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>Sockets</TITLE
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>Sockets</TITLE
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><H1
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><A
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><A
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NAME="FILEIO-SOCKETS">Chapter 26. Sockets</H1
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NAME="FILEIO-SOCKETS">Chapter 26. Sockets</H1
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><P
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><P
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>If a network stack is present, then the FILEIO infrastructure also
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>If a network stack is present, then the FILEIO infrastructure also
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provides access to the standard BSD socket calls.</P
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provides access to the standard BSD socket calls.</P
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><P
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><P
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>The netstack table contains entries which describe the network
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>The netstack table contains entries which describe the network
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protocol stacks that are in the system image. Each resident stack
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protocol stacks that are in the system image. Each resident stack
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should export an entry to this table using the
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should export an entry to this table using the
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<TT
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<TT
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CLASS="LITERAL"
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CLASS="LITERAL"
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>NSTAB_ENTRY()</TT
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>NSTAB_ENTRY()</TT
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> macro.</P
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> macro.</P
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><P
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><P
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>Each table entry has the following structure:</P
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>Each table entry has the following structure:</P
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><TABLE
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><TABLE
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BORDER="5"
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BORDER="5"
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BGCOLOR="#E0E0F0"
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BGCOLOR="#E0E0F0"
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WIDTH="70%"
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WIDTH="70%"
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><TR
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><TR
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><TD
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><TD
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><PRE
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><PRE
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CLASS="PROGRAMLISTING"
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CLASS="PROGRAMLISTING"
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>struct cyg_nstab_entry
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>struct cyg_nstab_entry
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{
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{
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cyg_bool valid; // true if stack initialized
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cyg_bool valid; // true if stack initialized
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cyg_uint32 syncmode; // synchronization protocol
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cyg_uint32 syncmode; // synchronization protocol
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char *name; // stack name
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char *name; // stack name
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char *devname; // hardware device name
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char *devname; // hardware device name
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CYG_ADDRWORD data; // private data value
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CYG_ADDRWORD data; // private data value
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|
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int (*init)( cyg_nstab_entry *nste );
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int (*init)( cyg_nstab_entry *nste );
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int (*socket)( cyg_nstab_entry *nste, int domain, int type,
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int (*socket)( cyg_nstab_entry *nste, int domain, int type,
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int protocol, cyg_file *file );
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int protocol, cyg_file *file );
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};</PRE
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};</PRE
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></TD
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></TD
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></TR
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></TR
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></TABLE
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></TABLE
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><P
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><P
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>This table is analogous to a combination of the filesystem and mount
|
>This table is analogous to a combination of the filesystem and mount
|
tables.</P
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tables.</P
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><P
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><P
|
>The <TT
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>The <TT
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CLASS="STRUCTFIELD"
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CLASS="STRUCTFIELD"
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><I
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><I
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>valid</I
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>valid</I
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></TT
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></TT
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> field is set
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> field is set
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<TT
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<TT
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CLASS="LITERAL"
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CLASS="LITERAL"
|
>true</TT
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>true</TT
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> if the stack's <TT
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> if the stack's <TT
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CLASS="FUNCTION"
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CLASS="FUNCTION"
|
>init()</TT
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>init()</TT
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>
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>
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function returned successfully and the
|
function returned successfully and the
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<TT
|
<TT
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CLASS="STRUCTFIELD"
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CLASS="STRUCTFIELD"
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><I
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><I
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>syncmode</I
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>syncmode</I
