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このページは、Lazarusでのネットワークプログラムについてのチュートリアルを開始するページになるでしょう。 この記事に、リンクやセクション、ページ、あなたのWikiへのリンクを追加していってください。（訳注：最初にこの元記事を書いた人はネットワークプログラミングの専門でなく、独学で勉強したことを書いているそうです。）

このページには、一般的な情報があります。

その他のネットワークのチュートリアル

• セキュア・プログラミング

• Sockets - TCP/IP ソケットコンポーネント

• lNet - 軽量ネットワークコンポーネント

XML

The Extensible Markup Language is a W3C recommended language created to interchange information between different systems. It is a text based way to store information. Modern data interchange languages such as XHTML, as well as most WebServices technologies, are based on XML.

Currently there is a set of units that provides support for XML on Lazarus. These units are called "XMLRead", "XMLWrite" and "DOM" and they are part of the Free Component Library (FCL) from the Free Pascal Compiler. The FCL is already on the default search path for the compiler on Lazarus, so you only need to add the units to your uses clause in order to get XML support. The FCL is not documented currently (October / 2005), so this short tutorial aims at introducing XML access using those units.

The XML DOM (Document Object Model) is a set of standarized objects that provide a similar interface for the use of XML on different languages and systems. The standard only specifies the methods, properties and other interface parts of the object, leaving the implementation free for different languages. The FCL currently supports fully the DOM 1.0.

Basic Example

Let´s say you want to access a XML file called 'C:\Programas\teste.xml'. Here is the file content:

<?xml version="1.0" encoding="ISO-8859-1"?>
<images directory="mydir">
 <imageNode URL="graphic.jpg" title="">
   <Peca DestinoX="0" DestinoY="0">Pecacastelo.jpg1.swf</Peca>
   <Peca DestinoX="0" DestinoY="86">Pecacastelo.jpg2.swf</Peca>
 </imageNode>
</images>

The following code can write the Node´s names to a TMemo placed on a form:

var
 Documento: TXMLDocument;
 i, j: Integer;
begin
 Documento := TXMLDocument.Create;
 ReadXMLFile(Documento, 'C:\Programas\teste.xml');
 Memo.Lines.Clear;
 with Documento.DocumentElement.ChildNodes do
 begin
   for i := 0 to (Count - 1) do
   begin
     Memo.Lines.Add(Item[i].NodeName + ' ' + Item[i].NodeValue);
     for j := 0 to (Item[i].ChildNodes.Count - 1) do
     begin
       Memo.Lines.Add(Item[i].ChildNodes.Item[j].NodeName + ' '
        + Item[i].ChildNodes.Item[j].NodeValue);
     end;
   end;
 end;
 Documento.Free;
end;

Populating a TreeView with XML

One common use of XML files is to parse them and show their contents in a tree like format. You can find the TTreeView component on the "Common Controls" tab on Lazarus.

The function below will take a XML document previously loaded from a file or generated on code, and will populate a TreeView with it´s contents. The caption of each node will be the content of the first attribute of each node.

procedure TForm1.XML2Tree(tree: TTreeView; XMLDoc: TXMLDocument);
var
  iNode: TDOMNode;

  procedure ProcessNode(Node: TDOMNode; TreeNode: TTreeNode);
  var
    cNode: TDOMNode;
  begin
    if Node = nil then Exit; // Stops if reached a leaf
    
    // Adds a node to the tree
    TreeNode := tree.Items.AddChild(TreeNode, Node.Attributes[0].NodeValue);

    // Goes to the child node
    cNode := Node.ChildNodes.Item[0];

    // Processes all child nodes
    while cNode <> nil do
    begin
      ProcessNoDe(cNode, TreeNode);
      cNode := cNode.NextSibling;
    end;
  end;
    
begin
  iNode := XMLDoc.DocumentElement.ChildNodes.Item[0];
  while iNode <> nil do
  begin
    ProcessNode(iNode, nil); // Recursive
    iNode := iNode.NextSibling;
  end;
end;

Modifying a XML document

The first thing to remember is that TDOMDocument is the "handle" to the DOM. You can get an instance of this class by creating one or by loading a XML document.

Nodes on the other hand cannot be created like a normal object. You *must* use the methods provided by TDOMDocument to create them, and latter use other methods to put them on the correct place on the tree. This is because nodes must be "owned" by a specific document on DOM.

Below are some common methods from TDOMDocument:

   function CreateElement(const tagName: DOMString): TDOMElement; virtual;
   function CreateTextNode(const data: DOMString): TDOMText;
   function CreateCDATASection(const data: DOMString): TDOMCDATASection;
     virtual;
   function CreateAttribute(const name: DOMString): TDOMAttr; virtual;

And here an example method that will located the selected item on a TTreeView and then insert a child node to the XML document it represents. The TreeView must be previously filled with the contents of a XML file using the XML2Tree function.

procedure TForm1.actAddChildNode(Sender: TObject);
var
  Posicao: Integer;
  NovoNo: TDomNode;
begin
  {*******************************************************************
  *  Detects the selected element
  *******************************************************************}
  if TreeView1.Selected = nil then Exit;

  if TreeView1.Selected.Level = 0 then
  begin
    Posicao := TreeView1.Selected.Index;

    NovoNo := XMLDoc.CreateElement('item');
    TDOMElement(NovoNo).SetAttribute('nome', 'Item');
    TDOMElement(NovoNo).SetAttribute('arquivo', 'Arquivo');
    XMLDoc.DocumentElement.ChildNodes.Item[Posicao].AppendChild(NovoNo);

    {*******************************************************************
    *  Updates the TreeView
    *******************************************************************}
    TreeView1.Items.Clear;
    XML2Tree(TreeView1, XMLDoc);
  end
  else if TreeView1.Selected.Level >= 1 then
  begin
    {*******************************************************************
    *  This function only works on the first level of the tree,
    *  but can easely modifyed to work for any number of levels
    *******************************************************************}
  end;
end;

WebServices

According to the W3C a Web service is a software system designed to support interoperable machine-to-machine interaction over a network. It has an interface that is described in a machine-processable format such as WSDL. Other systems interact with the Web service in a manner prescribed by its interface using messages, which may be enclosed in a SOAP envelope, or follow a REST approach. These messages are typically conveyed using HTTP, and are normally comprised of XML in conjunction with other Web-related standards. Software applications written in various programming languages and running on various platforms can use web services to exchange data over computer networks like the Internet in a manner similar to inter-process communication on a single computer. This interoperability (e.g., between Windows and Linux applications) is due to the use of open standards. OASIS and the W3C are the primary committees responsible for the architecture and standardization of web services. To improve interoperability between web service implementations, the WS-I organisation has been developing a series of profiles to further define the standards involved.

Web Service Toolkit for FPC & Lazarus

Web Service Toolkit is a web services package for FPC and Lazarus.

External Links

XML

• W3Schools Xml Tutorial