DDE and Name Settings

Cascade Connect: Version 4.0
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# 6.6. DDE and Name Settings

The DDE and Name Settings define the names of the data server, client, and tasks under the data server. All entries in these fields cannot contain spaces, and the data server names are case sensitive.

Figure 6-6. DDE and Name Settings

Cascade DDE Service works with Cascade DDE Topic (below) to identify Cascade Connect to the Windows client. You use these names when you are defining the DDE conversation in the Windows client program. Windows programs using DDE ADVISE loops require service and topic names when requesting data. This is done using the DDE `servicename|topic!variable` notation. When this link syntax is used, the service name of Cascade Connect is the name defined by this option. The default entry for this field is the string: `cascade`. The configuration file syntax is:

        myservice   DDE servicename

Cascade DDE Topic identifies the topic to the Windows client. (See above for more information.) The default entry for this field is the string: `data`. The configuration file syntax is:

        mytopic   DDE topicname

Client DDE Service works with Client DDE Topic (below) to instruct Cascade Connect as to what Windows client it will be communicating with. This information is used when Cascade Connect initiates the DDE conversation with the Windows client. This is the only service to which Cascade Connect will transmit using DDE POKE messages. There is no default entry for this field. The configuration file syntax is:

        clientservice   DDE servicename

Client DDE Topic is the DDE topic name registered by Cascade Connect's primary Windows client. This is the topic to which all DDE POKE messages will be addressed. There is no default entry for this field. The configuration file syntax is:

        clienttopic   DDE topicname

Most popular Windows programs support DDE. The service and topic names for some of them are:

Application | DDE Service Name | DDE Topic Name
--- | --- | ---
InTouch Viewer | VIEW | TAGNAME
MS-Excel | EXCEL | Name of the spreadsheet, chart, macro, etc. For example: mysheet.xls
MS-Access | MSACCESS | Name of Table, SQL query, or Macro to run.
MS-Word | WINWORD | MS-Word WINWORD Name of the document, including the .doc extension.
FIX DMACS | DMDDE | DATA
National Instruments' Lookout | LOOKOUT | Name of application, without the .lkp extension.
Asymetrix Toolbook | TOOLBOOK | Name of toolbook application (with .tbk extension)

Connect Server name is the name that the Connect Server uses to identify itself when it starts up. This is needed so that other data server tasks can send messages to it.

| Entry in this field is not necessary if the Cascade DataHub is being used.

The Connect Server can register a task name through the data server's nameloc facility, allowing any data server task to send messages to the Windows client. This option determines the name that will be registered.

| If more than one Windows client will be connecting to a machine on the network, each will require a dedicated instance of the Connect Server with its own, unique Connect Server name. The name locator will disallow duplicate name registrations.

There is no default entry for this field. The configuration file syntax is:

        qnxname   taskname
        qnxname   taskname
          .
          .
          .

Multiple entries are written one per line.

Server client name is the name of your custom program (such as the polling program described in If not using the Cascade DataHub) to which the Connect Server will pass messages, in lieu of the Cascade DataHub.

| Entries in this field are ignored if the Cascade DataHub is being used.

At start-up, the Connect Server first looks for the Cascade DataHub name server (nserve), and connects to it, whether or not a Cascade DataHub is actually running at that time. If nserve is found, then the entry in this field is ignored. There is no default entry for this field. The configuration file syntax is:

        qnxclient   taskname

TCP Heartbeat specifies the number of milliseconds that Cascade Connect will allow a TCP link to remain idle before transmitting an empty message, whose purpose is to maintain activity on the link. If other message traffic occurs during the heartbeat period, the heartbeat message will not be transmitted. It is in fact possible for the link to be idle for almost two heartbeat periods due to the implementation of the heartbeat algorithm. If this number is set to zero, then no heartbeat messages are generated. The default entry for this field is 0. The configuration file syntax is:

        tcpheartbeat   numberofmilliseconds

TCP Timeout specifies the number of milliseconds that the TCP link can be idle before it is deemed to be disconnected. If this timeout expires, the link will be dropped, and Cascade Connect will attempt to re-connect to the first available TCP host. It is in fact possible for the link to be idle for almost two timeout periods before the link is dropped due to the implementation of the timeout algorithm. Normally this timeout should be set to more than twice the TCP Heartbeat time. This timeout should also be long enough that a long-lasting Windows event such as a program starting up does not cause the traffic on the TCP link to be held up beyond the timeout period. If the timeout value is set to zero, the default TCP/IP timeout mechanism is used. The default entry for this field is 0. The configuration file syntax is:

        tcptimeout   numberofmilliseconds

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