socklib.html

Vxworks API操作系统和驱动程序设计API。压缩的HTML文件

</blockQuote><h4>IP_TTL-- set the time-to-live field in outgoing datagrams</h4><blockQuote>
Sets the Time-To-Live field for each packet sent from this socket.
<pre>    setsockopt (sock, IPPROTO_IP, IP_TTL, &amp;optval, sizeof(optval));
</pre>
Here <i>optval</i> is an integer (type <i>int</i>), indicating the number of hops
a packet can take before it is discarded.
<p>
</blockQuote><h4>IP_RECVRETOPTS -- [un-]set queueing of reversed source route</h4><blockQuote>
Sets whether or not reversed source route queueing will be enabled for
incoming datagrams. (Not implemented)
<pre>    setsockopt (sock, IPPROTO_IP, IP_RECVRETOPTS, &amp;optval, sizeof(optval));
</pre>
Here <i>optval</i> is a boolean (type <i>int</i>).  However, this option is
currently not implemented, so setting it will not change the behavior
of the system.
<p>
</blockQuote><h4>IP_RECVDSTADDR -- [un-]set queueing of IP destination address</h4><blockQuote>
Sets whether or not the socket will receive the IP address of the
destination of an incoming datagram in control data.
<pre>    setsockopt (sock, IPPROTO_IP, IP_RECVDSTADDR, &amp;optval, sizeof(optval));
</pre>
Here <i>optval</i> is a boolean (type <i>int</i>).
<p>
</blockquote><h4>OPTIONS FOR BOTH STREAM AND DATAGRAM SOCKETS</h4><blockquote><p>
The following sections describe options that can be used with either
stream or datagram sockets.
<p>
</blockQuote><h4>SO_REUSEADDR -- Reusing a Socket Address</h4><blockQuote>
Specify the <b>SO_REUSEADDR</b> option to bind a stream socket to a local
port that may be still bound to another stream socket:
<pre>    setsockopt (sock, SOL_SOCKET, SO_REUSEADDR, &amp;optval, sizeof (optval));
</pre>
The value at <i>optval</i> is an integer (type <i>int</i>), either 1 (on) or 0
(off).
<p>
When the <b>SO_REUSEADDR</b> option is turned on, applications may bind a stream 
socket to a local port. This is possible even if the port is still bound 
to another stream socket.  It is even  possible if that other socket is 
associated with a "zombie" protocol control block context that has not yet 
freed from previous sessions.  The uniqueness of port number combinations 
for each connection is still preserved through sanity checks performed at 
actual connection setup time.  If this option is not turned on and an 
application attempts to bind to a port that is being used by a zombie 
protocol control block, the <b><a href="./sockLib.html#bind">bind</a>(&nbsp;)</b> call fails.
<p>
</blockQuote><h4>SO_REUSEPORT -- Reusing a Socket address and port</h4><blockQuote>
This option is similar to the <b>SO_REUSEADDR</b> option but it allows binding to
the same local address and port combination. 
<pre>    setsockopt (sock, SOL_SOCKET, SO_REUSEPORT, &amp;optval, sizeof (optval));
</pre>
The value at <i>optval</i> is an integer (type <i>int</i>), either 1 (on) or 0 (off).
<p>
The <b>SO_REUSEPORT</b> option is mainly required by multicast applications where
a number of applications need to bind to the same multicast address and port
to receive multicast data. Unlike <b>SO_REUSEADDR</b> where only the later
applications need to set this option, with <b>SO_REUSEPORT</b> all applications
including the first to bind to the port are required to set this option. For
multicast addresses <b>SO_REUSEADDR</b> and <b>SO_REUSEPORT</b> show the same behavior so
<b>SO_REUSEADDR</b> can be used instead. 
<p>
</blockQuote><h4>SO_SNDBUF -- Specifying the Size of the Send Buffer</h4><blockQuote>
Specify the <b>SO_SNDBUF</b> option to adjust the maximum size of the
socket-level send buffer:
<pre>    setsockopt (sock, SOL_SOCKET, SO_SNDBUF, &amp;optval, sizeof (optval));
</pre>
The value at <i>optval</i> is an integer (type <b>int</b>) that specifies the
size of the socket-level send buffer to be allocated.
<p>
When stream or datagram sockets are created, each transport protocol
reserves a set amount of space at the socket level for use when the
sockets are attached to a protocol.  For TCP, the default size of
the send buffer is 8192 bytes.  For UDP, the default size of the
send buffer is 9216 bytes.  Socket-level buffers are allocated
dynamically from the mbuf pool.
<p>
The effect of setting the maximum size of buffers (for both <b>SO_SNDBUF</b> and 
<b>SO_RCVBUF</b>, described below) is not actually to allocate the mbufs from 
the mbuf pool.  Instead, the effect is to set the high-water mark in the 
protocol data structure, which is used later to limit the amount of mbuf 
allocation.  Thus, the maximum size specified for the socket level send 
and receive buffers can affect the performance of bulk data transfers.  
For example, the size of the TCP receive windows is limited by the 
remaining socket-level buffer space.  These parameters must be adjusted 
to produce the optimal result for a given application.
<p>
</blockQuote><h4>SO_RCVBUF -- Specifying the Size of the Receive Buffer</h4><blockQuote>
Specify the <b>SO_RCVBUF</b> option to adjust the maximum size of the
socket-level receive buffer:
<pre>    setsockopt (sock, SOL_SOCKET, SO_RCVBUF, &amp;optval, sizeof (optval));
</pre>
The value at <i>optval</i> is an integer (type <b>int</b>) that specifies the
size of the socket-level receive buffer to be allocated.
<p>
When stream or datagram sockets are created, each transport protocol
reserves a set amount of space at the socket level for use when the
sockets are attached to a protocol.  For TCP, the default size is
8192 bytes.  UDP reserves 41600 bytes, enough space for up to forty
incoming datagrams (1 Kbyte each).
<p>
See the <b>SO_SNDBUF</b> discussion above for a discussion of the impact of
buffer size on application performance.
<p>
</blockQuote><h4>SO_OOBINLINE -- Placing Urgent Data in the Normal Data Stream</h4><blockQuote>
Specify the <b>SO_OOBINLINE</b> option to place urgent data within the
normal receive data stream:
<pre>    setsockopt (sock, SOL_SOCKET, SO_OOBINLINE, &amp;optval, sizeof (optval));
</pre>
TCP provides an expedited data service that does not conform to the
normal constraints of sequencing and flow control of data
streams. The expedited service delivers "out-of-band" (urgent) data
ahead of other "normal" data to provide interrupt-like services (for
example, when you hit a CTRL-C during telnet or rlogin session while
data is being displayed on the screen.)
<p>
TCP does not actually maintain a separate stream to support the
urgent data.  Instead, urgent data delivery is implemented as a
pointer (in the TCP header) which points to the sequence number of
the octet following the urgent data. If more than one transmission
of urgent data is received from the peer, they are all put into the
normal stream. This is intended for applications that cannot afford
to miss out on any urgent data but are usually too slow to respond
to them promptly.
<p>
</blockquote><h4>RETURNS</h4><blockquote><p>
<p>
OK, or ERROR if there is an invalid socket, an unknown option, an option
length greater than MLEN, insufficient mbufs, or the call is unable to set
the specified option.
</blockquote><h4>SEE ALSO</h4><blockquote><p>
<b><a href="./sockLib.html#top">sockLib</a></b>

