Spread - Perl extension for the Spread group communication system

  use Spread;

  # Connect
  my($mailbox, $private_group) = Spread::connect(
        spread_name => '4444@host.domain.com',
        private_name => 'mrcool',
        );

  # Join and leave groups
  my(@group_to_join) = ( 'GroupA', 'GroupB', 'GroupC' );
  my(@joined_groups) = grep( Spread::join($mbox, $_), @group_to_join );
  print "Spread::join -- $sperrorno"
        unless (Spread::leave($mbox, 'GroupC'));

  # Multicast to group(s)
  Spread::multicast($mbox, AGREED_MESS, 'GroupB', 0, "Hey you!");
  Spread::multicast($mbox, SAFE_MESS, @joined_groups, 0, "Hey yall!");

  # Poll mailbox
  my($messsize) = Spread::poll($mbox);
  if(defined($messsize)) { print "Next message: $messsize bytes\n"; }
  else { print "Spread::poll $sperrno\n"; }

  # Receive messages (see spread's man pages for more description)
  my($service_type, $sender, $groups, $mess_type, $endian, $message) =
        Spread::receive($mbox);
  my($service_type, $sender, $groups, $mess_type, $endian, $message) =
        Spread::receive($mbox, 1.789);  # 1.789 second timeout on receive

  # Disconnect
  if(Spread::disconnect($mbox)) { print "Successful disconnect\n"; }
  else { print "Spread::disconnect -- $sperrorno\n"; }

Understanding through practice ;)

See man pages for SP_connect, SP_join, SP_multicast, SP_receive, SP_poll, SP_error, SP_leave, SP_disconnect.

$sperror holds either the integer spread error or a descriptive string depending on the context in which CW$sperror is used.

The predefined groups of exports in the use statements are as follows:

use Spread qw(:SP);

Exports the Spread::connect, Spread::join, Spread::multicast, Spread::receive, Spread::poll, Spread::error, Spread::leave, and Spread::disconnect as SP_connect, SP_join, SP_multicast, SP_receive, SP_poll, SP_error, SP_leave, and SP_disconnect, respectively.

use Spread qw(:ERROR);

Exports all of the error conditions. Please refer to the SP_* C man pages as the RETURN VALUES there have both identical spellings and meanings.

use Spread qw(:MESS);

Exports all of the message types (this is returned as service type by the Spread::receive function and is the request service type of the Spread::multicast function). The actual meaning of these orderings and assurances are not simple to explain without a basic understanding of group communication systems. For more information on this topic, please visit the Spread web site at http://www.spread.org/

All constants in alphabetical order:

  ACCEPT_SESSION
  AGREED_MESS
  BUFFER_TOO_SHORT
  CAUSAL_MESS
  CAUSED_BY_DISCONNECT
  CAUSED_BY_JOIN
  CAUSED_BY_LEAVE
  CAUSED_BY_NETWORK
  CONNECTION_CLOSED
  COULD_NOT_CONNECT
  FIFO_MESS
  HIGH_PRIORITY
  ILLEGAL_GROUP
  ILLEGAL_MESSAGE
  ILLEGAL_SERVICE
  ILLEGAL_SESSION
  ILLEGAL_SPREAD
  LOW_PRIORITY
  MAX_SCATTER_ELEMENTS
  MEDIUM_PRIORITY
  MEMBERSHIP_MESS
  REGULAR_MESS
  REG_MEMB_MESS
  REJECT_ILLEGAL_NAME
  REJECT_NOT_UNIQUE
  REJECT_NO_NAME
  REJECT_QUOTA
  REJECT_VERSION
  RELIABLE_MESS
  SAFE_MESS
  SELF_DISCARD
  TRANSITION_MESS
  UNRELIABLE_MESS

Theo Schlossnagle <jesus@cnds.jhu.edu>

Various spread documentation at http://www.spread.org/.