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467 lines
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467 lines
26 KiB
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/network.doc:41 -->
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Network Module</title>
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<table border="0" cellpadding="0" cellspacing="0" width="100%">
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<a href="index.html">
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<font color="#004faf">Home</font></a>
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<font color="#004faf">All Classes</font></a>
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<font color="#004faf">Main Classes</font></a>
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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Network Module</h1>
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<p>
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<p> <!-- toc -->
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<ul>
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<li><a href="#1"> Introduction
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</a>
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<li><a href="#2"> Working Network Protocol independently with TQUrlOperator and TQNetworkOperation
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</a>
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<ul>
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<li><a href="#2-1"> Implementing your own Network Protocol
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</a>
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<li><a href="#2-2"> Error Handling
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</a>
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</ul>
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</ul>
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<!-- endtoc -->
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<p> <h2> Introduction
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</h2>
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<a name="1"></a><p> The network module offers classes to make network programming easier
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and portable. Essentially, there are three sets of classes, first low
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level classes like <a href="ntqsocket.html">TQSocket</a>, <a href="ntqserversocket.html">TQServerSocket</a>, <a href="ntqdns.html">TQDns</a>, etc. which
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allow you to work in a portable way with TCP/IP sockets. In addition,
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there are classes like <a href="ntqnetworkprotocol.html">TQNetworkProtocol</a>, <a href="qnetworkoperation.html">TQNetworkOperation</a> in
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the TQt base library, which provide an abstract layer for implementing
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network protocols and <a href="ntqurloperator.html">TQUrlOperator</a> which operates on such network
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protocols. Finally the third set of network classes are the passive
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ones, specifically <a href="ntqurl.html">TQUrl</a> and <a href="ntqurlinfo.html">TQUrlInfo</a> which do URL parsing and
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similar.
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<p> The first set of classes (<a href="ntqsocket.html">TQSocket</a>, <a href="ntqserversocket.html">TQServerSocket</a>, <a href="ntqdns.html">TQDns</a>, <a href="ntqftp.html">TQFtp</a>, etc.) are included in TQt's "network" module.
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<p> The <a href="ntqsocket.html">TQSocket</a> classes are not directly related to the TQNetwork classes,
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but TQSocket should and will be used for implementing network
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protocols, which are directly related to the TQNetwork classes. For
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example, the <a href="ntqftp.html">TQFtp</a> class (which implements the FTP protocol) uses
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TQSockets. But TQSockets don't need to be used for protocol
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implementations, e.g. <a href="ntqlocalfs.html">TQLocalFs</a> (which is an implementation of the
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local filesystem as network protocol) uses <a href="ntqdir.html">TQDir</a> and doesn't use
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TQSocket. Using TQNetworkProtocols you can implement everything which
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fits into a hierarchical structure and can be accessed using URLs.
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This could be, for example, a protocol which can read pictures from a
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digital camera using a serial connection.
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<p> <h2> Working Network Protocol independently with <a href="ntqurloperator.html">TQUrlOperator</a> and <a href="qnetworkoperation.html">TQNetworkOperation</a>
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</h2>
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<a name="2"></a><p> It is quite easy to just use existing network protocol implementations
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and operate on URLs. For example, downloading a file from an FTP
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server to the local filesystem can be done with following code:
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<p> <pre>
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<a href="ntqurloperator.html">TQUrlOperator</a> op;
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op.<a href="ntqurloperator.html#copy">copy</a>( "ftp://ftp.trolltech.com/qt/source/qt-2.1.0.tar.gz", "file:/tmp", FALSE );
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</pre>
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<p> And that's all! Of course an implementation of the FTP protocol has to
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be available and registered for doing that. More information on that
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later.
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<p> You can also do things like creating directories, removing files,
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renaming, etc. For example, to create a folder on a private FTP
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account do
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<p> <pre>
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<a href="ntqurloperator.html">TQUrlOperator</a> op( "ftp://username:password@host.domain.no/home/username" );
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op.<a href="ntqurloperator.html#mkdir">mkdir</a>( "New Directory" );
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</pre>
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<p> To see all available operations, look at the <a href="ntqurloperator.html">TQUrlOperator</a> class
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documentation.
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<p> Since networking works asynchronously, the function call for an
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operation will normally return before the operation has been
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completed. This means that the function cannot return a value
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indicating failure or success. Instead, the return value always is a
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pointer to a <a href="qnetworkoperation.html">TQNetworkOperation</a>, and this object stores
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all the information about the operation.
