EntireX Version 9.7 SEARCH   CONTENTS   |   PDF PAGE   PDF BOOKS   |   HOME   UP   PREV   NEXT
 —  EntireX Broker ACI Programming  —

Writing Applications: Client and Server

This document describes how to implement and program client and server applications with EntireX Broker. It covers the following topics:

See also Writing Applications: Attach Server and Writing Applications: Units of Work.

Overview of Communication Models

There are two communication models in EntireX Broker: client and server and publish and subscribe.

Top of page

Basic Concepts of Client and Server

Client-and-Server Application Components

In the client-and-server communication model there are two partner application components: a requesting partner (the client) and the partner satisfying the request (the server). The client identifies the required service through the names of the SERVER-CLASS, SERVER-NAME and SERVICE with which the partner has registered.

EntireX Broker allows multiple server application components to register the same service in order to satisfy processing requirements. In conversational requests, the client and the server are bound to each other for the duration of the conversation. In addition, a server application component can satisfy more than one request type after registering several class, server and service names.

An application component is not restricted to a single role as either client or server; it can perform the role of both client and server. It can therefore make requests for processing while also satisfying requests from other partner application components.

Conversationality

The EntireX Broker allows both non-conversational and conversational communication in order to meet the different requirements of connections between distributed application components.

Using EntireX Broker, an application may have more than one conversation active at the same time with the same partner or with different partners. Conversational and non-conversational modes can also be used simultaneously. The required mode of communication is always controlled by the application component that initiates the communication, that is, the client side.

Synchronicity

EntireX Broker makes possible both synchronous and asynchronous communication. EntireX Broker enables application components to combine synchronous and asynchronous communication as needed by the application. The terms synchronous and asynchronous correspond to the terms "blocked" and "non-blocked". See Blocked and Non-blocked Broker Calls.

Top of page

API-TYPE and API-VERSION

Both the API-TYPE and the API-VERSION fields must always be provided.

Value Bit Pattern Description
1 (x'01') The standard value for API-TYPE is 1 (x'01') and usable with all Broker stubs in all environments.

Note:
If any of the following conditions exist, you must install the Adabas CICS link module with the definition PARMTYP=ALL, using the ADAGSET macro.

  1. If you are using NET transport with CICSETB stub with send or receive buffers greater than 32 KB.

  2. If you are using NET transport with CICSETB stub and your application does not have a TWA.

Certain Broker functionality requires a minimum API-VERSION. Using publish and subscribe requires API-VERSION 8 or higher. For the highest available version of Broker, see API-VERSION. The send buffer and the receive buffer are passed as parameters to the EntireX Broker. Both buffers can occupy the same location.

See Broker ACI Control Block Layout for Assembler | C | COBOL | Natural | PL/I | RPG.

Both the API-TYPE and API-VERSION fields must be set correctly to ensure that Broker returns the correct value in ACI field ERROR-CODE. Otherwise, depending on your programming language and environment, a return code may not always be given.

See Call Format for Assembler | C | COBOL | Natural | PL/I | RPG.

Top of page

LOGON and LOGOFF

The LOGON and LOGOFF Broker functions are optional when using the client-and-server programming model in your application. However, we recommend that the application issues LOGON and LOGOFF function calls for the following reasons:

Example for programming language Natural:

/* Logon to Broker/LOGON
MOVE #FCT-LOGON TO #ETBCB.#FUNCTION
/*
CALL 'BROKER' #ETBAPI #SEND-BUFF #RECV-BUFF #ERR-TXT

Logoff example for programming language Natural:

/* Logoff to Broker/LOGOFF
MOVE #FCT-LOGOFF TO #ETBCB.#FUNCTION
CALL 'BROKER' #ETBAPI #SEND-BUFF #RECV-BUFF #ERR-TXT

Top of page

USER-ID and TOKEN

Identifying the Caller

USER-ID identifies the caller and is required for all functions except VERSION. The USER-ID is combined with an internal ID or with the TOKEN field, if supplied, in order to guarantee uniqueness, for example where more than one application component is executing under a single USER-ID.

Brokers identify callers as follows:

Restarting after System Failure

Warning:
USER and TOKEN must be specified by all publisher and subscriber applications where publication and subscription data is held in the persistent store.

The Broker provides a reconnection feature, using the TOKEN field in the ACI. If the application supplies a token along with USER-ID, the processing is automatically transferred when a request with the same user ID and token is received, either from the same process or from a different process or thread.

Specification of USER and TOKEN is necessary for reconnection with the correct user context after Broker has been stopped and restarted. This specification is also necessary to enable effective use of publish and subscribe, including recovery from system failures.

