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This page will be the start for tutorials with regard to network programming with Lazarus. I am not an expert on networking programming and I will add to the article as I learn about it. I invite others to help create networking articles. Just add a link to the next section, add a page and create your own WiKi article. On this page some general information will be given.

Template:Web and Networking Programming

TCP/IP Protocol

SSH/Telnet client example

See the Synapse page.

Webserver example

Given below is an example http server written with Synapse and tested in Mac OS X, after changing the synapse source to use a fixed constant $20000 as MSG_NOSIGNAL, because this constant isn't present in the sockets unit in Mac OS X.

  The Micro Pascal WebServer

  This is a very simple example webserver implemented with the Synapse library.

  It works with blocking sockets and a single thread, so it
  can only handle one request at a given time.

  It will write the headers that it receives from the browser
  to the standard output.

  It serves a fixed webpage for the / URI
  For any other URI it will return 404 not found
program upserver;

{$ifdef fpc}
  {$mode delphi}

{$apptype console}

  Classes, blcksock, sockets, Synautil, SysUtils;

  Attends a connection. Reads the headers and gives an
  appropriate response
procedure AttendConnection(ASocket: TTCPBlockSocket);
  timeout: integer;
  s: string;
  method, uri, protocol: string;
  OutputDataString: string;
  ResultCode: integer;
  timeout := 120000;

  WriteLn('Received headers+document from browser:');

  //read request line
  s := ASocket.RecvString(timeout);
  method := fetch(s, ' ');
  uri := fetch(s, ' ');
  protocol := fetch(s, ' ');

  //read request headers
    s := ASocket.RecvString(Timeout);
  until s = '';

  // Now write the document to the output stream

  if uri = '/' then
    // Write the output document to the stream
    OutputDataString :=
      '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"'
      + ' "">' + CRLF
      + '<html><h1>Teste</h1></html>' + CRLF;

    // Write the headers back to the client
    ASocket.SendString('HTTP/1.0 200' + CRLF);
    ASocket.SendString('Content-type: Text/Html' + CRLF);
    ASocket.SendString('Content-length: ' + IntTostr(Length(OutputDataString)) + CRLF);
    ASocket.SendString('Connection: close' + CRLF);
    ASocket.SendString('Date: ' + Rfc822DateTime(now) + CRLF);
    ASocket.SendString('Server: Servidor do Felipe usando Synapse' + CRLF);
    ASocket.SendString('' + CRLF);

  //  if ASocket.lasterror <> 0 then HandleError;

    // Write the document back to the browser
    ASocket.SendString('HTTP/1.0 404' + CRLF);

  ListenerSocket, ConnectionSocket: TTCPBlockSocket;
  ListenerSocket := TTCPBlockSocket.Create;
  ConnectionSocket := TTCPBlockSocket.Create;


    if ListenerSocket.canread(1000) then
      ConnectionSocket.Socket := ListenerSocket.accept;
      WriteLn('Attending Connection. Error code (0=Success): ', ConnectionSocket.lasterror);
  until false;



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.

See also