APPLETALK(4F)

NAME
appletalk - AppleTalk protocol family

SYNOPSIS
#include <netat/atalk.h>

DESCRIPTION
The AppleTalk protocol family provides basic communications for AppleTalk datagram delivery packetized in Ethernet packets. It provides protocol support only for the SOCK_DGRAM socket type. Other protocols in the suite can be layered atop this facility using the standard socket interfaces.

ADDRESSING
AppleTalk addresses are four-byte quantities, stored in network-standard format (on the Balance and Symmetry series the addresses are word- and byte-reversed). The include file <netat/atalk.h> defines this address as a discriminated union.

Sockets bound to the AppleTalk protocol family utilize the following addressing structure:
struct    sockaddr_at {
    short    at_family;    /* AF_APPLETALK */
    struct a_addr    at_addr;    /* 4 bytes */
    u_char    at_sno;    /* ddp socket number */
    u_char    at_ptype;    /* ddp protocol type */
    char    at_dummy[8];    /* fill */
}; where:
struct    a_addr    {
    union    {
    struct    {
    u_short    Net;
    u_char    Node;
    u_char    Abridge;
        } at_chrs;
    long    Addr;
    } at_un; };
#define    at_Net    at_un.at_chrs.Net
#define    at_Node    at_un.at_chrs.Node
#define    at_Abridge    at_un.at_chrs.Abridge
#define    at_adr    at_un.Addr
Sockets may be created with the address at_Net and at_Node equal to zero (0) to effect “wildcard” matching on incoming messages. A connect() that specifies at_Net and at_Node equal to zero (0) returns the current values for the host.

PROTOCOLS
The AppleTalk protocol family consists of the Datagram Delivery Protocol (DDP) only. It is used to support the SOCK_DGRAM abstraction.

SEE ALSO
ddp(4P)