Managing the Security Token

If you are using EntireX Security, the application must maintain the content of the SECURITY-TOKEN field and not change this field on subsequent calls.

Top of page

Control Block Fields and Verbs

Basic Functionality of Broker API

This section describes the basic functionality of the Broker API. The following functions in the Broker API are fundamental to client-and-server processing. For full set of verbs relating to UOW processing, see Control Block Fields and Verbs.

ACI Syntax

Function Fields in EntireX Broker Control Block
DEREGISTER 
API = 1 or higher 
, BROKER-ID = BROKER-ID 
, USER-ID = user_id 
[, TOKEN = token] 
, SERVER-CLASS = class_name | *
, SERVER-NAME = server_name | *
, SERVICE = service_name    | *
[, OPTION = QUIESCE | IMMED ]
EOC 
API = 2 or higher 
, BROKER-ID = BROKER-ID 
, USER-ID = user_id 
[, TOKEN = token]
[, OPTION = CANCEL] 
, CONV-ID = conv_id | ANY  
[, SERVER-CLASS = class_name]
[, SERVER-NAME = server_name]
[, SERVICE = service_name]
RECEIVE 
API = 1 or higher 
, BROKER-ID = BROKER-ID 
, USER-ID = user_id 
[, TOKEN = token] 
, WAIT = n | YES | NO 
, CONV-ID = conv_id | NEW | OLD | ANY 
, SERVER-CLASS = class_name | *
, SERVER-NAME = server_name | *
, SERVICE = service_name    | *
REGISTER 
API = 1 or higher 
, BROKER-ID = BROKER-ID 
, USER-ID = user_id 
[, TOKEN = token] 
, SERVER-CLASS = class_name
, SERVER-NAME = server_name
, SERVICE = service_name
[, OPTION = ATTACH ]
SEND 
API = 1 or higher 
, BROKER-ID = BROKER-ID 
, USER-ID = user_id 
[, TOKEN = token] 
[, OPTION = DEFERRED] 
, WAIT = n | YES | NO 
, CONV-ID = conv_id | NEW 
, SERVER-CLASS = class_name
, SERVER-NAME = server_name
, SERVICE = service_name

Key ACI Field Names

The following table lists key ACI field names for implementing applications that use the client/server communication model. The other fields are available to identify partner programs, specify buffer lengths, convey error codes, etc.

See Broker ACI Fields for all fields.

ACI Field Name Explanation
SERVER-CLASS A client uses these fields to identify the service that it requires. A server uses this to offer a service.
CONV-ID Identifier to obtain and specify the conversation. Also used to determine communication mode: conversational or non-conversational. See Conversationality.
FUNCTION Function code for one of the verbs (see Key Verbs for FUNCTION Field).
OPTION Indication of specific Broker behavior, depending on the function.
WAIT Time value to specify blocking or non-blocking of the conversation. See Blocked and Non-blocked Broker Calls.

Key Verbs for FUNCTION Field

The following table lists the most important verbs for the FUNCTION field.

See Broker ACI Functions for a complete list of functions.

Verb Description
REGISTER Inform the EntireX Broker that a service is available.
RECEIVE Retrieve request from partner.
SEND Send reply to the partner.
EOC Terminate one or more conversations.
DEREGISTER Remove the availability of the service.

Top of page

Implementation of Client and Server Components

This example implements a simple non-conversational server and the appropriate client. The server is able to receive a request from the client and send back a reply. See Conversationality.

The following EntireX Broker functions are used to implement the server component:

Function Explanation
LOGON Log on the application to EntireX Broker.
REGISTER Inform EntireX Broker about the availability of a service.
RECEIVE Retrieve request from partner.
SYNCPOINT Commit the sending or acknowledgment receipts of a UOW and examine status.
SEND Send reply to the partner.
DEREGISTER Remove the availability of the service.
LOGOFF Log off the application from EntireX Broker.

The program flow of the client component is: 

LOGON USER-ID=user-id
SEND SERVER-CLASS=server-class,SERVER-NAME=server-name,SERVICE=service
LOGOFF USER-ID=user-id

The program flow of the server component is: 

LOGON
REGISTER SERVER-CLASS=server-class,SERVER-NAME=server-name,SERVICE=service
repeat
     RECEIVE SERVER-CLASS=server-class,SERVER-NAME=server-name,SERVICE=service
     (individual request processing: reply to client for each message)
     SEND CONV-ID=n
end-repeat
DEREGISTER SERVER-CLASS=server-class,SERVER-NAME=server-name,SERVICE=service
LOGOFF

The example above illustrates the structure of a typical server program. It consists of a server registration and a loop with RECEIVE / SEND cycles. This RECEIVE / SEND loop is normally interrupted by shutdown messages from administration programs.