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<p> For example, <a href="qnetworkoperation.html">TQNetworkOperation</a> has a method which returns the state
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of this operation. Using this you can find out the state of the
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operation at any time. The object also makes available the arguments
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you passed to the <a href="ntqurloperator.html">TQUrlOperator</a> method, the type of the operation
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and some more information. For more details see the class
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documentation of <a href="qnetworkoperation.html">TQNetworkOperation</a>.
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<p> The <a href="ntqurloperator.html">TQUrlOperator</a> emits signals to inform you about the progress of
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the operations. As you can call many methods which operate on a <a href="ntqurloperator.html">TQUrlOperator</a>'s URL, it queues up all the operations. So you can't know
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which operation the <a href="ntqurloperator.html">TQUrlOperator</a> just processed. Clearly you will
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want to know which operation just took place, so each signal's last
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argument is a pointer to the <a href="qnetworkoperation.html">TQNetworkOperation</a> object which was
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just processed and which caused the signal to be emitted.
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<p> Some of these operations send a <tt>start()</tt> signal at the beginning (if
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this makes sense), and some of them send some signals during
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processing. All operations send a <tt>finished()</tt> signal after they are
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done. To find that out if an operation finished successfully you can
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use the <a href="qnetworkoperation.html">TQNetworkOperation</a> pointer you got with the <tt>finished()</tt>
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signal. If <a href="qnetworkoperation.html#state">TQNetworkOperation::state</a>() equals <a href="ntqnetworkprotocol.html#State-enum">TQNetworkProtocol::StDone</a> the operation finished successfully, if it is
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<a href="ntqnetworkprotocol.html#State-enum">TQNetworkProtocol::StFailed</a> the operation failed.
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<p> Example: A slot which you might connect to the
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<tt>TQUrlOperator::finished( TQNetworkOperation * )</tt>
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<pre>
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void MyClass::slotOperationFinished( <a href="qnetworkoperation.html">TQNetworkOperation</a> *op )
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{
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switch ( op-><a href="qnetworkoperation.html#operation">operation</a>() ) {
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case TQNetworkProtocol::OpMkDir:
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if ( op-><a href="qnetworkoperation.html#state">state</a>() == TQNetworkProtocol::StFailed )
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<a href="ntqapplication.html#qDebug">tqDebug</a>( "Couldn't create directory %s", op-><a href="qnetworkoperation.html#arg">arg</a>( 0 ).latin1() );
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else
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<a href="ntqapplication.html#qDebug">tqDebug</a>( "Successfully created directory %s", op-><a href="qnetworkoperation.html#arg">arg</a>( 0 ).latin1() );
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break;
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// ... and so on
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}
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}
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</pre>
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<p> As mentioned earlier, some operations send other signals too. Let's
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take the list children operation as an example (e.g. read a directory
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on a FTP server):
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<p> <pre>
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TQUrlOperator op;
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MyClass::MyClass() : <a href="ntqobject.html">TQObject</a>(), op( "ftp://ftp.trolltech.com" )
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{
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connect( &op, TQ_SIGNAL( newChildren( const <a href="ntqvaluelist.html">TQValueList</a><TQUrlInfo> &, TQNetworkOperation * ) ),
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this, TQ_SLOT( slotInsertEntries( const <a href="ntqvaluelist.html">TQValueList</a><TQUrlInfo> &, TQNetworkOperation * ) ) );
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connect( &op, TQ_SIGNAL( start( <a href="qnetworkoperation.html">TQNetworkOperation</a> * ) ),
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this, TQ_SLOT( slotStart( <a href="qnetworkoperation.html">TQNetworkOperation</a> *) ) );
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connect( &op, TQ_SIGNAL( finished( <a href="qnetworkoperation.html">TQNetworkOperation</a> * ) ),
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this, TQ_SLOT( slotFinished( <a href="qnetworkoperation.html">TQNetworkOperation</a> *) ) );
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}
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void MyClass::slotInsertEntries( const <a href="ntqvaluelist.html">TQValueList</a><TQUrlInfo> &info, TQNetworkOperation * )
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{
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TQValueList<TQUrlInfo>::ConstIterator it = info.<a href="ntqvaluelist.html#begin">begin</a>();
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for ( ; it != info.<a href="ntqvaluelist.html#end">end</a>(); ++it ) {
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const <a href="ntqurlinfo.html">TQUrlInfo</a> &inf = *it;
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<a href="ntqapplication.html#qDebug">tqDebug</a>( "Name: %s, Size: %d, Last Modified: %s",
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inf.<a href="ntqurlinfo.html#name">name</a>().latin1(), inf.<a href="ntqurlinfo.html#size">size</a>(), inf.<a href="ntqurlinfo.html#lastModified">lastModified</a>().toString().latin1() );
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}
