.. highlightlang:: us

.. index:: DdeCallback_Connect

.. _ddecallback_connect:

DdeCallback_Connect
===================

.. us.tag  DdeCallback_Connect ENGLISH

:ref:`DdeCallback_Connect` is called when a client wants to open a channel to
UniScript.

.. function::  bool = DdeCallback_Connect(ssService, ssTopic)

.. us.return

**Return Value**

*bool* is TRUE (1) when the channel was successfully opened and FALSE (0) if the
function was unsuccessful.

.. us.params

**Parameters**

.. uparam:: ssService

   *ssService* is a service name. For UniPlot, it is the name ``"UniPlotSL"``.

.. uparam:: ssTopic

   *ssTopic* is the topic name.

.. us.comment

**Comment**

The standard DDE callback function which is located in the
:file:`UniPlot/script/obj_dde.ic` file is only a function body. To use
UniPlot as a DDE server, you have to add code to this function.

.. us.example

**Example**

The following WORD-Basic program causes the UniScript function
:ref:`DdeCallback_Connect`, :ref:`DdeCallback_ConnectConfirm` and the function
:ref:`DdeCallback_Disconnect` to be called.

::

   Sub Main
       chan = DDEInitiate("UniPlotSL", "xyz")
       DDETerminate(chan)
   End Sub

The standard DDE callback functions in UniScript are only function bodies. They
produce the following output into the UniScript command window:

::

   ---Connect---
   Service: UniPlotSL, Topic: xyz

   ---ConnectConfirm---
   Conversation-No.: a000500, Service: UniPlotSL, Topic: xyz

   ---Disconnect---
   Conversation-No.: a000500

.. seealso::
   :ref:`overview-dde`,
   :ref:`DdeCallback_ConnectConfirm`,
   :ref:`DdeCallback_Disconnect`,
   :ref:`DdeCallback_Request`,
   :ref:`DdeCallback_Poke`,
   :ref:`DdeCallback_Execute`

:sub:`id-1560814`