The appropriate client component needs three functions:

Function Explanation
LOGON Log on the application to EntireX Broker.
SEND Send request to partner.
LOGOFF Log off the application from EntireX Broker.

The service offered by the server above is used by issuing a SEND operation within the client component of the application.

Both server and client perform a LOGON as the first call and LOGOFF as the last call. This enables security checks and saves resources in EntireX Broker.

Top of page

Blocked and Non-blocked Broker Calls

The application can use the EntireX Broker control block field WAIT to determine whether Broker will automatically generate a WAIT in order for the command to be received or satisfied by the partner application.

Non-blocked Command: WAIT=NO

Blocked Command: WAIT=YES or WAIT=n

Examples: WAIT

The EntireX Broker allows both server and client applications to specify a WAIT time with the SEND or RECEIVE function. WAIT is a field in the ACI control block (see Broker ACI Fields). If a WAIT time is specified, the application is suspended until a reply is received or the timeout value has elapsed. If a timeout occurs, the EntireX Broker returns an error code to the calling program. If no WAIT time is specified, the application continues processing and collects the reply later.

Server applications typically use the WAIT field with a RECEIVE function in order to wait for requests. WAIT is not typically used with server SEND functions, allowing the server to continue processing instead of waiting for a request. For example: 

LOGON
REGISTER service
repeat
     RECEIVE,CONV-ID=NEW,WAIT=nS
     (individual processing)
     SEND,CONV-ID=n,WAIT=NO
end-repeat
DEREGISTER service
LOGOFF

Client applications use the WAIT field with a SEND function in non-conversational communication if they require a reply. Because the mode is non-conversational, no conversation ID is returned to the client. The client must therefore wait for the reply from the server. 

LOGON
SEND,CONV-ID=NONE,WAIT=nS
LOGOFF

A RECEIVE function with no WAIT time can be used to check if requests or data/messages are available for processing. Control is returned to the caller even if no request or data/message is available to satisfy the caller's operation. Appropriate error codes are returned when nothing is available. 

LOGON
RECEIVE,CONV-ID=n,WAIT=NO
LOGOFF

The application can use the EntireX Broker control block field WAIT in the following ways to determine whether Broker will automatically generate a WAIT in order for the command to be received or satisfied by the partner application.

Examples: Programming Language Natural

Note:
See Examples for EntireX Broker Tutorial.

Top of page

Conversational and Non-conversational Mode

The mode of communication is always controlled by the component of the distributed application that initiates communication. In the client and server model, this is the client side. When starting a communication, the CONV-ID field of the ACI control block is used to signal the communication mode to the Broker as follows:

The server always retrieves the unique conversation ID and uses it when sending back the reply to the client. If no reply is required in non-conversational mode, the server ignores the conversation ID.

Non-conversational Mode

When implementing a non-conversational communication, the CONV-ID field is used by the server as follows: 

LOGON
REGISTER service
repeat
     RECEIVE,CONV-ID=NEW 
     (individual processing)
     SEND,CONV-ID=n
end-repeat
DEREGISTER service
LOGOFF

The client's SEND function is supplemented as follows: 

LOGON
SEND,CONV-ID=NONE
LOGOFF

Conversational Mode

When implementing conversational communication, the server uses the CONV-ID field as follows: 

LOGON
REGISTER service
repeat
     RECEIVE,CONV-ID=NEW 
    repeat
         (individual processing)
         SEND,CONV-ID=n
         RECEIVE,CONV-ID=n 
    end-repeat until conversation ended
end-repeat
DEREGISTER service
LOGOFF

The conversation is ended when Message Class 0003 - EntireX ACI - Conversation Ended is received. See Error Handling.

The client's SEND function is supplemented as follows: 

LOGON
SEND,CONV-ID=NEW
SEND,CONV-ID=n
SEND,CONV-ID=n
EOC,CONV-ID=n
LOGOFF

EOC Reason

The reason for an EOC might be of interest to the partner of the conversation. EntireX Broker enables you to define the CANCEL option for an EOC function to indicate an abortive end of conversation. You can also distinguish between a timeout and a regular EOC on the basis of the error number. The error class is always Message Class 0003 - EntireX ACI - Conversation Ended; the error number specifies the actual circumstances.

Examples: Programming Language Natural

Note:
See Examples for EntireX Broker Tutorial.

