160 lines
8.2 KiB
HTML
160 lines
8.2 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE html
|
|
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
|
<html lang="en-us" xml:lang="en-us">
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<meta name="security" content="public" />
|
|
<meta name="Robots" content="index,follow" />
|
|
<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
|
|
<meta name="DC.Type" content="reference" />
|
|
<meta name="DC.Title" content="Example: Use gethostbyaddr_r() for threadsafe network routines" />
|
|
<meta name="abstract" content="Here is an example of a program that uses gethostbyaddr_r()." />
|
|
<meta name="description" content="Here is an example of a program that uses gethostbyaddr_r()." />
|
|
<meta name="DC.Relation" scheme="URI" content="example.htm" />
|
|
<meta name="DC.Relation" scheme="URI" content="cthread.htm" />
|
|
<meta name="DC.Relation" scheme="URI" content="routines.htm" />
|
|
<meta name="DC.Relation" scheme="URI" content="../apis/tsghosta.htm" />
|
|
<meta name="copyright" content="(C) Copyright IBM Corporation 2001, 2006" />
|
|
<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2001, 2006" />
|
|
<meta name="DC.Format" content="XHTML" />
|
|
<meta name="DC.Identifier" content="xthread" />
|
|
<meta name="DC.Language" content="en-us" />
|
|
<!-- All rights reserved. Licensed Materials Property of IBM -->
|
|
<!-- US Government Users Restricted Rights -->
|
|
<!-- Use, duplication or disclosure restricted by -->
|
|
<!-- GSA ADP Schedule Contract with IBM Corp. -->
|
|
<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
|
|
<link rel="stylesheet" type="text/css" href="./ic.css" />
|
|
<title>Example: Use gethostbyaddr_r() for threadsafe network
|
|
routines</title>
|
|
</head>
|
|
<body id="xthread"><a name="xthread"><!-- --></a>
|
|
<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
|
|
<h1 class="topictitle1">Example: Use <span class="apiname">gethostbyaddr_r()</span> for threadsafe network
|
|
routines</h1>
|
|
<div><p>Here is an example of a program that uses <span class="apiname">gethostbyaddr_r()</span>.</p>
|
|
<div class="section"><p>All other routines with names that end in "_r" have similar semantics
|
|
and are also threadsafe. This example program takes an IP address in the dotted-decimal
|
|
notation and prints the host name.</p>
|
|
</div>
|
|
<div class="section"><div class="note"><span class="notetitle">Note:</span> By using the code examples, you agree to the terms of the <a href="codedisclaimer.htm">Code license and disclaimer information</a>.</div>
|
|
</div>
|
|
<div class="example"> <pre>/********************************************************/
|
|
/* Header files */
|
|
/********************************************************/
|
|
#include </netdb.h>
|
|
#include <sys/param.h>
|
|
#include <netinet/in.h>
|
|
#include <stdlib.h>
|
|
#include <stdio.h>
|
|
#include <arpa/inet.h>
|
|
#include <sys/socket.h>
|
|
#define HEX00 '\x00'
|
|
#define NUMPARMS 2
|
|
/********************************************************/
|
|
/* Pass one parameter that is the IP address in */
|
|
/* dotted decimal notation. The host name will be */
|
|
/* displayed if found; otherwise, a message states */
|
|
/* host not found. */
|
|
/********************************************************/
|
|
int main(int argc, char *argv[])
|
|
{
|
|
int rc;
|
|
struct in_addr internet_address;
|
|
struct hostent hst_ent;
|
|
struct hostent_data hst_ent_data;
|
|
char dotted_decimal_address [16];
|
|
char host_name[MAXHOSTNAMELEN];
|
|
|
|
/**********************************************************/
|
|
/* Verify correct number of arguments have been passed */
|
|
/**********************************************************/
|
|
if (argc != NUMPARMS)
|
|
{
|
|
printf("Wrong number of parms passed\n");
|
|
exit(-1);
|
|
}
|
|
/**********************************************************/
|
|
/* Obtain addressability to parameters passed */
|
|
/**********************************************************/
|
|
strcpy(dotted_decimal_address, argv[1]);
|
|
|
|
/**********************************************************/
|
|
/* Initialize the structure-field */
|
|
/* hostent_data.host_control_blk with hexadecimal zeros */
|
|
/* before its initial use. If you require compatibility */
|
|
/* with other platforms, then you must initialize the */
|
|
/* entire hostent_data structure with hexadecimal zeros. */
|
|
/**********************************************************/
|
|
/* Initialize to hex 00 hostent_data structure */
|
|
/**********************************************************/
|
|
memset(&hst_ent_data,HEX00,sizeof(struct hostent_data));
|
|
|
|
/**********************************************************/
|
|
/* Translate an IP address from dotted decimal */
|
|
/* notation to 32-bit IP address format. */
|
|
/**********************************************************/
|
|
internet_address.s_addr=inet_addr(dotted_decimal_address);
|
|
|
|
/**********************************************************/
|
|
/* Obtain host name */
|
|
/**********************************************************/
|
|
/**********************************************************/
|
|
/* NOTE: The gethostbyaddr_r() returns an integer. */
|
|
/* The following are possible values: */
|
|
/* -1 (unsuccessful call) */
|
|
/* 0 (successful call) */
|
|
/**********************************************************/
|
|
rc=gethostbyaddr_r((char *) &internet_address,
|
|
sizeof(struct in_addr), AF_INET,
|
|
&hst_ent, &hst_ent_data);
|
|
|
|
if (rc== -1)
|
|
{
|
|
printf("Host name not found\n");
|
|
exit(-1);
|
|
}
|
|
else
|
|
{
|
|
/*****************************************************/
|
|
/* Copy the host name to an output buffer */
|
|
/*****************************************************/
|
|
(void) memcpy((void *) host_name,
|
|
/****************************************************/
|
|
/* You must address all the results through the */
|
|
/* hostent structure hst_ent. */
|
|
/* NOTE: Hostent_data structure hst_ent_data is just */
|
|
/* a data repository that is used to support the */
|
|
/* hostent structure. Applications should consider */
|
|
/* hostent_data a storage area to put host level data */
|
|
/* that the application does not need to access. */
|
|
/****************************************************/
|
|
(void *) hst_ent.h_name,
|
|
MAXHOSTNAMELEN);
|
|
/*****************************************************/
|
|
/* Print the host name */
|
|
/*****************************************************/
|
|
printf("The host name is %s\n", host_name);
|
|
|
|
}
|
|
exit(0);
|
|
}</pre>
|
|
</div>
|
|
</div>
|
|
<div>
|
|
<div class="familylinks">
|
|
<div class="parentlink"><strong>Parent topic:</strong> <a href="example.htm" title="These examples provide many sample programs that illustrate the more advanced socket concepts. You can use these sample programs to create your own applications that complete a similar task.">Examples: Socket application designs</a></div>
|
|
</div>
|
|
<div class="relconcepts"><strong>Related concepts</strong><br />
|
|
<div><a href="cthread.htm" title="A function is considered threadsafe if you can start it simultaneously in multiple threads within the same process.">Thread safety</a></div>
|
|
</div>
|
|
<div class="relref"><strong>Related reference</strong><br />
|
|
<div><a href="routines.htm" title="Socket network functions allow application programs to obtain information from the host, protocol, service, and network files.">Socket network functions</a></div>
|
|
</div>
|
|
<div class="relinfo"><strong>Related information</strong><br />
|
|
<div><a href="../apis/tsghosta.htm">gethostbyaddr_r()</a></div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html> |