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}
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void MyClass::slotStart( <a href="qnetworkoperation.html">TQNetworkOperation</a> * )
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{
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<a href="ntqapplication.html#qDebug">tqDebug</a>( "Start reading '%s'", op.toString().latin1() );
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}
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void MyClass::slotFinished( <a href="qnetworkoperation.html">TQNetworkOperation</a> *operation )
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{
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if ( operation-><a href="qnetworkoperation.html#operation">operation</a>() == TQNetworkProtocol::OpListChildren ) {
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if ( operation-><a href="qnetworkoperation.html#state">state</a>() == TQNetworkProtocol::StFailed )
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<a href="ntqapplication.html#qDebug">tqDebug</a>( "Couldn't read '%s'! Following error occurred: %s",
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op.toString().latin1(), operation-><a href="qnetworkoperation.html#protocolDetail">protocolDetail</a>().latin1() );
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else
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<a href="ntqapplication.html#qDebug">tqDebug</a>( "Finished reading '%s'!", op.toString().latin1() );
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}
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}
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</pre>
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<p> These examples demonstrate now how to use the <a href="ntqurloperator.html">TQUrlOperator</a> and <tt>TQNetworkOperations</tt>. The network extension also contains useful example
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code.
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<p> <h3> Implementing your own Network Protocol
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</h3>
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<a name="2-1"></a><p> <a href="ntqnetworkprotocol.html">TQNetworkProtocol</a> provides a base class for implementations
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of network protocols and an architecture for the a dynamic
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registration and de-registration of network protocols. If you use this
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architecture you don't need to care about asynchronous programming, as
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the architecture hides this and does all the work for you.
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<p> <em>Note</em> It is difficult to design a base class for network protocols
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which is useful for all network protocols. The architecture described
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here is designed to work with all kinds of hierarchical structures,
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like filesystems. So everything which can be interpreted as
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hierarchical structure and accessed via URLs, can be implemented as
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network protocol and easily used in TQt. This is not limited to
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filesystems only!
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<p> To implement a network protocol create a class derived from
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<a href="ntqnetworkprotocol.html">TQNetworkProtocol</a>.
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<p> Other classes will use this network protocol implementation
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to operate on it. So you should reimplement following protected members
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<p> <pre>
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void TQNetworkProtocol::operationListChildren( <a href="qnetworkoperation.html">TQNetworkOperation</a> *op );
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void TQNetworkProtocol::operationMkDir( <a href="qnetworkoperation.html">TQNetworkOperation</a> *op );
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void TQNetworkProtocol::operationRemove( <a href="qnetworkoperation.html">TQNetworkOperation</a> *op );
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void TQNetworkProtocol::operationRename( <a href="qnetworkoperation.html">TQNetworkOperation</a> *op );
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void TQNetworkProtocol::operationGet( <a href="qnetworkoperation.html">TQNetworkOperation</a> *op );
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void TQNetworkProtocol::operationPut( <a href="qnetworkoperation.html">TQNetworkOperation</a> *op );
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</pre>
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<p> Some notes on reimplementing these methods: You always get a pointer
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to a <a href="qnetworkoperation.html">TQNetworkOperation</a> as argument. This pointer holds all the
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information about the operation in the current state. If you start
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processing such an operation, set the state to <a href="ntqnetworkprotocol.html#State-enum">TQNetworkProtocol::StInProgress</a>. If you finished processing the
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operation, set the state to <a href="ntqnetworkprotocol.html#State-enum">TQNetworkProtocol::StDone</a> if it was
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successful or <a href="ntqnetworkprotocol.html#State-enum">TQNetworkProtocol::StFailed</a> if an error occurred. If
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an error occurred you must set an error code (see
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<a href="qnetworkoperation.html#setErrorCode">TQNetworkOperation::setErrorCode</a>()) and if you know some details
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(e.g. an error message) you can also set this message to the operation
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pointer (see <a href="qnetworkoperation.html#setProtocolDetail">TQNetworkOperation::setProtocolDetail</a>()). Also you get
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all the relevant information (type, arguments, etc.) about the
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operation from the <a href="qnetworkoperation.html">TQNetworkOperation</a> pointer. For details about
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which arguments you can get and set look at <a href="qnetworkoperation.html">TQNetworkOperation</a>'s
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class documentation.