Top of page

Managing Conversation Contexts

It is possible to program a server application to handle several clients simultaneously and thus many conversations in parallel. Such a server is also capable of providing several different services and this technique can be used to reduce the number of different server applications executing on your machine. This increases throughput without wasting resources on a new service replica. The following features make it easier to implement a server that supports multiple conversations:

Conversation Status

The Broker ACI control block contains a field named CONV-STAT. This is filled by Broker after a RECEIVE command. The following values are possible:

Value Description
NEW This is a new conversation. If the server needs to allocate a user-specific area, for example, this can be done without a comparison being made against existing conversations.
NONE This message is a conversationless message. It is probably not necessary to create a user context, since the next request of this user is completely independent of this one, which is a requirement of conversationless communication. The implementation of mixed servers (conversational and non-conversational) is easier if it is known whether a message is conversational or not.
OLD The message belongs to an existing conversation. The server can refer to the conversation user data to find the partner context. See Conversation User Data.

Conversation User Data

Servers capable of serving multiple clients simultaneously are either stateless (servicing non-conversational requests) or they have to store conversation-related data for each user. This conversation-related context data is typically stored by the server application in a dynamic memory area. When a message is received, the user context related to that conversation must be located. This can be done by implementing a mapping structure in the application that can be indexed by the conversation ID, which returns the related context data.

Additionally, conversation-related contexts can be maintained by the Broker on behalf of the server application using the USER-DATA field in the ACI control block. Broker remembers information stored in the USER-DATA field when executing the SEND command. This data is returned to the application on subsequent RECEIVE commands executed within the same conversation. Therefore, your application is able to store information in USER-DATA when executing SEND commands and retrieve it on RECEIVE commands. The data in USER-DATA is considered binary and is untouched by the Broker.

Note:
The USER-DATA is never transmitted from client to server or vice versa. Both sides of a conversation can store different USER-DATA, and both sides always receive their own data.

This USER-DATA helps with context areas as follows. A server application encounters a new conversation with the CONV-STAT API field. The user area is created and, typically, a first application confirmation is sent back to the client. Along with this SEND function, the server specifies the pointer to the user context - or the index into a context array, or whatever is available - into the USER-DATA. Whenever another request/message comes from that client via this conversation, this pointer/index is returned to the application, and the server has the context of the client application immediately, without having to scan a list of known conversations. Example: 

* example of State-ful server program which utilizes
* USER-DATA to maintain application specific context
* information between successive messages within
* conversations with clients.

REGISTER #SERVER-CLASS #SERVER-NAME #SERVICE

  DO FOREVER
    RECEIVE #CONV-ID=ANY
    DECIDE ON FIRST VALUE #ERROR-CODE
      /* ============================
      /* NICE RETURN CODE
      VALUE '0'
        DECIDE ON FIRST VALUE #CONV-ID
          /* ========================
          /* NEW CONVERSATION
          VALUE 'NEW'
            #REQUEST-IN = #RECEIVE-BUFFER
            ... PROCESS NEW REQUEST FROM CLIENT AND
                REPLY TO CLIENT ASKING BROKER TO REMEMBER
                ACCOUNT NUMBER SO CLIENT DOESN'T HAVE TO
                TRANSMIT THIS WITH EVERY MESSAGE
            #ACCOUNT-NR = REQUEST-IN.ACCOUNT-NR
            SEND #CONV-ID #SEND-DATA #USER-DATA
          /* ========================
          /* EXISTING CONVERSATION
          NONE VALUE
            /* NEXT MESSAGE IN CONVERSATION RECEIVED
            /* AND ACCOUNT NUMBER REMEMBERED BY BROKER
            #ACCOUNT-NR = #USER-DATA
            #REQUEST-IN = #RECEIVE-BUFFER
            ... DO SOME PROCESSING BASED ON REQUEST AND
                ACCOUNT NUMBER REMEMBERED BY BROKER FOR
                THIS CONVERSATION CONTEXT
            ... REPLY TO CLIENT AS APPROPRIATE AND
                END CONVERSATION SOONER OR LATER
            SEND #CONV-ID #SEND-DATA #USER-DATA
        END-DECIDE
      VALUE '00740074'                 /* RECEIVE TIME-OUT
        ESCAPE BOTTOM               
      NONE VALUE                       /* REAL BROKER ERROR
        ... DEAL WITH A REAL BROKER ERROR
    END-DECIDE
  DOEND /* END FOREVER LOOP

DEREGISTER

Stored EOC

Servers that handle multiple conversations in parallel normally have to maintain a user context related to every conversation as described above. However, this context is typically allocated dynamically, and is therefore released after the conversation has ended. Not knowing when a particular conversation has finished would result in orphan contexts. To avoid this, the Broker offers the NOTIFY-EOC option, which is a service-specific attribute defined in the Broker Attributes.

