COMMUNICATION ( ABAP Keyword) introduction & details

COMMUNICATION

Variants

1. COMMUNICATION INIT DESTINATION dest ID id.
2.
COMMUNICATION ALLOCATE ID id.
3. COMMUNICATION ACCEPT ID id.
4.
COMMUNICATION SEND ID id BUFFER f.
5. COMMUNICATION RECEIVE ID
id
…BUFFER f
…DATAINFO d
…STATUSINFO s.
6. COMMUNICATION
DEALLOCATE ID id.

The COMMUNICATION statement allows you to develop
applications which perform direct program-to-program communication. The basis
for this is CPI-C (Common Programming Interface – Coummunication), defined by
IBM within the context of SAA standards as a standardized communications
interface. The COMMUNICATION statement provides the essential parameters for
implementing simple communication. Its starter set covers the following
functionality:
Establishing a connection Accepting a communication Sending
data Receiving data Closing a connection
The other essential part of such a
communication is an ABAP/4 program containing a FORM routine which is executed
when the connection has been established. This program may be in an R/3 System
or an R/2> System. Here, you should be aware that the application programs
themselves declare a protocol. In particular, logon to the partner SAP System
must be performed in the calling program. The partner programs must also manage
different character sets, e.g. ASCII – EBCDIC themselves. A facility known as
the Remote Function Call ( RFC ) has now been developed to save users from
having to deal with these problems. External programs (e.g. a program written in
C on a UNIX workstation) can also be used as partner programs. For this purpose,
SAP provides a platform-specific development library. For more detailed
information about communication in the SAP System, you can refer to the
manual
SAP Communication: Programming
Further information about
communication can be found in any of the following literature:

IBM
SAA
Common Programming Interface
Communication Reference
SC
26-4399

X/Open Developers’ Specification CPI-C
X/Open Company
Ltd.
ISBN 1 872630 02 2

Variant 1

COMMUNICATION INIT DESTINATION dest ID id.

Addition

… RETURNCODE rc

Effect

Initializes a program-to-program connection.

The partner
system is specified in the dest field. You can use any name you like, but it
must be entered in the connection table TXCOM and can be no more than 8
characters long. This entry in TXCOM determines to which physical system a
connection is established using the symbolic name of the target
system.

In the field id , the system assigns an eight-character ID number
of type C to the connection. The system field SY-SUBRC contains an appropriate
return code value.
All return codes can be read using their symbolic names.
For this purpose, you can use the program RSCPICDF which contains these names
and can be included, if required.

Addition

… RETURNCODE rc

Effect

Stores the return code in the field rc .

Example

TYPES: CONVERSATION_ID(8) TYPE C,
     DESTINATION(8)     TYPE C,
     RETURN_CODE        LIKE SY-SUBRC.
DATA:  CONVID  TYPE CONVERSATION_ID,
     DEST    TYPE DESTINATION VALUE 'C00',
     CPIC_RC TYPE RETURN_CODE.
INCLUDE RSCPICDF.

COMMUNICATION INIT DESTINATION DEST
                 ID          CONVID
                 RETURNCODE  CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: /'COMMUNICATION INIT, RC = ', CPIC_RC.
 EXIT.
ENDIF.

Variant 2

COMMUNICATION ALLOCATE ID id.

Addition

As for variant 1.

Effect

Sets up a program-to-program connection. The call must
immediately follow COMMUNICATION INIT .

Example

TYPES: CONVERSATION_ID(8) TYPE C,
     DESTINATION(8)     TYPE C,
     RETURN_CODE        LIKE SY-SUBRC.
DATA:  CONVID  TYPE CONVERSATION_ID,
     DEST    TYPE DESTINATION VALUE 'C00',
     CPIC_RC TYPE RETURN_CODE.
INCLUDE RSCPICDF.

COMMUNICATION INIT DESTINATION DEST
                 ID          CONVID
                 RETURNCODE  CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: /'COMMUNICATION INIT, RC = ', CPIC_RC.
 EXIT.
ENDIF.
COMMUNICATION ALLOCATE ID CONVID RETURNCODE CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: /'COMMUNICATION ALLOCATE, RC = ', CPIC_RC.
 EXIT.
ENDIF.

Variant 3

COMMUNICATION ACCEPT ID id.

Addition

As for variant 1.

Effect

Accepts a connection requested by the partner program. id is a
field of type C which is 8 characters long and contains the ID of the accepted
connection after a successful call.

Example

FORM CPIC_EXAMPLE.
TYPES: CONVERSATION_ID(8) TYPE C,
       RETURN_CODE        LIKE SY-SUBRC.
DATA:  CONVID  TYPE CONVERSATION_ID,
       CPIC_RC TYPE RETURN_CODE.
INCLUDE RSCPICDF.
COMMUNICATION ACCEPT ID CONVID
                     RETURNCODE  CPIC_RC.
IF CPIC_RC NE CM_OK.
   EXIT.
ENDIF.
ENDFORM.

Variant 4

COMMUNICATION SEND ID id BUFFER f.

