{*_* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Author:       Fran鏾is PIETTE
Description:  TWSocket class encapsulate the Windows Socket paradigm
Creation:     April 1996
Version:      5.18
EMail:        francois.piette@overbyte.be  http://www.overbyte.be
              francois.piette@rtfm.be      http://www.rtfm.be/fpiette
Support:      Use the mailing list twsocket@elists.org
              Follow "support" link at http://www.overbyte.be for subscription.
Legal issues: Copyright (C) 1996-2005 by Fran鏾is PIETTE
              Rue de Grady 24, 4053 Embourg, Belgium. Fax: +32-4-365.74.56
              <francois.piette@overbyte.be>

              This software is provided 'as-is', without any express or
              implied warranty.  In no event will the author be held liable
              for any  damages arising from the use of this software.

              Permission is granted to anyone to use this software for any
              purpose, including commercial applications, and to alter it
              and redistribute it freely, subject to the following
              restrictions:

              1. The origin of this software must not be misrepresented,
                 you must not claim that you wrote the original software.
                 If you use this software in a product, an acknowledgment
                 in the product documentation would be appreciated but is
                 not required.

              2. Altered source versions must be plainly marked as such, and
                 must not be misrepresented as being the original software.

              3. This notice may not be removed or altered from any source
                 distribution.

              4. You must register this software by sending a picture postcard
                 to the author. Use a nice stamp and mention your name, street
                 address, EMail address and any comment you like to say.