This means that the EOC notification, even for timed-out conversations, is kept until the server receives it. This is useful for servers serving multiple conversations, since they are always informed about the end of a particular conversation and can therefore release all internal resources of a particular user context.

Specification of NOTIFY-EOC=YES can consume substantial system resources; as a result, a shortage of conversations for a service may occur. To avoid this shortage, a server must issue RECEIVE requests not restricted to any conversation, which gives the Broker the chance to report timed-out conversations. This does not of course mean that only RECEIVE functions with CONVERSATION-ID=ANY are valid, but from time to time such an unrestricted RECEIVE function should be issued.

Top of page

Delayed SEND Function

To allow maximum flexibility in communication, the EntireX Broker provides a simple means of delaying the delivery of messages: allowing delivery of related messages in one logical block. If, for some reason, the messages that belong to a block cannot all be sent, all the messages in the logical block can optionally be deleted.

The mechanisms by which the EntireX Broker does this are the HOLD option on the SEND function and the UNDO function. Messages sent with HOLD status are not delivered until a message without the HOLD option is sent on the same conversation.

Example

This example illustrates the logical program flow of a client program that sends several messages on the same conversation, making delivery of the messages dependent on some condition. If the logical block of messages cannot be delivered (triggering an error condition), all messages in the logical block already sent can be deleted: 

SEND,CONV-ID=NEW,OPTION=HOLD
....                                /* individual processing
SEND,CONV-ID=n,WAIT=NO,OPTION=HOLD
....                                /* individual processing
SEND,CONV-ID=n,WAIT=NO,OPTION=HOLD
....                                /* individual processing
if <error> then                     /* error condition
    UNDO,CONV-ID=n,OPTION=HOLD
else
    SEND,CONV-ID=n,WAIT=NO
end-if          
....                                /* individual processing
EOC

Example: Programming Language Natural

Top of page

Timeout Parameters

Timeout Behavior

EntireX Broker provides a number of timeout mechanisms that allow you to control WAIT times flexibly, optimize resource usage, and configure efficient communication.

There is interplay between the WAIT values of your SEND and RECEIVE calls and the settings of the non-activity parameters in the Broker attribute file. See the WAIT field.

Types of Non-activity Time

There is interplay between the non-activity times specified in the attribute file for the attributes

where an application component performs more than one of these roles. In this case, the maximum non-activity time associated with the user will take precedence. This fact must be considered where an application component implements both publish and subscribe and client and server.

Recommendations

The following recommendations apply to developing client and server applications:

See also Timeout Considerations for EntireX Broker.

Unit of Work Lifetime

The UWTIME parameter in the Broker Attributes specifies the lifetime for a persistent UOW. The UOW exists until it has been successfully processed or until it is explicitly cancelled or backed out. If a UOW times out before being processed, or before any other explicit action is taken, its status changes to TIMEOUT. The status may or may not be retained in the persistent store, depending on the value of UOW status lifetime as described below. The default UOW lifetime for the Broker is defined by the UWTIME attribute. It can be overridden by the application in the UWTIME field of the ACI control block.

The UOW lifetime for the units of work is calculated only while Broker is executing.

Unit of Work Status Lifetime

This can be specified through either of the following two exclusive attribute settings. The default value zero implies the UOW status lifetime is zero, which means the status of the UOWSTATUS is not retained after one of the following events occurs: UOW is processed; UOW times out; UOW is backed out; UOW is cancelled. Status lifetime can be specified through either of the following two parameters in the Broker Attributes:

The status lifetime for the unit of work is calculated only while Broker is executing.

Note:
The values described here as UWSTATP and UWSTAT-LIFETIME can also be assigned as global Broker attributes or as a per-service attribute. However, the value specified by the application in the ACI control block overrides the Broker (or service) attributes. See Broker ACI Fields.

Top of page

Data Compression

Data compression within EntireX Broker allows you to exchange smaller packet sizes between senders and receivers. This helps to reduce response time during transmissions as well as improve the overall network throughput, especially with low bandwidth connections.

Compression is performed only on the buffers used to send and receive data. The application has the option of setting the level of compression/decompression for data transmission. The compression level can be set to achieve either no compression or a range of compression/decompression. See Data Compression in EntireX Broker. Application components can set compression individually to Broker.

zlib is a general-purpose software implementing data compression across a variety of platforms. The functions used within EntireX Broker represent a subset of those available within the zlib software. The compression algorithms are implemented through the open source software zlib. It may occur that the data buffer does not compress during a data transmission; if it does not compress, a logged warning message will appear in 00200450 and in the stub.

Technique

The Broker ACI control block contains a field that is used to set the compression level. This field determines for any send/receive transmission whether the data buffer will be compressed/decompressed. See ACI control block field COMPRESSLEVEL.

