Remote objects
The isCOBOL Application Server can also work as a repository for backend programs that can be called from client machines. Programs running in stand-alone as well as program running on a client pc in Thin Client environment can call programs that reside on a server computer where an isCOBOL Application Server is running. This objective is achieved through a simple CALL Statement. The connectivity with the Application Server that hosts the remote objects is configured by setting
iscobol.remote.code_prefix.
Programs loaded from remote.code_prefix are executed server-side using server resources. These programs can communicate with the calling program through LINKAGE SECTION items. They cannot have a user interface, they cannot display anything and must not accept user input. Only backend programs can run correctly as remote objects.
C functions can’t be called remotely; only COBOL programs can. If you need to call a C function on the server, create a bridge COBOL program, install the bridge program on the server along with the C function and call the bridge program instead of calling the C function directly.
Only COBOL programs called synchronously with a Format 1
CALL are searched among remote objects. In order to call a remote program asynchronously, use the
C$ASYNCRUN routine.
Example.
Consider the following setting:
iscobol.remote.code_prefix=isc://192.168.0.1:10999 |
And the following statement:
CALL "PROG1" USING param-1, param2 GIVING rc. |
isCOBOL will try to load PROG1 from the local CLASSPATH and code_prefix first. If the program is not found, then isCOBOL will try to load PROG1 through an Application Server running on the ip 192.168.0.1 on port 10999. The program will be searched remotely in all the paths listed in the CLASSPATH and code_prefix of the remote machine (ip 192.168.0.1). If the program is still not found, then a "ClassNotFound" error is returned.
Any Exception thrown on the server is returned to the client, including the internal StopRunException, so that a client program can be interrupted when there is a STOP RUN statement or an exception (e.g. wrong linkage section) in the server program: in the former case the program will stop silently without showing any message.
iscobol.remote.code_prefix=iscp://192.168.0.1:10999 |
Using Aliases
Remote calls can be done through aliases. An alias is a logical name used client side to identify a specific program run with a specific configuration file.
In order to activate such feature for remote calls, the following property must be set in the server side configuration:
iscobol.as.call.use_aliases=true |
Aliases are defined in the server side configuration with properties in the format:
iscobol.as.call.alias.<alias_name>=<PROGRAM_NAME>,<configuration_file> |
For example, the following server configuration file defines two aliases
• the first alias runs the program PROG1 with the default configuration
• the second alias runs the program TEST with the configuration file /usr/test/config1.properties
iscobol.as.call.use_aliases=true iscobol.as.call.alias.utility1=PROG1 iscobol.as.call.alias.utility2=TEST,/usr/test/config1.properties |
On the client side the program calls the alias name instead of the program name. For example, if you want to run the TEST program remotely using the remote configuration file /usr/test/config1.properties, you will just do:
User Authentication