Comtrol eCos - Manual (Page 429)

Chapter 26. Sockets
If a network stack is present, then the FILEIO infrastructure also provides access to the standard BSD socket calls.
The netstack table contains entries which describe the network protocol stacks that are in the system image. Each
resident stack should export an entry to this table using the
NSTAB_ENTRY() macro.
Each table entry has the following structure:
struct cyg_nstab_entry
{
cyg_bool valid; // true if stack initialized
cyg_uint32 syncmode; // synchronization protocol
char *name; // stack name
char *devname; // hardware device name
CYG_ADDRWORD data; // private data value
int (*init)( cyg_nstab_entry *nste );
int (*socket)( cyg_nstab_entry *nste, int domain, int type,
int protocol, cyg_file *file );
};
This table is analogous to a combination of the filesystem and mount tables.
The valid field is set true if the stack’s init() function returned successfully and the syncmode field contains
the CYG_SYNCMODE_SOCK_* bits described above.
The name field contains the name of the protocol stack.
The devname field names the device that the stack is using. This may reference a device under "/dev", or may be
a name that is only meaningful to the stack itself.
The init() function pointer is called during system initialization to start the protocol stack running. If it returns
non-zero the valid field is set false and the stack will be ignored subsequently.
The socket() function is called to attempt to create a socket in the stack. When the socket() API function is
called the netstack table is scanned and for each valid entry the socket() function pointer is called. If this returns
non-zero then the scan continues to the next valid stack, or terminates with an error if the end of the table is reached.
The result of a successful socket call is an initialized file object with the f_xops field pointing to the following
structure:
struct cyg_sock_ops
{
int (*bind) ( cyg_file *fp, const sockaddr *sa, socklen_t len );
int (*connect) ( cyg_file *fp, const sockaddr *sa, socklen_t len );
int (*accept) ( cyg_file *fp, cyg_file *new_fp,
struct sockaddr *name, socklen_t *anamelen );
int (*listen) ( cyg_file *fp, int len );
int (*getname) ( cyg_file *fp, sockaddr *sa, socklen_t *len, int peer );
int (*shutdown) ( cyg_file *fp, int flags );
int (*getsockopt)( cyg_file *fp, int level, int optname,
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