107 lines
6.8 KiB
HTML
107 lines
6.8 KiB
HTML
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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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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Create a connectionless socket" />
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<meta name="abstract" content="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." />
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<meta name="description" content="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." />
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<meta name="DC.Relation" scheme="URI" content="../apis/close.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2001, 2006" />
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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>Create a connectionless socket</title>
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</head>
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<body id="connectionless"><a name="connectionless"><!-- --></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">Create a connectionless socket</h1>
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<div><p>Connectionless sockets do not establish a connection over which
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data is transferred. Instead, the server application specifies its name where
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a client can send requests.</p>
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<div class="section"><p>Connectionless sockets use User Datagram Protocol (UDP) instead
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of TCP/IP. </p>
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<p>The
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following figure illustrates the client/server relationship from the socket
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APIs used in the code examples for a connectionless socket design.</p>
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<br /><img src="rxab6503.gif" alt="The client/server relationship of the socket APIs for a connectionless protocol" /><br /></div>
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<div class="section"><h4 class="sectiontitle">Socket flow of events: Connectionless server</h4><p>The
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following sequence of the socket calls provide a description of the figure
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and the following example programs. It also describes the relationship
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between the server and client application in a connectionless design. Each
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set of flows contain links to usage notes on specific APIs. If you need more
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details on the use of a particular API, you can use these links. The first
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example uses the following sequence of function calls:</p>
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<ol><li>The <span class="apiname">socket()</span> function returns a socket descriptor representing
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an endpoint. The statement also identifies that the INET (Internet Protocol)
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address family with the UDP transport (SOCK_DGRAM) is used for this socket.</li>
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<li>After the socket descriptor is created, a <span class="apiname">bind()</span> function
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gets a unique name for the socket. In this example, the user sets the s_addr
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to zero, which means that the UDP port of 3555 is bound to all IPv4 addresses
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on the system.</li>
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<li>The server uses the <span class="apiname">recvfrom()</span> function to receive
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that data. The <span class="apiname">recvfrom()</span> function waits indefinitely for
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data to arrive.</li>
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<li>The <span class="apiname">sendto()</span> function echoes the data back to the client.</li>
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<li>The <span class="apiname">close()</span> function ends any open socket descriptors.</li>
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</ol>
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</div>
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<div class="section"><h4 class="sectiontitle">Socket flow of events: Connectionless client</h4><p>The
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second example uses the following sequence of function calls:</p>
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<ol><li>The <span class="apiname">socket()</span> function returns a socket descriptor representing
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an endpoint. The statement also identifies that the INET (Internet Protocol)
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address family with the UDP transport (SOCK_DGRAM) is used for this socket.
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</li>
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<li>In the client example program, if the server string that was passed into
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the inet_addr() function was not a dotted decimal IP address, then it is assumed
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to be the hostname of the server. In that case, use the <span class="apiname">gethostbyname()</span> function
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to retrieve the IP address of the server.</li>
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<li>Use the <span class="apiname">sendto()</span> function to send the data to the server. </li>
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<li>Use the <span class="apiname">recvfrom()</span> function to receive the data back
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from the server.</li>
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<li>The <span class="apiname">close()</span> function ends any open socket descriptors. </li>
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</ol>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="xconlessserver.htm">Example: A connectionless server</a></strong><br />
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This example can be used to create your own connectionless server design. This example uses User Datagram Protocol (UDP) to create a connectionless socket server program.</li>
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<li class="ulchildlink"><strong><a href="xconlessclient.htm">Example: A connectionless client</a></strong><br />
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This example shows how to use User Datagram Protocol (UDP) to connect a connectionless socket client program to a server.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="bdesign.htm" title="This topic provides examples of sockets programs that use the most basic design.">Basic socket design</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/close.htm">close()</a></div>
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<div><a href="../apis/socket.htm">socket()</a></div>
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<div><a href="../apis/bind.htm">bind()</a></div>
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<div><a href="../apis/recvfr.htm">recvfrom()</a></div>
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<div><a href="../apis/sendto.htm">sendto()</a></div>
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<div><a href="../apis/ghostnm.htm">gethostbyname()</a></div>
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</div>
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</div>
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</body>
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</html> |