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<title>getservbyport()--Get Service Name for Port Number</title>
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<h2>getservbyport()--Get Service Name for Port Number</h2>
<div class="box" style="width: 80%;">
<br>
&nbsp;&nbsp;BSD 4.3 Syntax<br>
<pre>
#include &lt;netdb.h&gt;
struct servent *getservbyport(int <em>port_number</em>,
char *<em>protocol_name</em>)
</pre>
<br>
&nbsp;&nbsp;Service Program Name: QSOSRV2<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Default Public Authority: *USE<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Threadsafe: No; see <a href="#USAGE_NOTES">Usage Notes</a>.<br>
<!-- iddvc RMBR -->
<br>
</div>
<br>
<div class="box" style="width: 80%;">
<br>
&nbsp;&nbsp;<a href="_xopen_source.htm">UNIX 98 Compatible Syntax</a><br>
<pre>
#define _XOPEN_SOURCE 520
#include &lt;netdb.h&gt;
struct servent *getservbyport(int <em>port_number</em>,
const char *<em>protocol_name</em>)
</pre>
<br>
&nbsp;&nbsp;Service Program Name: QSOSRV2<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Default Public Authority: *USE<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Threadsafe: No; see <a href="#USAGE_NOTES">Usage Notes</a>.<br>
<!-- iddvc RMBR -->
<br>
</div>
<br>
<p>The <em>getservbyport()</em> function is used to retrieve information about
a service assigned to a port number. The information is retrieved from the
service database file.</p>
<p>There are two versions of the API, as shown above. The base i5/OS API uses BSD 4.3
structures and syntax. The other uses syntax and structures compatible with the UNIX 98
programming interface specifications. You can select the UNIX 98 compatible
interface with the <a href="_xopen_source.htm">_XOPEN_SOURCE</a> macro.</p>
<br>
<h3>Parameters</h3>
<dl>
<dt><strong>port_number</strong></dt>
<dd>(Input) The port number for which service information is to be
retrieved.<br>
<br>
</dd>
<dt><strong>protocol_name</strong></dt>
<dd>(Input) The pointer to the character string that contains the name of the
protocol that further qualifies the search criteria. For example, if the
<em>port_number</em> is 10, and the <em>protocol_name</em> is tcp, then the
call will return the server that uses the TCP protocol on port number 10. If
this parameter is set to NULL, then the first server is returned, regardless of
the protocol used.</dd>
</dl>
<br>
<h3>Authorities</h3>
<p>No authorization is required.</p>
<br>
<h3>Return Value</h3>
<p><em>getservbyport()</em> returns a pointer. Possible values are:</p>
<ul>
<li>NULL (unsuccessful)<br>
<br>
</li>
<li>p (successful), where p is a pointer to <strong>struct
servent</strong>.</li>
</ul>
<p>The structure <strong>struct servent</strong> is defined in
<strong>&lt;netdb.h&gt;</strong>.</p>
<pre>
struct servent {
char *s_name;
char **s_aliases;
int s_port;
char *s_proto
};
</pre>
<p><em>s_name</em> points to the character string that contains the name of the
service. <em>s_aliases</em> is a pointer to a NULL-terminated array of
alternate names for the service. <em>s_port</em> is the port number assigned to
the service. <em>s_proto</em> is the protocol being used by the service.</p>
<br>
<h3><a name="USAGE_NOTES">Usage Notes</a></h3>
<ol>
<li>The iSeries Navigator or the following CL commands can be
used to access the services database file:<br>
<br>
<ul>
<li>WRKSRVTBLE (Work with Service Table Entries)<br>
<br>
</li>
<li>ADDSRVTBLE (Add Service Table Entry)<br>
<br>
</li>
<li>RMVSRVTBLE (Remove Service Table Entry)</li>
</ul>
<br>
</li>
<li>The pointer returned by <em>getservbyport()</em> points to static storage
that is overwritten on subsequent calls to the <em>getservbyport()</em>,
<em>getservbyname()</em>, or <em>getservent()</em> functions.<br>
<br>
</li>
<li>When the service information is obtained from the service database file,
the file is opened and the service information is retrieved (if it exists) from
the file. The file is then closed only if a <em>setservent()</em> with a
nonzero parameter value was not previously done.<br>
<br>
</li>
<li>A coded character set identifier (CCSID) of 65535 for the job requests that
no database translation be performed. For translation to occur for the protocol
name specified by the <em>protocol_name</em> parameter, or for the service
names returned in the servent structure, the job CCSID must be something other
than 65535.<br>
<br>
</li>
<li>Do not use the <em>getservbyport()</em> function in a multithreaded
environment. See the multithread alternative <em>getservbyport_r()</em>
function.<br>
<br>
</li>
<li>When you develop in C-based languages and an application is compiled with the _XOPEN_SOURCE
macro defined to the value 520 or greater, the <em>getservbyport()</em> API is mapped to
<em>qso_getservbyport98()</em>.</li>
</ol>
<br>
<h3>Related Information</h3>
<ul>
<li><a href="_xopen_source.htm">_XOPEN_SOURCE</a>--Using _XOPEN_SOURCE for the UNIX 98
compatible interface<br>
<br>
</li>
<li><a href="gsrvnm.htm">getservbyname()</a>--Get Port Number for Service
Name<br>
<br>
</li>
<li><a href="gsrvnt.htm">getservent()</a>--Get Next Entry from Service
Database<br>
<br>
</li>
<li><a href="ssrvnt.htm">setservent()</a>--Open Service Database<br>
<br>
</li>
<li><a href="esrvnt.htm">endservent()</a>--Close Service Database</li>
</ul>
<br>
<hr>
API introduced: V4R2
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