History:
Jul 18, 1996  Move all low level socket to winsock to be Delphi 2.x compatible
Sep 18, 1996  Use structured exception for handling errors
Sep 19, 1996  Check csDestroying before invoking event handler
Nov 04, 1996  Better error handling
Jan 31, 1997  Changed property assignation for Addr, Port and Proto
              Added notification handler
Feb 14, 1997  Corrected bug in property assignation for Addr, Port and Proto
Mar 26, 1997  Make UDP protocol work correctly
              Enable UDP broadcasting by using addr 255.255.255.255
Apr 1, 1997   Added class function when independent of any open socket
              Moved InitData as global
              Added ReceivedFrom function
              Added ResolveHost function
Jul 22, 1997  Adapted to Delphi 3 which has a modified winsock.accept
Aug 13, 1997  'sin' member made public
Aug 24, 1997  Create the only help
              Makes writing HSocket the same as calling Dup.
Sep 5, 1997   Version 2.01, added WinsockInfo function
Sep 21, 1997  Version 2.02, make it really thread safe
                            created global WSocketVersion
Sep 25, 1997  Version 2.04, port to C++Builder
Sep 27, 1997  Version 2.05. All class methods converted to global
              procedure or function because C++Builder do not like
              class method very much.
              Old class method              New global function
              ----------------              -------------------
              WinsockInfo                   WinsockInfo
              SocketErrorDesc               WSocketErrorDesc
              GetHostByAddr                 WSocketGetHostByAddr
              GetHostByName                 WSocketGetHostByName
              ResolveHost                   WSocketResolveHost
              HostName                      LocalHostName
Oct 02, 1997  V2.06 Added a check in destructor to avoid calling WSACleanup at
              design time which crashes the excellent Eagle Software CDK.
Oct 16, 1997  V2.07 Added PortNum property with numeric value for Port.
              Added RcvdCount property to return the number of
              characters received in the buffer but not read yet. Do not
              confuse with ReadCount which returns the number of chars
              already received.
              Added a check for FWait assignation in front of ReadLine
              Prefixed each TSocketState value by 'ws' to avoid name conflict.
              Moved FHSocket member to private section because the property
              HSocket does the right job.
              Added a check for state closed when changing Port, Proto and Addr.
Oct 22, 1997  V2.08 Added Flush method (asked by john@nexnix.co.uk) and
              FlushTimeout property (default to 60 seconds).
Oct 22, 1997  V2.09 Added SendFlags property to enable sending in or out of
              band data (normal or urgent, see RFC-1122)
Oct 28, 1997  V2.10 Added an OnLineTooLong event and code to handle the case
              where ReadLine has been called and the buffer overflowed (line
              long)
Oct 29, 1997  V2.11 Added DnsLookup functionnality (DnsLookup method, DnsResult
              property and DnsLookupDone event).
              Calling the connect method with a hostname work well except that
              it could block for a long period (ie: 2 minutes) if DNS do not
              respond. Calling the connect method with a numeric IP address will
              never block. So you can call DnsLookup to start hostname
              resolution in the background, after some time you evenutually
              receive the OnDnsLookupDone event. The copy the DnsResult property
              to the Addr property and call connect.
Oct 30, 1997  V2.12 added a check in DnsLookup to handel numeric IP which do
              not require any lookup. The numeric IP is treated immediately
              and immediately trigger the DnsLookupDone event.
              I modified the code to be compatible with Delphi 1.
Oct 31, 1997  V2.13 added CancelDnsLookup procedure.
Nov 09, 1997  V2.14 add LocalIPList function to get the list of local IP
              addresses (you have two IP addresses when connected to a LAN
              and an ISP).
Nov 11, 1997  V2.15 Made TCustomWSocket with virtual functions. This will
              allow to easily descend a new component from TCustomWSocket.
              Make ReadLine stop when the connection is broken.
Nov 12, 1997  V2.16 Corrected bug (Justin Yunke <yunke@productivity.org>)
              in LocalIPList: phe should be checked for nil.
Nov 18, 1997  Added ReceiveStr function (Suggested by FLDKNHA@danisco.com)
Nov 30, 1997  V2.18 Added a call to OnDnsLookupDone when canceling.
Dec 04, 1997  V2.19 Added LocalPort property and SessionConnected event
              for UDP socket.
              V2.20 Modified MessageLoop and ProcessMessages to process not
              only the socket messages, but all messages (necessary if the
              thread has several TWSocket for example).
Dec 09, 1997  V2.21 Corrected a minor bug in ReceiveStr. Detected by
              david@e.co.za (David Butler).
Dec 10, 1997  V2.22 Corrected a minor bug in Send which now correctly
              returns the number of bytes sent. Detected by
              james.huggins@blockbuster.com
Dec 16, 1997  V2.23 Corrected a bug which prevented the receiving of datagram
              from a UDP socket.
              Thank to Mark Melvin (melvin@misrg.ml.org) for pointing it.
Dec 20, 1997  V2.24 Added the PeekData function as suggested by Matt Rose
              mcrose@avproinc.com
Dec 26, 1997  V2.25 Added the Text property as suggested by Daniel P. Stasinski
              <dse@pacific.net>. Made GetXPort work even when listening as
              suggested by is81024@cis.nctu.edu.tw.
Jan 10, 1998  V2.26 Check for null hostname in DNSLookup
              Added DnsResultList with all IP addresses returned form DNS