Top of page

Error Handling

After every broker operation, the application must check the ERROR-CODE. It consists of a combination of

While the error number describes the exact situation, the error class often determines how the program will proceed after returning from the EntireX Broker operation. From the programmer's point of view, therefore, the error class may be more important than the particular error number.

For more information, see Error Messages and Codes.

Programming Techniques

We recommend trapping the error classes in a "case" statement, for example, a DECIDE in Natural or a switch statement in C.

All error classes - for example user and configuration errors - leading to the same action (that is, reporting or logging the situation and aborting issuing broker calls), can be handled together in the NONE VALUE or default case.

Example for C Progamming Language

int   i, iErrorCode, iErrorClass, iErrorNumber, ret_val;
char  szErrorTextBuffer[S_TXT + 1];.....

/* prepare error code field and error text buffer */
memset(pETBCB->error_code,'0',sizeof(pETBCB->error_code));
memset(szErrorTextBuffer,'\0',sizeof(szErrorTextBuffer));

/* call the broker */
ret_val = broker(pETBCB,pSendBuffer,pReceiveBuffer,szErrorTextBuffer);

/* evaluate error class from error code field */
iErrorClass = 0;
for(i = 0; i < 4; ++i)
{  
    iErrorClass *= 10;
    iErrorClass += pETBCB->error_code[ i ] - '0';
}

if (iErrorClass == 0 && ret_val != 0)
{
    printf("Wrong API_TYPE and/or API_VERSION\n");
}
else
{
    /* evaluate error number from error code field */
    iErrorNumber = 0;
    for(i = 4; i < 8; ++i)
    {  
        iErrorNumber *= 10;
        iErrorNumber += pETBCB->error_code[ i ] - '0';
    }

    /* evaluate error code as integer value */
    iErrorCode = (iErrorClass * 10000) + iErrorNumber;

    /* handle error */
    switch (iErrorClass)
    {
        case 0: /* Successful Response */
            ....
            break;

        case 2: /* User does not exist */
            ....
            break;

        case 3: /* Conversation ended */
            ....
            break;

        case 7: /* Service not registered */   
            ....
            break;

        case 74: /* Wait Timeout occurred */
            ....        
            break;

        ....

        default:
            printf("EntireX Broker Error occurred.\n");
            printf("%8.8u %s",iErrorCode,szErrorTextBuffer);
            break;     
    }
}

Top of page

Using Internationalization

It is assumed that you have read the document Internationalization with EntireX and are familiar with the various internationalization approaches described there.

This section covers the following topics:

General Information

The broker stub does not convert your application data before it is sent to the broker. The application's data is shipped as given.

For the internationalization approaches ICU conversion and SAGTRPC user exit, valid locale strings are required for conversion to behave correctly.

Providing Locale Strings

Under the Windows operating system:

Under all other operating systems:

With the ACI control block field LOCALE-STRING:

The encoding in which your application gives the data to the broker stub and the locale string

otherwise, unpredictable results will occur.

Example for Assembler

MVC   S$LOCALE,=C'ECS037'                 MOVE CP
....

Examples for C

  1. Using a specific codepage 

    /* prepare the locale-string with a codepage */
memset (pETBCB->locale_string,' ',sizeof(pETBCB->locale_string));
strncpy(pETBCB->locale_string,"ECS0819",sizeof(pETBCB->locale_string));
....

  2. Using the platform's default codepage (Windows only) 

    /* prepare the locale-string with a codepage */
memset (pETBCB->locale_string,' ',sizeof(pETBCB->locale_string));
strncpy(pETBCB->locale_string,
ETB_CODEPAGE_USE_PLATFORM_DEFAULT,sizeof(pETBCB->locale_string));
....

Example for COBOL

MOVE 'ECS037' TO LOCALE-STRING.
....

Examples for Natural

MOVE 'ECS037' TO #SDPA-API.#LOCALE_STRING.
....

Using the ENVIRONMENT Field with the Translation User Exit

Using the internationalization approach translation user exit, an ACI programmer can provide additional information to their translation exit through the ENVIRONMENT field, allowing flexible translation behavior in accordance with application requirements. The field cannot be used for any other internationalization approaches and must be empty if a method other than translation user exit is used. See Translation User Exit.

Example

Assume a broker service or topic has a user-written translation routine called ABCTRAN, which is capable of performing several types of data conversion, for example EBCDIC-ASCII translation, byte swapping, and mixed data types. The user translation routine may need to know the data formats used by both partners. The ENVIRONMENT field can be used to pass this information from the application to the translation routine in Broker kernel.

