
may change.
5.1.2 Multicast clients
Multicasting is a feature of TCP/IP which allows you to send network
packets to several clients at once. These are most often used on local
networks. Multicast servers use addresses between 224.0.0.0 and
239.255.255.255. CMG-EAMs and CMG-NAMs, for example, always
listen on the multicast address 239.193.15.67. (Mnemonic: 239.193 is
in the privately-assignable block and 1567 is the default scream port.)
When you Add a multicast server, right-clicking on its entry in the
Servers list box pops up a menu with Connect and Disconnect options
in place of the GCFxxxx commands.
Selecting Connect instructs Scream! to join the multicast group with
that address. If the server is running, data should begin appearing
immediately.
Selecting Disconnect makes Scream! leave the multicast group. You
can be in several multicast groups simultaneously, and join or leave
each one independently of the others.
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