Start Application Service on Windows Platform

To start an Application Service on the Windows platform, an EXE wrapper for the Application Service Listener function should be generated. See Implementing an Application Service Listener for details on how to do this.

Before starting the Application Service make sure that the DWA Windows run-time dll (WsydDwa21.dll ) has been copied to either the folder where the Application Service resides or to somewhere in the system path (e.g \WinNT\System32).

Parameters to Application Service

There are two ways to transfer parameters to the Application Service: Through the Application Service Listener INI file or by specifying arguments on the command line.

INI file parameters

When the INI-file is used to configure the Application Service the following parameters should be added to the HTML section of the INI file in addition to the standard parameters in the INI file as shown in the samle configuration below:
 

[HTML]
WEBSYDIANSERVER_PORT	           = 8189
WEBSYDIANSERVER_IPADDR	           = 127.0.0.1
SERVICE_URL	                   = wsydwa://127.0.0.1:11001/WEBDEMO
AUTO_RECOVER	                   = Y
TIME_TO_LIVE	                   = 3600
SOCKET_TIME_OUT	                   = 0
WEBSYDIANSERVER_CONNECTION_TIMEOUT = 30

For a description of each parameter please look at Application Service Options.

When the INI-file has been configured, the Application Service is started by executing the EXE-file.  Remember to start the Websydian Server before starting the new Application Service. Otherwise the Application Service will fail to initialize when attempting to connect to the Websydian Server.

When the Application Service has started successfully, it will deliver it's own Token to the Websydian Server. This can be verified by looking in the Websydian Server log file when the log level is set to TRACE or INFO.

For backward compatibility the following parameters can be used instead of the SERVICE_URL parameter:
 

SERVICE_PORT	= 11001
SERVICE_NAME	= WEBDEMO
SERVICE_IPADDR	= 127.0.0.1

If both methods are used the URL notation has higher precedence.

Command-line parameters

As with all Plex generated EXE files the Application Service Listener EXE can be executed from a command prompt and input parameters transferred as command-line arguments. The syntax is:

ASL <Dll> <Impl name> <Return> <Websydian Server IP> <Websydian Server port> <Websydian Server encoding> <Websydian Server connection> <IP> <port> <Service name> <Time to live> <Service URL> <Socket time out> <Recover> <Encoding> <Default character set>

Parameter	Description
ASL	Name of the Application Service Listener executable file
Dll	Name of the Application Service Listener dll file
Impl name	Plex implementation name of the Application Service Listener function
Return	*Returned status field. Any value can be inserted here
Websydian Server IP	IP address of the machine where the Websydian Server is started
Websydian Server TCP	TCP port that the Websydian Server listens on
Websydian Server encoding	Encoding used when communicating with the Websydian Server
Websydian Server connection	Time in seconds Application Service will wait before reconnecting to the Websydian Server
IP	IP address of the Application Service Listener
Port	TCP port used by the Application Service Listener
Service name	Application Service Name
Time to live	Token time to live
Service URL	Alternative to the IP, Port, and Service name parameters. The syntax is "wsydwa://<IP>:<Port>/Service name"
Socket time out	Time out on the socket connections
Recover	Automatic recovery from minor errors (Y or N)
Encoding	Not used on the Window platform
Default character set	Not used on the Window platform

Example:

dwasvc dwasvc dwasvc - 127.0.0.1 8189 " " 30 "<default>" 11001 myApp 0 " " 0 Y " " " "

The sequence " " is used to send a blank value ( *Blank ).

How to find reported errors

By default the Application Service will send errors to the stderr device. In order to be able to read this it is possible to redirect stderr to a file when launching the application service. This is done by appending a redirect command to the end of the command that launches the Application Service.

dwasvc [optional command line parameters] 2> error.txt

With the above command eventual errors will be written to the file error.txt.

Start Multiple Application Services.

In the previous section it was documented how to start a single instance of an Application Service. In a real world DWA system, this is a very unlikely scenario since an application is capable of handling only as many simultaneously HTTP requests as there are Application Services.

It is not possible to start multiple instances by simply activating the same executable as the second instance of the Application Service then will try to listen on the same TCP port that is occupied by the first instance - which will result in a failure of the second instance.

One approach is to use command-line arguments. Since it can be cumbersome to specify all these parameters and because only the port differs from each Application Service, it is only necessary to specify parameters up to the Port argument.

Example:

listener.exe listener listener - 127.0.0.1 8189 " " localhost 11001

It is assumed that the implementation name and file name of the Application Service Listener function is listener.

When starting a new instance of the Application Service the last port value should be changed so a new TCP port is used.

Another approach is to make a copy of the Application Service Listener executable and INI files and then launch the different instances using the following approach:

listener1.exe listener listener
listener2.exe  listener listener
...