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<p> If you reimplement an operation function, it's very important to emit
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the correct signals at the correct time: In general always emit <tt>finished()</tt> at the end of an operation (when you either successfully
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finished processing the operation or an error occurred) with the
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network operation as argument. The whole network architecture relies
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on correctly emitted <tt>finished()</tt> signals! Then there are some more
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specialized signals which are specific to operations:
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<ul>
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<li> Emit in <tt>operationListChildren</tt>:
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<ul>
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<li> <tt>start()</tt> just before starting to list the children
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<li> <tt>newChildren()</tt> when new children are read
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</ul>
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<li> Emit in <tt>operationMkDir</tt>:
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<ul>
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<li> <tt>createdDirectory()</tt> after the directory has been created
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<li> <tt>newChild()</tt> (or newChildren()) after the directory has been
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created (since a new directory is a new child)
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</ul>
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<li> Emit in <tt>operationRemove</tt>:
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<ul>
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<li> <tt>removed()</tt> after a child has been removed
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</ul>
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<li> Emit in <tt>operationRename</tt>:
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<ul>
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<li> <tt>itemChanged()</tt> after a child has been renamed
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</ul>
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<li> Emit in <tt>operationGet</tt>:
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<ul>
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<li> <tt>data()</tt> each time new data has been read
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<li> <tt>dataTransferProgress()</tt> each time new data has been read to
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indicate how much of the data has been read now.
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</ul>
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<li> Emit in <tt>operationPut</tt>:
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<ul>
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<li> <tt>dataTransferProgress()</tt> each time data has been written to
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indicate how much of the data has been written. Although you
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know the whole data when this operation is called, it's
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suggested not to write the whole data at once, but to do it
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step by step to avoid blocking the GUI. Doing things
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incrementally also means that progress can be made visible
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to the user.
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</ul>
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</ul>
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<p> And remember, always emit the <tt>finished()</tt> signal at the end!
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<p> For more details about these signals' arguments look at the <a href="ntqnetworkprotocol.html">TQNetworkProtocol</a> class documentation.
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<p> Here is a list of which <a href="qnetworkoperation.html">TQNetworkOperation</a> arguments you can get and
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which you must set in which function:
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<p> (To get the URL on which you should work, use the <a href="ntqnetworkprotocol.html#url">TQNetworkProtocol::url</a>() method which returns a pointer to the URL
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operator. Using that you can get the path, host, name filter, etc.)
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<p> <ul>
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<li> In <tt>operationListChildren</tt>:
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<ul>
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<li> Nothing.
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</ul>
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<li> In <tt>operationMkDir</tt>:
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<ul>
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<li> <tt>TQNetworkOperation::arg( 0 )</tt> contains the name of the directory which should be created
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</ul>
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<li> In <tt>operationRemove</tt>:
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<ul>
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<li> <tt>TQNetworkOperation::arg( 0 )</tt> contains the name of the file
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which should be removed. Normally this is a relative name. But
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it could be absolute. Use <a href="ntqurl.html">TQUrl</a>( op->arg( 0 ) ).fileName()
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to get the filename.
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</ul>
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<li> In <tt>operationRename</tt>:
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<ul>
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<li> <tt>TQNetworkOperation::arg( 0 )</tt> contains the name of the file
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which should be renamed
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<li> <tt>TQNetworkOperation::arg( 1 )</tt> contains the name to which it
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should be renamed.
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</ul>
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<li> In <tt>operationGet</tt>:
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<ul>
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<li> <tt>TQNetworkOperation::arg( 0 )</tt> contains the full URL of the
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file which should be retrieved.
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</ul>
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<li> In <tt>operationPut</tt>:
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<ul>
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<li> <tt>TQNetworkOperation::arg( 0 )</tt> contains the full URL of the
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file in which the data should be stored.
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<li> <tt>TQNetworkOperation::rawArg( 1 )</tt> contains the data which
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should be stored in <tt>TQNetworkOperation::arg( 0 )</tt>
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</ul>
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</ul>
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<p> In summary: If you reimplement an operation function, you must emit
|
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some special signals and at the end you must <em>always</em> emit a <tt>finished()</tt> signal, regardless of success or failure. Also you must
|
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change the state of the <a href="qnetworkoperation.html">TQNetworkOperation</a> during processing. You
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can also get and set <a href="qnetworkoperation.html">TQNetworkOperation</a> arguments as the operation
|
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progresses.