Technique 

MOVE 'MYCODEPAGE' TO #ETBCB.#ENVIRONMENT
...
CALL 'BROKER' #ETBAPI #SEND-BUFF #RECV-BUFF #ERR-TXT

Top of page

Using Send and Receive Buffers

Introduction

The send buffer and the receive buffer are passed as parameters to the EntireX Broker. Both buffers can occupy the same location. See Call Format for Assembler | C | COBOL | Natural | PL/I | RPG.

The length of the data to be sent is given in the ACI field SEND-LENGTH. If the SEND-LENGTH is greater than the send buffer during data transmission, you could accidentally send the data that is physically located in memory behind your send buffer to the designated Broker.

The RECEIVE-LENGTH is required with the RECEIVE and RECEIVE_PUBLICATION functions and with SEND functions waiting for a reply. The length of the receive buffer is specified in the ACI field RECEIVE-LENGTH. If the RECEIVE-LENGTH is greater than the receive buffer during data reception, you can overwrite the data physically located behind the receive buffer being used.

If the data to be returned is less than RECEIVE-LENGTH, the rest of the receive buffer remains unchanged and is not padded with trailing blanks or other characters. The ACI field RETURN-LENGTH contains the length of the data actually returned. The RECEIVE-LENGTH field is not changed upon return.

Note:
With Adabas version 8, the maximum size of message data is no longer limited to approximately 32 KB. If Adabas version 8 is not used, these same limits still apply under z/OS.

Error Cases

Conversion and translation of data can increase the amount of data and thus require a buffer of a larger size than provided. It may also be impossible to determine the size required in advance. EntireX provides a feature to reread the data in such cases:

Using API version 2 and above, if the amount of data to be returned is greater than the RECEIVE-LENGTH, the exact length needed is given in the ACI field RETURN-LENGTH together with an error code, depending on the internationalization approach. See Internationalization with EntireX. Note the following:

For translation and translation user exit:

for ICU conversion and SAGTRPC user exit:

To obtain the entire message, increase the size of the receive buffer and issue an additional Broker ACI function RECEIVE or RECEIVE_PUBLICATION with the option "LAST".

Using API version 5 and above, it is also possible for a client to reread a truncated message in non-conversational mode, by issuing an additional Broker ACI function RECEIVE or RECEIVE_PUBLICATION with the option "LAST" as well as the CONV-ID returned from the ACI control block. No EOC is needed after RECEIVE.

Transport Methods

The maximum length possible for send and receive buffers is affected by the transport method used.

Transport Method Maximum Receive / Send Buffer Size If using this transport method, ...
TCP/IP 2,147,482,111 B

  • the maximum send and receive buffer size is approximately 2,147,482,111 bytes.

Entire Net-Work 30,545 B

  • the send and receive buffer sizes are affected by the setting of the Net-Work parameter IUBL for all involved platforms (see the Net-Work documentation for more information);

  • the send and receive buffer sizes are affected by the Adabas SVC/Entire Net-Work-specific attribute IUBL for Broker running under z/OS;

  • the maximum send and receive buffer size is around 30,545 bytes.

    Note:
    Under z/OS with Adabas version 8, the value for NET is the same as for TCP and SSL.

SSL 2,147,482,111 B

  • the maximum send and receive buffer size is approximately 2,147,482,111 bytes.

Top of page

Tracing

Trace information showing the commands help the application programmer debug applications and solve problems. Tracing can be obtained for the application (stub trace) and for the Broker kernel (kernel trace). The stub trace shows the Broker functions issued by your application, whereas the Broker kernel trace will contain all Broker functions issued by all applications using the Broker.

Setting the Broker attribute TRACE-LEVEL=1 provides traces containing just the Broker functions processed by the Broker kernel without additional diagnostics. It is only necessary to set the trace value higher when generating traces for Software AG support.

Stub Trace

Tracing is available for all stubs on UNIX and Windows. For the stubs for which tracing is available on z/OS, see table under Administering Broker Stubs.

To set the stub trace, see Tracing for Broker Stubs under z/OS | UNIX | Windows | z/VSE.

Kernel Trace

Tracing is available for Broker on all platforms. For z/OS, see Administering Broker Stubs.

To set the kernel trace, see Tracing webMethods EntireX under UNIX | Windows | BS2000/OSD | z/VSE.

Top of page

Transport Methods

Overview of Supported Transports

This table gives an overview of the transport methods supported by EntireX Broker stubs.