<hr>
<a name="getsockopt"></a>
<p align=right>
<a href="rtnIndex.htm"><i>OS Libraries :  Routines</i></a></p>

</blockquote><h1>getsockopt(&nbsp;)</h1> <blockquote></a></blockquote><h4>NAME</h4><blockquote>  
<p><strong>getsockopt(&nbsp;)</strong> - get socket options</p>

</blockquote><h4>SYNOPSIS</h4><blockquote><p>
<pre>STATUS getsockopt
    (
    int    s,                 /* socket */
    int    level,             /* protocol level for options */
    int    optname,           /* name of option */
    char * optval,            /* where to put option */
    int *  optlen             /* where to put option length */
    )
</pre>

</blockquote><h4>DESCRIPTION</h4><blockquote><p>
This routine returns relevant option values associated with a socket.
To manipulate options at the "socket" level, <i>level</i> should be <b>SOL_SOCKET</b>.
Any other levels should use the appropriate protocol number.
The <i>optlen</i> parameter should be initialized to indicate the amount of
space referenced by <i>optval</i>.  On return, the value of the option is copied to
<i>optval</i> and the actual size of the option is copied to <i>optlen</i>.
<p>
Although <i>optval</i> is passed as a char *, the actual variable whose address 
gets passed in should be an integer or a structure, depending on which 
<i>optname</i> is being passed. Refer to <b><a href="./sockLib.html#setsockopt">setsockopt</a>(&nbsp;)</b> to determine the correct 
type of the actual variable (whose address should then be cast to a char *).
<p>
</blockquote><h4>RETURNS</h4><blockquote><p>
<p>
OK, or ERROR if there is an invalid socket, an unknown option, or the call
is unable to get the specified option.
<p>
</blockquote><h4>EXAMPLE</h4><blockquote><p>
Because <b>SO_REUSEADDR</b> has an integer parameter, the variable to be
passed to <b><a href="./sockLib.html#getsockopt">getsockopt</a>(&nbsp;)</b> should be declared as
<pre>   int reuseVal;
</pre>
and passed in as 
<pre>   (char *)&amp;reuseVal.
</pre>
Otherwise the user might mistakenly declare <b>reuseVal</b> as a character,
in which case <b><a href="./sockLib.html#getsockopt">getsockopt</a>(&nbsp;)</b> will only return the first byte of the
integer representing the state of this option.  Then whether the return
value is correct or always 0 depends on the endian-ness of the machine.
<p>
</blockquote><h4>SEE ALSO</h4><blockquote><p>
<b><a href="./sockLib.html#top">sockLib</a></b>, <b><a href="./sockLib.html#setsockopt">setsockopt</a>(&nbsp;)</b>