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<p> It may occur that the network protocol you implement only requires a
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subset of these operations. In such cases, simply reimplement the
|
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operations which are supported by the protocol. Additionally you must
|
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specify which operations you support. This is achieved by
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reimplementing
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<p> <pre>
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int TQNetworkProtocol::supportedOperations() const;
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</pre>
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|
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<p> In your implementation of this method return an <tt>int</tt> value
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which is constructed by OR-ing together the correct values
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(supported operations) of the following enum (of <a href="ntqnetworkprotocol.html">TQNetworkProtocol</a>):
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<p> <ul>
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<li> <tt>OpListChildren</tt>
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<li> <tt>OpMkDir</tt>
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<li> <tt>OpRemove</tt>
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<li> <tt>OpRename</tt>
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<li> <tt>OpGet</tt>
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<li> <tt>OpPut</tt>
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</ul>
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<p> For example, if your protocol supports listing children and renaming
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them, your implementation of <tt>supportedOperations()</tt> should do this:
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<p> <pre>
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return OpListChildren | OpRename;
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</pre>
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<p> The last method you must reimplement is
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<p> <pre>
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bool TQNetworkProtocol::checkConnection( <a href="qnetworkoperation.html">TQNetworkOperation</a> *op );
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</pre>
|
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<p> Here you must return TRUE, if the connection is up and okay (this means
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operations on the protocol can be done). If the connection is not okay,
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return FALSE and start to try opening it. If you cannot open the
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connection at all (e.g. because the host is not found), emit a <tt>finished()</tt>
|
|
signal and set an error code and the <a href="ntqnetworkprotocol.html#State-enum">TQNetworkProtocol::StFailed</a> state to
|
|
the <a href="qnetworkoperation.html">TQNetworkOperation</a> pointer you get here.
|
|
<p> Now, you never need to check before doing an operation yourself, if
|
|
the connection is okay. The network architecture does this, which
|
|
means it uses <tt>checkConnection()</tt> to see if an operation can be done
|
|
and if not, it tries it again and again for some time, only calling an
|
|
operation function if the connection is okay.
|
|
<p> To be able to use a network protocol with a <a href="ntqurloperator.html">TQUrlOperator</a> (and so, for
|
|
example, in the <a href="ntqfiledialog.html">TQFileDialog</a>), you must register the network
|
|
protocol implementation. This can be done like this:
|
|
<p> <pre>
|
|
TQNetworkProtocol::<a href="ntqnetworkprotocol.html#registerNetworkProtocol">registerNetworkProtocol</a>( "myprot", new TQNetworkProtocolFactory<MyProtocol> );
|
|
</pre>
|
|
|
|
<p> In this case <tt>MyProtocol</tt> would be a class you implemented as
|
|
described here (derived from <a href="ntqnetworkprotocol.html">TQNetworkProtocol</a>) and the name of the
|
|
protocol would be "myprot". So to use it, you would do something like
|
|
<p> <pre>
|
|
<a href="ntqurloperator.html">TQUrlOperator</a> op( "myprot://host/path" );
|
|
op.<a href="ntqurloperator.html#listChildren">listChildren</a>();
|
|
</pre>
|
|
|
|
<p> Finally, as example of a network protocol implementation you could
|
|
look at the implementation of <a href="ntqlocalfs.html">TQLocalFs</a>. The network extension also
|
|
contains an example implementation of a network protocol.
|
|
<p> <h3> Error Handling
|
|
</h3>
|
|
<a name="2-2"></a><p> Error handling is important for both implementing new network
|
|
protocols for and using them (through <a href="ntqurloperator.html">TQUrlOperator</a>).