Operating System Environment Module Transport to Broker
TCP SSL NET (1) HTTP(S) (6)
z/OS (2) Batch, TSO, IMS (BMP) BROKER x x x  
Com-plete COMETB x (3) x  
CICS CICSETB x (3) x  
IMS (MPP) MPPETB x x x  
IDMS/DC (4) IDMSETB x (3)    
Natural NATETB23 x x x  
UNIX System Services Java ACI x x   x
UNIX broker.so x x    
Java ACI x x   x
Windows broker.dll (5) x x    
Java ACI x x   x
BS2000/OSD Batch, Dialog (formerly TIAM) BROKER x x x  
z/VSE Batch BKIMB x   x  
CICS BKIMC x   x  
z/VM BKIMBCMS x   x  
IBM i EXA x      
OpenVMS BROKER x x    

Notes:

  1. NET is available for transport to a broker running under mainframe platforms only; not to a broker running under UNIX or Windows.
  2. Under z/OS you can use IBM's Application Transparent Transport Layer Security (AT-TLS) as an alternative to direct SSL support inside the broker stub. Refer to the IBM documentation for more information.
  3. Use AT-TLS. See Note 2.
  4. Tracing and transport timeout are not supported in this environment.
  5. Stub broker32.dll is supported for reasons of backward compatibility. The functionality is identical to broker.dll.
  6. Via Broker HTTP(S) Agent; see Settting up and Administering the Broker HTTP(S) Agent under UNIX | Windows.

See also:

TCP/IP

TCP is not available for all Broker stubs and all environments (see table above).

See Using TCP/IP as Transport Method for the Broker Stub in Transport Methods for Broker Stubs under z/OS | UNIX | Windows | BS2000/OSD | z/VSE | z/VM, which describes how to set up TCP transport.

Application programs using TCP/IP as the transport specify the target Broker ID in terms of a host name (or IP address) together with the port number on which the Broker TCP/IP communications driver is listening. Example: An application communicating through TCP/IP would specify on each command the Broker ID 

IBM1:3932:TCP

where the host on which the Broker kernel executes is known to TCP as IBM1 and is listening on port 3932.

Entire Net-Work

Communication through Entire Net-Work is available for all Broker stubs when communicating with a Broker kernel on z/OS through Entire Net-Work. Applications can also utilize Entire Net-Work communication to obtain local interprocess communication with a z/OS Broker kernel running on the same machine as the application. This can provide a considerable performance benefit. Local interprocess communication is achieved through the Adabas SVC mechanism.

Application programs using Entire Net-Work as the transport specify the target Broker ID in terms of the target Entire Net-Work ID of the Broker kernel. For example, an application communicating through Entire Net-Work would specify on each command the Broker ID: 

ETB001::NET

This can be abbreviated to the following for the Assembler stubs executing on z/OS (BROKER, CICSETB, COMETB, MPPETB): 

ETB001

where the Entire Net-Work ID of the Broker kernel is 001.

SSL and TLS

Application programs using Secure Sockets Layer (SSL) or Transport Layer Security (TLS) as the transport must specify the SSL settings to the broker stub before any communication with the Broker can take place. There are various methods of setting SSL or TLS transport. See SETSSLPARMS and Running Broker with SSL or TLS Transport under z/OS | UNIX | Windows.

Example: An application communicating through SSL or TLS would specify on each command the Broker ID: 

MYPC:1958:SSL

where the host on which the Broker kernel executes is known to SSL or TLS as MYPC and is listening on port 1958.

Transport Examples

See table above for how SSL or TLS is supported depending on broker stub and platform.

For information on Secure Sockets Layer, see SSL or TLS and Certificates with EntireX.

Considerations for Writing Applications

Restrictions with API Versions 1 and 2

The following maximum message sizes apply to all transport methods:

Top of page

Variable-length Error Text

In previous ACI versions, Broker kernel always returned 40 bytes of error text, space-padded if necessary. For ACI version 9 and above, variable length error text can now be returned if requested. With ACI 9 and above, error text up to the requested length is returned via a new section in the ACI reply. For any previous ACI versions, ETXL is not sent, and the error text is returned by the traditional method.

Note that the error text will continue to be traced in the stub and kernel trace and kernel command log.

See Broker ACI Fields.

Top of page

Programmatically Turning on Command Logging

You can trigger command logging for EntireX components that communicate with Broker by setting the field LOG-COMMAND in the ACI control block.

All functions with LOG-COMMAND programmatically set in the ACI string field will have their commands logged, regardless of any filter settings. Because the LOG-COMMAND option will override any command-log filter settings, remember to reset the LOG-COMMAND field if subsequent requests do not need to be logged.

Top of page

 www.softwareag.com  Copyright © 1997-2014 Software AG, Darmstadt, Germany.   SEARCH   CONTENTS   |   PDF PAGE   PDF BOOKS   |   HOME   UP   PREV   NEXT