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DDServer Control for Visual Basic

Properties, methods, events, types and constants

You can read the full details by downloading the control and reading the help file, from which the diagram is taken. The boxes are all hyperlinks in the help file. The diagram shows the main components of the control from a functional point of view. Use the object browser in the Visual Basic development environment for a syntactic view.

  • The control has a collection of Services, each of which has a collection of Topics, each of which in turn has a collection of Data Items.
  • The System Topic of each Service is created and maintained semi-automatically.
  • The server application creates other Topics and may remove any Topic including the System Topic.
  • The Data Item objects allow the application to treat the data as a string or any binary format

The User Control

FailedReturnString User definable error return string
idInst The DDEML instance handle
LogFile The class managing the log file
ServerConvs The class managing the ServerConv collection
Services The class managing the Service collection
StateDescription The status enumeration as a string
SZDDE_ITEM_ITEMLIST The Item name of the Item list of a non-System Topic
SZDDESYS_ITEM_FORMATS The System Topic Item name of the format list
SZDDESYS_ITEM_HELP The System Topic Item name of the help text
SZDDESYS_ITEM_RTNMSG The System Topic Item name of the return message
SZDDESYS_ITEM_STATUS The System Topic Item name of the server status
SZDDESYS_ITEM_SYSITEMSThe System Topic Item name of list System Topic Items
SZDDESYS_ITEM_TOPICS The System Topic Item name of list Topics
SZDDESYS_TOPIC The standard name of the System Topic
Version The DDServer version string
CDMLERR Converts a DDEML error code to an enumerated value
ConvKey Converts a DDEML hConv to a key
Disconnect Destroys a DDE conversation
Enumerate Lists all the conversations, Topics and Items
GetLastError Returns the last DDEML error
Initialise Initialises the DDEML library
QueryString Returns the string for a string handle
ShowAboutBox Shows the "About" dialog
Uninitialise Cleans up all Services and the DDEML library
DDEAdviseRequest A client has started an advise or request loop
DDEAdviseStop A client has stopped an advise or request loop
DDEConnect A client has established a conversation
DDEDisconnect The server or client has disconnected a conversation
DDEExecute A client has issued an Execute command
DDENewAdviseRequest A client wants an advise on a Data Item not currently available
DDENewDataRequested A client has requested a Data Item not currently available
DDEPoke A client has poked some data
DDERegister A server has registered its Service name
DDEUnregister A server has unregistered its Service name
LogFileError An error has occurred in the log file
ServerConv A single DDE conversation
Service Encapsulates a DDE Service
Topic Encapsulates a Topic provided by a Service
DDSVData DDE data in string and binary format
LogFile Handles logging output
Types, constants and enumerated values
ConvContext A property of a conversation
QualityOfService A property of a conversation
LogFileOptionsEnum Logging output options
ExecuteResult The possible results of an Execute command
DMLERREnum DDEML error codes
Constants Various enumerated values

The Service object

The Service class encapsulates a DDE Service. The name of the Service is sometimes referred to as the Application, because many applications use their name as their only DDE Service name. DDServer supports any number of Services. The Service class manages the Topic collection. The Topics in the collection can be iterated with a 'For Each' loop.

hszServiceThe string handle of the Service name
ServiceNameThe Service name used by clients to connect
TopicCountThe number of Topics in the collection
TopicNamesA list of the Topics in the collection
CreateSystemTopicCreates the System Topic or updates it.
CreateTopicCreates a Topic and adds it to the collection
RemoveTopicRemoves a Topic from the collection
TopicReturns a Topic from the collection

The Topic object

Each instance of the Service class maintains a collection of Topic objects. Each Topic maintains a collection of DDSVData Data Item objects available on that Topic. The programmer can enumerate the Items available in each Topic by a 'For Each' statement.

ItemCountThe number of Data Items in the collection
ItemNamesA list of the Data Items available in this Topic
TopicNameThe Topic name
UserDataFor the use of the server application
CreateItemCreates a Data Item and adds it to the collection
ItemReturns a Data Item from the collection
RemoveItemRemoves a Data Item from the collection

The Server Data object

DDSVData is the class which manages data made available by the server or poked by the client. The data may be stored and retrieved either as a binary data block, or as a string, or byte by byte.

A server can provide on the same Topic many Items which have the same Item name if they have different formats. A data object is identified by the combination of its TopicName, ItemName and Format.
DataArrayThe data viewed as an array of Byte values
DataStringThe data as a string
FormatThe Clipboard format of the data
ItemNameThe Item name
NotifyAllowedWhether or not advise/notify loops are allowed
NotifyRequestsThe number of advise or notify loops for the Item
PokeAllowedWhether or not a client is allowed to poke data
SizeThe length of the data in bytes
TopicNameThe Topic name
UserDataFor the use of the server application
CopyByAddressCopies the data to a given address
CopyByteArrayCopies the data to a Byte array
CopyIntegerArrayCopies the data to an Integer array
CopyLongArrayCopies the data to a Long array
NotifyClientsNotifies all clients that new data is available
StoreByAddressStores data in the object by address
StoreByteArrayStores a Byte array in the data object
StoreIntegerArrayStores an Integer array in the data object
StoreLongArrayStores a Long array in the data object

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