SP_MULTICAST(3)			 User Manuals		       SP_MULTICAST(3)

NAME
       SP_multicast,   SP_scat_multicast,  SP_multigroup_multicast,  SP_multi‐
       group_scat_multicast - Multicast message to groups

SYNOPSIS
       #include <sp.h>

       int  SP_multicast(  mailbox  mbox,  service  service_type,  const  char
       *group, int16 mess_type, int mess_len, const char *mess);
       int  SP_scat_multicast(	mailbox mbox, service service_type, const char
       *group, int16 mess_type, const scatter scat_mess);

       int SP_multigroup_multicast( mailbox mbox,  service  service_type,  int
       num_groups,  const  char groups[][MAX_GROUP_NAME], int16 mess_type, int
       mess_len, const char *mess);
       int SP_multigroup_scat_multicast( mailbox mbox,	service	 service_type,
       int  num_groups,	 const char groups[][MAX_GROUP_NAME], int16 mess_type,
       const scatter scat_mess);

DESCRIPTION
       SP_multicast and its variants all can multicast send a message  to  one
       or  more groups.	 The message is sent on a particular connection and is
       marked as having come from  the	connection  who	 sent  it.   The  ser‐
       vice_type  is  a type field that should be set to the service this mes‐
       sage requires. The valid flags for messages are:

	      UNRELIABLE_MESS
	      RELIABLE_MESS
	      FIFO_MESS
	      CAUSAL_MESS
	      AGREED_MESS
	      SAFE_MESS
       This type can be	 bit  ORed  with  other	 flags	like  SELF_DISCARD  if
       desired.	 Currently SELF_DISCARD is the only additional flag.

       If  the	SP_multicast or SP_scat_multicast versions are being used then
       only one group can be sent to. So the group string should  include  the
       name  of	 the  group  to send to. If a multigroup varient is being used
       then the groups are specified by the num_groups integer and  the	 array
       of  group  names	 called groups representing all the groups the message
       should be sent to.  Each group has  a  string  name  of	no  more  then
       MAX_GROUP_NAME  chars.  The  array  should  have at least as many group
       names as the 'num_groups'  parameter indicates.	The Spread system will
       only send the message once but will deliver it to all connections which
       have joined at least one of the groups listed.

       The mess_type This is a SHORT int (16 bits) which can be	 used  by  the
       application  arbitrarily.   The intent is that it could be used to NAME
       different kinds of data messages so they can be differentiated  without
       looking	into  the body of the message.	This value will be endian cor‐
       rected before receiving.

       If the non-scatter varients are being used  then	 a  single  buffer  is
       passed  to  the	multicast call specifying the full message to be sent.
       The mess_len field gives the length in bytes of the message. While  the
       mess  field  is	a pointer to the buffer containing the message.	 For a
       scatter call both of these are replaced with one pointer, scat_mess, to
       a scatter structure, which is just like an iovec.  This allows messages
       made up of several parts to be sent without an extra  copy  on  systems
       which support scatter-gather.

RETURN VALUES
       Returns	the  number  of	 bytes sent on success or one of the following
       errors ( < 0 ):

       ILLEGAL_SESSION
	       The mbox given to multicast on was illegal.

       ILLEGAL_MESSAGE
	       The message had an illegal structure, like a scatter not filled
	       out correctly.

       CONNECTION_CLOSED
	       During communication to send the message errors occured and the
	       send could not be completed.

BUGS
       None.

AUTHOR
       Yair Amir <yairamir@cnds.jhu.edu>
       Jonathan Stanton <jonathan@cnds.jhu.edu>

SEE ALSO
       libspread(3)

SPREAD				   JULY 1998		       SP_MULTICAST(3)

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