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