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></TT
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></TT
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> field contains the
|
> field contains the
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<TT
|
<TT
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CLASS="LITERAL"
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CLASS="LITERAL"
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>CYG_SYNCMODE_SOCK_*</TT
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>CYG_SYNCMODE_SOCK_*</TT
|
> bits described above.</P
|
> bits described above.</P
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><P
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><P
|
>The <TT
|
>The <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
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><I
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>name</I
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>name</I
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></TT
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></TT
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> field contains the name of the
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> field contains the name of the
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protocol stack.</P
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protocol stack.</P
|
><P
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><P
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>The <TT
|
>The <TT
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CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
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><I
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>devname</I
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>devname</I
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></TT
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></TT
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> field names the device that the stack is using. This may
|
> field names the device that the stack is using. This may
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reference a device under "/dev", or may be a name that is only
|
reference a device under "/dev", or may be a name that is only
|
meaningful to the stack itself.</P
|
meaningful to the stack itself.</P
|
><P
|
><P
|
>The <TT
|
>The <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>init()</TT
|
>init()</TT
|
> function pointer is called during
|
> function pointer is called during
|
system initialization to start the protocol stack running. If it
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system initialization to start the protocol stack running. If it
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returns non-zero the <TT
|
returns non-zero the <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
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><I
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>valid</I
|
>valid</I
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></TT
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></TT
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> field is set
|
> field is set
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false and the stack will be ignored subsequently.</P
|
false and the stack will be ignored subsequently.</P
|
><P
|
><P
|
>The <TT
|
>The <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>socket()</TT
|
>socket()</TT
|
> function is called to attempt to create a socket in the
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> function is called to attempt to create a socket in the
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stack. When the <TT
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stack. When the <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>socket()</TT
|
>socket()</TT
|
> API function is called the netstack table is
|
> API function is called the netstack table is
|
scanned and for each valid entry the <TT
|
scanned and for each valid entry the <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>socket()</TT
|
>socket()</TT
|
>
|
>
|
function pointer is called. If
|
function pointer is called. If
|
this returns non-zero then the scan continues to the next valid stack,
|
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.</P
|
or terminates with an error if the end of the table is reached.</P
|
><P
|
><P
|
>The result of a successful socket call is an initialized file object
|
>The result of a successful socket call is an initialized file object
|
with the <TT
|
with the <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>f_xops</I
|
>f_xops</I
|
></TT
|
></TT
|
> field pointing to the
|
> field pointing to the
|
following structure:</P
|
following structure:</P
|
><TABLE
|
><TABLE
|
BORDER="5"
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BORDER="5"
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BGCOLOR="#E0E0F0"
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BGCOLOR="#E0E0F0"
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WIDTH="70%"
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WIDTH="70%"
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><TR
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><TR
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><TD
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><TD
|
><PRE
|
><PRE
|
CLASS="PROGRAMLISTING"
|
CLASS="PROGRAMLISTING"
|
>struct cyg_sock_ops
|
>struct cyg_sock_ops
|
{
|
{
|
int (*bind) ( cyg_file *fp, const sockaddr *sa, socklen_t len );
|
int (*bind) ( cyg_file *fp, const sockaddr *sa, socklen_t len );
|
int (*connect) ( 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,
|
int (*accept) ( cyg_file *fp, cyg_file *new_fp,
|
struct sockaddr *name, socklen_t *anamelen );
|
struct sockaddr *name, socklen_t *anamelen );
|
int (*listen) ( cyg_file *fp, int len );
|
int (*listen) ( cyg_file *fp, int len );
|
int (*getname) ( cyg_file *fp, sockaddr *sa, socklen_t *len, int peer );
|
int (*getname) ( cyg_file *fp, sockaddr *sa, socklen_t *len, int peer );
|
int (*shutdown) ( cyg_file *fp, int flags );
|
int (*shutdown) ( cyg_file *fp, int flags );
|
int (*getsockopt)( cyg_file *fp, int level, int optname,
|
int (*getsockopt)( cyg_file *fp, int level, int optname,
|
void *optval, socklen_t *optlen);
|
void *optval, socklen_t *optlen);
|
int (*setsockopt)( cyg_file *fp, int level, int optname,
|
int (*setsockopt)( cyg_file *fp, int level, int optname,
|
const void *optval, socklen_t optlen);
|
const void *optval, socklen_t optlen);
|
int (*sendmsg) ( cyg_file *fp, const struct msghdr *m,
|
int (*sendmsg) ( cyg_file *fp, const struct msghdr *m,
|
int flags, ssize_t *retsize );
|
int flags, ssize_t *retsize );
|
int (*recvmsg) ( cyg_file *fp, struct msghdr *m,
|
int (*recvmsg) ( cyg_file *fp, struct msghdr *m,
|
socklen_t *namelen, ssize_t *retsize );
|
socklen_t *namelen, ssize_t *retsize );
|
};</PRE
|
};</PRE
|
></TD
|
></TD
|
></TR
|
></TR
|
></TABLE
|
></TABLE
|
><P
|
><P
|
>It should be obvious from the names of these functions which API calls
|
>It should be obvious from the names of these functions which API calls
|
they provide support for. The <TT
|
they provide support for. The <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>getname()</TT
|
>getname()</TT
|
> function
|
> function
|
pointer provides support for both <TT
|
pointer provides support for both <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>getsockname()</TT
|
>getsockname()</TT
|
>
|
>
|
and <TT
|
and <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>getpeername()</TT
|
>getpeername()</TT
|
> while the
|
> while the
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>sendmsg()</TT
|
>sendmsg()</TT
|
> and <TT
|
> and <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>recvmsg()</TT
|
>recvmsg()</TT
|
>
|
>
|
function pointers provide support for <TT
|
function pointers provide support for <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>send()</TT
|
>send()</TT
|
>,
|
>,
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>sendto()</TT
|
>sendto()</TT
|
>, <TT
|
>, <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>sendmsg()</TT
|
>sendmsg()</TT
|
>,
|
>,
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>recv()</TT
|
>recv()</TT
|
>, <TT
|
>, <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>recvfrom()</TT
|
>recvfrom()</TT
|
> and
|
> and
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>recvmsg()</TT
|
>recvmsg()</TT
|
> as appropriate.</P
|
> as appropriate.</P
|
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