Jan 13, 1998  V2.27 a Added MultiThreaaded property to tell the component that
              it is working in a thread and should take care of it (call
              internal ProcessMessages in place of Application.ProcessMessages,
              and do not use the WaitCtrl object).
Jan 15, 1998  V2.28 WMAsyncSelect revisited to work properly with NT winsock 2.
Feb 10, 1998  V2.29 Added an OnError event. If not assigned, then the component
              raise an exception when the error occurs.
Feb 14, 1998  V2.30 Published Text property
Feb 16, 1998  V2.31 Added virtual methods to trigger events
              Renamed all event handler variable to begin with FOn
Feb 26, 1998  V2.32 Added procedure PutDataInSendBuffer and PutStringInSendBuffer
              Using PutDataInSendBuffer you can place data in the send buffer
              without actualy trying to send it. This allows to place several
              (probably small) data chunk before the component attempt to send
              it. This prevent small packet to be sent. You can call
              Send(nil, 0) to force the component to begin to send data.
              If the buffer was not empty, PutDataInSendBuffer will just queue
              data to the buffer. This data will be sent in sequence.
Mar 02, 1998  V2.33 Changed the error check with WSAstartup as pointed out by
              Donald Strenczewilk (dstrenz@servtech.com)
Mar 06, 1998  V2.34 Added a runtime property to change the buffer size.
Mar 27, 1998  V2.35 Adapted for C++Builder 3
Apr 08, 1998  V2.36 Made SetDefaultValue virtual
Apr 13, 1998  V2.37 Reset FDnsLookupHandle to 0 after a failed call to
              WSACancelAsyncRequest
Apr 22, 1998  V2.38 Published AllSent property to let outside know if our
              buffer has some data unsent.
Apr 28, 1998  V2.39 Added LingerOnOff and LingerTimeout. Default values are
              wsLingerOn and timeout = 0 to behave by default as before.
              This value is setup just before Connect. Call SetLingerOption to
              set the linger option on the fly (the connection must be
              established to set the option). See winsock.closesocket on line
              help (winsock.hlp or win32.hlp) for a dsicussion of this option
              usage.
May 06, 1998  V2.40 Added a workaround for Trumpet winsock inet_addr bug.
              Thanks to Andrej Cuckov <andrej@cuckov.com> for his code.
May 18, 1998  V2.41 Jan Tomasek <xtomasej@feld.cvut.cz> found that Trumpet
              Winsock (Win 3.11) has some bugs and suggested a workaround in
              TryToSend procedure. This workaround makes TWSocket blocking in
              some cases. A new property enables the workaround. See code.
Jun 01, 1998  V2.42 In finalization section, check for not assigned IPList.
Jun 15, 1998  V2.43 Added code to finalization section to unload winsock if
              still loaded at that point (this happend if no socket where
              created but WinsockInfo called). Suggested by Daniel Fazekas
              <fdsoft@dns.gyor-ph.hu>
Jun 27, 1998  V2.44 Added checks for valid arguments in SetPort, SetProto
              and SetAddr. Deferred address resolution until Connect or Listen.
Jul 08, 1998  V2.45 Adadpted for Delphi 4
Jul 20, 1998  V2.46 Added SetWindowLong(FWindowHandle, 0, 0) in the destructor
              and a check for TWSocket class in XSocketWindowProc.
              Added virtual method RealSend.
Jul 23, 1998  V2.47 Added a TriggerSessionClosed from TryToSend in case of
              send error. This was called before, but with a nul error argument.
              Now it correctly gives the error number.
              Added a trashcan to receive data if no OnDataAvailable event
              handler is installed. Just receive the data and throw it away.
              Added reverse dns lookup asynchronous code (IP -> HostName).
              Thanks to Daniel Fazekas <fdsoft@dns.gyor-ph.hu> for his code.
Jul 30, 1998  V2.48 Changed local variable "error" by FLastError in SocketError
              to make it available from the OnError handler. Thanks to
              dana@medical-info.com for finding this bug.
              In Abort procedure, deleted all buffered data because it was send
              the next time the socket is opened !
              Added CancelDnsLookup in Abort procedure.
Aug 28, 1998  V2.49 Made InternalClose and ReceiveStr virtual
Sep 01, 1998  V2.50 Ignore CancelDnsLookup exception during destroy
Sep 29, 1998  V2.51 In InternalClose, protect AssignDefaultValue with
              try/except because SessionClosed event handler may have destroyed
              the component.
Oct 11, 1998  V2.52 Changed Shutdown(2) to Shutdown(1) in Internal Close to
              prevent data lost on send. You may have to call Shutdown(2) in
              your own code before calling Close to have the same behaviour as
              before.
              Changed argument type for ASyncReceive and passed 0 from FD_CLOSE
              message handler.
Oct 28, 1998  V2.53 Made WSocketLoadWinsock and WSocketUnloadWinsock public.
Nov 11, 1998  V2.54 Added OnDisplay event for debugging purpose
Nov 16, 1998  V2.55 Ignore WSANOTINITIALIZED error calling CloseSocket. This
              occurs when using TWSocket from a DLL and the finalization
              section is called before destroying TWSocket components (this is
              a program logic error).
              Made some properties and methods protected instead of private.
              Made some methods virtual.
              Added an Error argument to InternalClose.
              Added DoRecv virtual function.
              Added WSocketResolvePort
              Added WSocketResolveProto
              Deferred port and protocol resolution until really needed
              Transformed Listen to procedure (in case of failure Listen
              always calls SocketError which triggers an exception or the