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| <h4 class="subsection">16.8.1 Creating a Socket</h4> |
| |
| <p><a name="index-creating-a-socket-1772"></a><a name="index-socket_002c-creating-1773"></a><a name="index-opening-a-socket-1774"></a> |
| The primitive for creating a socket is the <code>socket</code> function, |
| declared in <samp><span class="file">sys/socket.h</span></samp>. |
| <a name="index-sys_002fsocket_002eh-1775"></a> |
| <!-- sys/socket.h --> |
| <!-- BSD --> |
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| <div class="defun"> |
| — Function: int <b>socket</b> (<var>int namespace, int style, int protocol</var>)<var><a name="index-socket-1776"></a></var><br> |
| <blockquote><p>This function creates a socket and specifies communication style |
| <var>style</var>, which should be one of the socket styles listed in |
| <a href="Communication-Styles.html#Communication-Styles">Communication Styles</a>. The <var>namespace</var> argument specifies |
| the namespace; it must be <code>PF_LOCAL</code> (see <a href="Local-Namespace.html#Local-Namespace">Local Namespace</a>) or |
| <code>PF_INET</code> (see <a href="Internet-Namespace.html#Internet-Namespace">Internet Namespace</a>). <var>protocol</var> |
| designates the specific protocol (see <a href="Socket-Concepts.html#Socket-Concepts">Socket Concepts</a>); zero is |
| usually right for <var>protocol</var>. |
| |
| <p>The return value from <code>socket</code> is the file descriptor for the new |
| socket, or <code>-1</code> in case of error. The following <code>errno</code> error |
| conditions are defined for this function: |
| |
| <dl> |
| <dt><code>EPROTONOSUPPORT</code><dd>The <var>protocol</var> or <var>style</var> is not supported by the |
| <var>namespace</var> specified. |
| |
| <br><dt><code>EMFILE</code><dd>The process already has too many file descriptors open. |
| |
| <br><dt><code>ENFILE</code><dd>The system already has too many file descriptors open. |
| |
| <br><dt><code>EACCES</code><dd>The process does not have the privilege to create a socket of the specified |
| <var>style</var> or <var>protocol</var>. |
| |
| <br><dt><code>ENOBUFS</code><dd>The system ran out of internal buffer space. |
| </dl> |
| |
| <p>The file descriptor returned by the <code>socket</code> function supports both |
| read and write operations. However, like pipes, sockets do not support file |
| positioning operations. |
| </p></blockquote></div> |
| |
| <p>For examples of how to call the <code>socket</code> function, |
| see <a href="Local-Socket-Example.html#Local-Socket-Example">Local Socket Example</a>, or <a href="Inet-Example.html#Inet-Example">Inet Example</a>. |
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