GROUP_REQ structure (ws2ipdef.h)

The GROUP_REQ structure provides multicast group information for IPv6 or IPv4 addresses.

Syntax

typedef struct group_req {
  ULONG            gr_interface;
  SOCKADDR_STORAGE gr_group;
} GROUP_REQ, *PGROUP_REQ;

Members

gr_interface

The interface index of the local interface on which the multicast group should be joined or dropped.

gr_group

The address of the multicast group. This may be either an IPv6 or IPv4 multicast address.

Remarks

The GROUP_REQ structure is used with either IPv6 or IPv4 multicast addresses. The GROUP_REQ structure is used with the MCAST_JOIN_GROUP and MCAST_LEAVE_GROUP socket options.

The GROUP_REQ structure and related structures used for multicast programming are based on IETF recommendations in sections 5 and 8.2 of RFC 3768. For more information, see http://www.ietf.org/rfc/rfc3678.txt.

On Windows Vista and later, a set of socket options are available for multicast programming that support IPv6 and IPv4 addresses. These socket options are IP agnostic and can be used on both IPv6 and IPv4. These IP agnostic options use the GROUP_REQ and the GROUP_SOURCE_REQ structures and are the preferred socket options for multicast programming on Windows Vista and later.

The GetAdaptersAddresses function can be used to obtain interface index information required for the gr_interface member.

The GROUP_REQ structure and the socket options that use this structure are only valid on datagram and raw sockets (the socket type must be SOCK_DGRAM or SOCK_RAW).

The GROUP_REQ structure is defined in the Ws2ipdef.h header file which is automatically included in the Ws2tcpip.h header file. The Ws2ipdef.h header files should never be used directly.

Requirements

See also

GROUP_FILTER

GROUP_SOURCE_REQ

GetAdaptersAddresses

Multicast Programming

SOCKADDR_STORAGE

Socket Options

ip_mreq

ipv6_mreq