<hr>
<a name="getsockname"></a>
<p align=right>
<a href="rtnIndex.htm"><i>OS Libraries :  Routines</i></a></p>

</blockquote><h1>getsockname(&nbsp;)</h1> <blockquote></a></blockquote><h4>NAME</h4><blockquote>  
<p><strong>getsockname(&nbsp;)</strong> - get a socket name</p>

</blockquote><h4>SYNOPSIS</h4><blockquote><p>
<pre>STATUS getsockname
    (
    int               s,      /* socket descriptor */
    struct sockaddr * name,   /* where to return name */
    int *             namelen /* space available in name, later filled in */
                              /* with actual name size */ 
    )
</pre>

</blockquote><h4>DESCRIPTION</h4><blockquote><p>
This routine gets the current name for the specified socket <i>s</i>.
The <i>namelen</i> parameter should be initialized to indicate the amount of
space referenced by <i>name</i>.  On return, the name of the socket is copied to
<i>name</i> and the actual size of the socket name is copied to <i>namelen</i>.
<p>
</blockquote><h4>RETURNS</h4><blockquote><p>
OK, or ERROR if the socket is invalid.
</blockquote><h4>SEE ALSO</h4><blockquote><p>
<b><a href="./sockLib.html#top">sockLib</a></b>

<hr>
<a name="getpeername"></a>
<p align=right>
<a href="rtnIndex.htm"><i>OS Libraries :  Routines</i></a></p>

</blockquote><h1>getpeername(&nbsp;)</h1> <blockquote></a></blockquote><h4>NAME</h4><blockquote>  
<p><strong>getpeername(&nbsp;)</strong> - get the name of a connected peer</p>

</blockquote><h4>SYNOPSIS</h4><blockquote><p>
<pre>STATUS getpeername
    (
    int               s,      /* socket descriptor */
    struct sockaddr * name,   /* where to put name */
    int *             namelen /* space available in name, later filled in */
                              /* with actual name size */ 
    )
</pre>

</blockquote><h4>DESCRIPTION</h4><blockquote><p>
This routine gets the name of the peer connected to socket <i>s</i>.
The <i>namelen</i> parameter should be initialized to indicate the amount of
space referenced by <i>name</i>.  On return, the name of the socket is copied to
<i>name</i> and the actual size of the socket name is copied to <i>namelen</i>.
<p>
</blockquote><h4>RETURNS</h4><blockquote><p>
OK, or ERROR if the socket is invalid
or not connected.
</blockquote><h4>SEE ALSO</h4><blockquote><p>
<b><a href="./sockLib.html#top">sockLib</a></b>

<hr>
<a name="shutdown"></a>
<p align=right>
<a href="rtnIndex.htm"><i>OS Libraries :  Routines</i></a></p>

</blockquote><h1>shutdown(&nbsp;)</h1> <blockquote></a></blockquote><h4>NAME</h4><blockquote>  
<p><strong>shutdown(&nbsp;)</strong> - shut down a network connection</p>

</blockquote><h4>SYNOPSIS</h4><blockquote><p>
<pre>STATUS shutdown
    (
    int s,                    /* socket to shut down */
    int how                   /* 0 = receives disallowed 1 = sends */
                              /* disallowed 2 = sends and receives */
                              /* disallowed */ 
    )
</pre>

</blockquote><h4>DESCRIPTION</h4><blockquote><p>
This routine shuts down all, or part, of a connection-based socket <i>s</i>.
If the value of <i>how</i> is 0, receives are disallowed.  If <i>how</i> is 1,
sends are disallowed.  If <i>how</i> is 2, both sends and receives are
disallowed.
<p>
</blockquote><h4>RETURNS</h4><blockquote><p>
ERROR if the socket is invalid or has no registered
socket-specific routines; otherwise <b><a href="./sockLib.html#shutdown">shutdown</a>(&nbsp;)</b> returns the return value
from the socket-specific shutdown routine (typically OK in the case of
a successful shutdown or ERROR otherwise).
</blockquote><h4>SEE ALSO</h4><blockquote><p>
<b><a href="./sockLib.html#top">sockLib</a></b>

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