186 lines
8.9 KiB
HTML
186 lines
8.9 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 name="Robots" content="index,follow" />
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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: A connectionless client" />
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<meta name="abstract" content="This example shows how to use User Datagram Protocol (UDP) to connect a connectionless socket client program to a server." />
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<meta name="description" content="This example shows how to use User Datagram Protocol (UDP) to connect a connectionless socket client program to a server." />
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<meta name="DC.Relation" scheme="URI" content="connectionless.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="xconlessclient" />
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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: A connectionless client</title>
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</head>
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<body id="xconlessclient"><a name="xconlessclient"><!-- --></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: A connectionless client</h1>
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<div><p>This example shows how to use User Datagram Protocol (UDP) to connect
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a connectionless socket client program to a server.</p>
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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
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of the <a href="codedisclaimer.htm">Code license and disclaimer information</a>.</div>
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</div>
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<div class="section"><pre>/**************************************************************************/
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/* This sample program provides a code for a connectionless client. */
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/**************************************************************************/
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/**************************************************************************/
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/* Header files needed for this sample program */
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/**************************************************************************/
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#include <stdio.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <netdb.h>
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/**************************************************************************/
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/* Constants used by this program */
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/**************************************************************************/
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#define SERVER_PORT 3555
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#define BUFFER_LENGTH 100
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#define FALSE 0
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#define SERVER_NAME "ServerHostName"
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/* Pass in 1 parameter which is either the */
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/* address or host name of the server, or */
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/* set the server name in the #define */
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/* SERVER_NAME */
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void main(int argc, char *argv[])
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{
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/***********************************************************************/
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/* Variable and structure definitions. */
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/***********************************************************************/
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int sd, rc;
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char server[NETDB_MAX_HOST_NAME_LENGTH];
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char buffer[BUFFER_LENGTH];
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struct hostent *hostp;
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struct sockaddr_in serveraddr;
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int serveraddrlen = sizeof(serveraddr);
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/***********************************************************************/
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/* A do/while(FALSE) loop is used to make error cleanup easier. The */
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/* close() of the socket descriptor is only done once at the very end */
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/* of the program. */
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/***********************************************************************/
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do
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{
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/********************************************************************/
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/* The socket() function returns a socket descriptor representing */
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/* an endpoint. The statement also identifies that the INET */
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/* (Internet Protocol) address family with the UDP transport */
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/* (SOCK_STREAM) will be used for this socket. */
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/********************************************************************/
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sd = socket(AF_INET, SOCK_DGRAM, 0);
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if (sd < 0)
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{
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perror("socket() failed");
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break;
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}
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/********************************************************************/
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/* If an argument was passed in, use this as the server, otherwise */
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/* use the #define that is located at the top of this program. */
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/********************************************************************/
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if (argc > 1)
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strcpy(server, argv[1]);
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else
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strcpy(server, SERVER_NAME);
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memset(&serveraddr, 0, sizeof(serveraddr));
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serveraddr.sin_family = AF_INET;
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serveraddr.sin_port = htons(SERVER_PORT);
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serveraddr.sin_addr.s_addr = inet_addr(server);
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if (serveraddr.sin_addr.s_addr == (unsigned long)INADDR_NONE)
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{
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/*****************************************************************/
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/* The server string that was passed into the inet_addr() */
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/* function was not a dotted decimal IP address. It must */
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/* therefore be the hostname of the server. Use the */
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/* gethostbyname() function to retrieve the IP address of the */
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/* server. */
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/*****************************************************************/
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hostp = gethostbyname(server);
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if (hostp == (struct hostent *)NULL)
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{
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printf("Host not found --> ");
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printf("h_errno = %d\n", h_errno);
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break;
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}
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memcpy(&serveraddr.sin_addr,
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hostp->h_addr,
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sizeof(serveraddr.sin_addr));
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}
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/********************************************************************/
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/* Initialize the data block that is going to be sent to the server */
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/********************************************************************/
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memset(buffer, 0, sizeof(buffer));
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strcpy(buffer, "A CLIENT REQUEST");
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/********************************************************************/
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/* Use the sendto() function to send the data to the server. */
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/********************************************************************/
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rc = sendto(sd, buffer, sizeof(buffer), 0,
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(struct sockaddr *)&serveraddr,
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sizeof(serveraddr));
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if (rc < 0)
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{
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perror("sendto() failed");
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break;
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}
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/********************************************************************/
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/* Use the recvfrom() function to receive the data back from the */
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/* server. */
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/********************************************************************/
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rc = recvfrom(sd, buffer, sizeof(buffer), 0,
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(struct sockaddr *)&serveraddr,
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& serveraddrlen);
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if (rc < 0)
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{
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perror("recvfrom() failed");
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break;
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}
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printf("client received the following: <%s>\n", buffer);
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printf("from port %d, from address %s\n",
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ntohs(serveraddr.sin_port),
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inet_ntoa(serveraddr.sin_addr));
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/********************************************************************/
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/* Program complete */
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/********************************************************************/
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} while (FALSE);
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/***********************************************************************/
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/* Close down any open socket descriptors */
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/***********************************************************************/
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if (sd != -1)
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close(sd);
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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="connectionless.htm" title="Connectionless sockets do not establish a connection over which data is transferred. Instead, the server application specifies its name where a client can send requests.">Create a connectionless socket</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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