TDDEMLClient / TDDEMLServer

Sources: source/classes/tddemlcl.prg, source/classes/tddemlsv.prg

Standalone classes

The DDE Management Library (DDEML) classes provide a high-level interface to Windows Dynamic Data Exchange using the DDEML API. TDDEMLClient connects to DDE servers and executes commands or requests data; TDDEMLServer registers a DDE server that responds to client requests. Both classes handle conversation management, service/topic registration, and data transfer through the DDEML protocol.

TDDEMLClient

TDDEMLClient connects to an existing DDE server, sends commands, and requests data.

Key DATA

DATA	Type	Description
`hInst`	Numeric	DDEML instance handle
`hConv`	Numeric	Conversation handle after successful connect
`cService`	Character	Service name string
`hService`	Numeric	Service handle
`cTopic`	Character	Topic name string
`hTopic`	Numeric	Topic handle
`nTimeOut`	Numeric	Timeout in milliseconds for DDE operations

Key METHODs

Method	Description
`New()`	Create DDE client and initialize DDEML
`Connect( cSvc, cTopic )`	Connect to a DDE server on the given service/topic
`Disconnect()`	Terminate the DDE conversation
`Execute( cCmd )`	Send a command string to the server for execution
`Request( cReq )`	Request data from the server; returns result string
`NetConnect( cSvr, cApp )`	Connect to a DDE server on a remote network machine

TDDEMLServer

TDDEMLServer registers as a DDE server, listening for client connections and responding to execute/request operations.

Key DATA

DATA	Type	Description
`hInst`	Numeric	DDEML instance handle
`aClients`	Array	Array of connected client conversation handles
`bOnConnect`	Block	Codeblock evaluated when a client connects
`bOnRequest`	Block	Codeblock evaluated when a client requests data; returns result
`bOnDisconnect`	Block	Codeblock evaluated when a client disconnects
`bOnExecute`	Block	Codeblock evaluated when a client sends a command

Key METHODs

Method	Description
`New()`	Create DDE server and initialize DDEML
`Connect()`	Register the server's service name and start listening
`ConnectConfirm( hConv )`	Accept and confirm a client conversation
`Disconnect( hConv )`	Terminate a client conversation
`Execute( cCmd )`	Process a command sent by a client
`Request( cReq, cTopic )`	Handle a data request from a client; returns result string
`SetNetDDE( lOn )`	Enable or disable network DDE support
`_Return( cData )`	Return data to a client request; returns hData handle

Example: Server and Client DDE

#include "FiveWin.ch"

// Server-side
function DdeServer()

   local oServer := TDDEMLServer():New()

   oServer:bOnConnect := { |hConv| ;
      QOut( "Client connected: " + Str( hConv ) ) }

   oServer:bOnRequest := { |cReq, cTopic| ;
      "Server received: " + cReq }

   oServer:bOnExecute := { |cCmd| ;
      QOut( "Executing: " + cCmd ) }

   oServer:Connect()

return oServer

// Client-side
function DdeClient()

   local oClient := TDDEMLClient():New()

   if oClient:Connect( "MyService", "MyTopic" )
      oClient:Execute( "[SAVE]" )
      ? oClient:Request( "GetData" )
      oClient:Disconnect()
   endif

   oClient:End()

return nil

Notes

Both classes require the Windows DDEML library (USER32.DLL). Initialize with DdeInitialize() and clean up with DdeUninitialize().
The Request() method on the client side returns a character string. On the server side, Request() should return the data to be sent, and _Return() packages it into a DDEML data handle.
Use NetConnect() on the client to connect across machines via Network DDE (requires Network DDE to be enabled on both systems).
Server callback blocks receive the conversation handle as a parameter, allowing multi-client management via the aClients array.

TDDEMLClient / TDDEMLServer

TDDEMLClient

Key DATA

Key METHODs

TDDEMLServer

Key DATA

Key METHODs

Example: Server and Client DDE

Notes

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