|
|
<p> After processing an operation has been finished the network operation
|
|
the <a href="ntqurloperator.html">TQUrlOperator</a> emits the <tt>finished()</tt> signal. This has as argument
|
|
a pointer to the processed <a href="qnetworkoperation.html">TQNetworkOperation</a>. If the state of this
|
|
operation is <a href="ntqnetworkprotocol.html#State-enum">TQNetworkProtocol::StFailed</a>, the operation contains
|
|
some more information about this error. The following error codes are
|
|
defined in <a href="ntqnetworkprotocol.html">TQNetworkProtocol</a>:
|
|
<p> <center><table cellpadding="4" cellspacing="2" border="0">
|
|
<tr bgcolor="#a2c511"> <th valign="top">Error <th valign="top">Meaning
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::NoError</a>
|
|
<td valign="top">No error occurred
|
|
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrValid</a>
|
|
<td valign="top">The URL you are operating on is not valid
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrUnknownProtocol</a>
|
|
<td valign="top">There is no protocol implementation available for the protocol
|
|
of the URL you are operating on (e.g. if the protocol is http
|
|
and no http implementation has been registered)
|
|
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrUnsupported</a>
|
|
<td valign="top">The operation is not supported by the protocol
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrParse</a>
|
|
<td valign="top">Parse error of the URL
|
|
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrLoginIncorrect</a>
|
|
<td valign="top">You needed to login but the username or password are wrong
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrHostNotFound</a>
|
|
<td valign="top">The specified host (in the URL) couldn't be found
|
|
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrListChildren</a>
|
|
<td valign="top">An error occurred while listing the children
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrMkDir</a>
|
|
<td valign="top">An error occurred when creating a directory
|
|
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrRemove</a>
|
|
<td valign="top">An error occurred while removing a child
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrRename</a>
|
|
<td valign="top">An error occurred while renaming a child
|
|
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrGet</a>
|
|
<td valign="top">An error occurred while getting (retrieving) data
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrPut</a>
|
|
<td valign="top">An error occurred while putting (uploading) data
|
|
<tr bgcolor="#d0d0d0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrFileNotExisting</a>
|
|
<td valign="top">A file which is needed by the operation doesn't exist
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><a href="ntqnetworkprotocol.html#Error-enum">TQNetworkProtocol::ErrPermissionDenied</a>
|
|
<td valign="top">The permission for doing the operation has been denied
|
|
</table></center>
|
|
<p> <a href="qnetworkoperation.html#errorCode">TQNetworkOperation::errorCode</a>() returns one of these codes or
|
|
perhaps a different one if you use your an own network protocol
|
|
implementation which defines additional error codes.
|
|
<p> <tt>TQNetworkOperation::protocolDetails()</tt> may also return a string which
|
|
contains an error message then which might be suitable for display to
|
|
the user.
|
|
<p> If you implement your own network protocol, you must report any
|
|
errors which occurred. First you always need to be able to
|
|
access the <a href="qnetworkoperation.html">TQNetworkOperation</a> which is being processed at the
|
|
moment. This is done using <tt>TQNetworkOperation::operationInProgress()</tt>, which returns a pointer to
|
|
the current network operation or 0 if no operation is processed at the
|
|
moment.
|
|
<p> Now if an error occurred and you need to handle it, do this:
|
|
<pre>
|
|
if ( operationInProgress() ) {
|
|
operationInProgress()->setErrorCode( error_code_of_your_error );
|
|
operationInProgress()->setProtocolDetails( detail ); // optional
|
|
emit finished( operationInProgress() );
|
|
return;
|
|
}
|
|
</pre>
|
|
|
|
<p> That's all. The connection to the <a href="ntqurloperator.html">TQUrlOperator</a> and so on is done
|
|
automatically. Additionally, if the error was really bad so that no
|
|
more operations can be done in the current state (e.g. if the host
|
|
couldn't be found), call <tt>TQNetworkProtocol::clearOperationStack()</tt> <em>before</em> emitting <tt>finished()</tt>.
|
|
<p> Ideally you should use one of the predefined error codes of <a href="ntqnetworkprotocol.html">TQNetworkProtocol</a>. If this is not possible, you can add own error codes
|
|
- they are just normal <tt>int</tt>s. Just be careful that the value of the
|
|
error code doesn't conflict with an existing one.
|
|
<p> An example to look at is in qt/examples/network/ftpclient.
|
|
This is the implementation of a fairly complete FTP client, which
|
|
supports uploading and downloading files, making directories, etc.,
|
|
all done using <tt>TQUrlOperators</tt>.
|
|
<p> You might also like to look at <a href="ntqftp.html">TQFtp</a> (in qt/src/network/qftp.cpp) or at
|
|
the example in qt/examples/network/networkprotocol/nntp.cpp.
|
|
<p>
|
|
<!-- eof -->
|
|
<p><address><hr><div align=center>
|
|
<table width=100% cellspacing=0 border=0><tr>
|
|
<td>Copyright © 2007
|
|
<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
|
|
<td align=right><div align=right>TQt 3.3.8</div>
|
|
</table></div></address></body>
|
|
</html>
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