Additions

1. … RETURNCODE rc
2. … LENGTH len

Effect

Sends data to the partner program. The data is stored in the
field f which follows the key word parameter BUFFER . It is sent in the full
length of the field f . If the partner program is part of a system which has a
different character set, you must perform an appropriate conversion yourself. To
do this, use the TRANSLATE
statement.

Addition 1

… RETURNCODE rc

Effect

Stores the return code in the field rc .

Addition 2

… LENGTH leng

Effect

Sends the contents of the field f to the partner program in the
specified length.

Example

TYPES: CONVERSATION_ID(8) TYPE C,
     DESTINATION(8)     TYPE C,
     RETURN_CODE        LIKE SY-SUBRC.
DATA:  CONVID  TYPE CONVERSATION_ID,
     DEST    TYPE DESTINATION VALUE 'C00',
     CPIC_RC TYPE RETURN_CODE.
INCLUDE RSCPICDF.

COMMUNICATION INIT DESTINATION DEST
                 ID          CONVID
                 RETURNCODE  CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: /'COMMUNICATION INIT, RC = ', CPIC_RC.
 EXIT.
ENDIF.
COMMUNICATION ALLOCATE ID CONVID                        RETURNCODE
CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: /'COMMUNICATION ALLOCATE, RC = ', CPIC_RC.
 EXIT.
ENDIF.
RECORD = 'The quick brown fox jumps over the lazy dog'.
COMMUNICATION SEND ID     CONVID
                 BUFFER RECORD
                 LENGTH LENG
                 RETURNCODE CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: / 'COMMUNICATION SEND, RC = ', CPIC_RC.
 EXIT.
ENDIF.

Since
the length is specified explicitly in this example, only the part ‘ The quick
brown fox ‘ is transferred from the contents of the field RECORD .

Variant 5

COMMUNICATION RECEIVE ID id …BUFFER f …DATAINFO d
…STATUSINFO s.

Additions

1. … RETURNCODE rc
2. … LENGTH leng
3. … RECEIVED
m
4. … HOLD

Effect

Receives data in the field f . If no length is explicitly
defined, the amount of data accepted depends on the length of the field. The
fields d and s contain information about the receive process. You can address
the contents of these using symbolic names in the include program RSCPICDF . The
field d indicates whether the data was received in its entirety. The status
field s informs the RECEIVE user of the status of the program. Here, it is
important to know whether the program is in receive status or send status. It
is, for example, not possible to send data if the program is in receive
status.
For more detailed information about these protocol questions, refer
to the manuals listed above.

Addition 1

… RETURNCODE rc

Effect

Stores the return code in the field rc .

Addition 2

… LENGTH leng

Effect

Receives data only in the specified length leng .

Addition 3

… RECEIVED m

Effect

After the call, m contains the number of bytes received by the
partner program.

Addition 4

… HOLD

Effect

Normally, data is received asynchronously, i.e. the system
performs a rollout. However, this may not be desirable if, for example, the data
is received in a SELECT loop,
the database cursor is lost due to the rollout and the loop is terminated. To
prevent a rollout, you can use the addition HOLD . Then, the SAP process waits
until the data has been received and is thus available for use by other
users.

Note

The fields d , s and m which contain information about the outcome
of the call must be of type X with length 4.

Example

FORM CPIC_EXAMPLE.
TYPES: CONVERSATION_ID(8) TYPE C,
       RETURN_CODE        LIKE SY-SUBRC,
       C_INFO(4)          TYPE X.
DATA:  CONVID  TYPE CONVERSATION_ID,
       CPIC_RC TYPE RETURN_CODE,
       RECORD(80) TYPE C,
       DINFO      TYPE C_INFO,
       SINFO      TYPE C_INFO.
INCLUDE RSCPICDF.

COMMUNICATION ACCEPT ID CONVID
                     RETURNCODE  CPIC_RC.
IF CPIC_RC NE CM_OK.
   EXIT.
ENDIF.

COMMUNICATION RECEIVE ID         CONVID
                      BUFFER     RECORD
                      STATUSINFO SINFO
                      DATAINFO   DINFO
                      RETURNCODE CPIC_RC.
IF CPIC_RC NE CM_OK.
   EXIT.
ENDIF.
ENDFORM.

Variant 6

COMMUNICATION DEALLOCATE ID id.

Addition

As for variant 1

Effect

Severs connection and releases all resources.

Example

TYPES: CONVERSATION_ID(8) TYPE C,
     DESTINATION(8)     TYPE C,
     RETURN_CODE        LIKE SY-SUBRC,
     C_INFO(4)          TYPE X.
DATA:  CONVID  TYPE CONVERSATION_ID,
     CPIC_RC TYPE RETURN_CODE,
     DEST    TYPE DESTINATION VALUE 'C00'.

DATA:  RECORD(80) TYPE C,
     LENG       TYPE I VALUE 20.

INCLUDE RSCPICDF.

COMMUNICATION INIT DESTINATION DEST
                 ID          CONVID
                 RETURNCODE  CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: / 'COMMUNICATION INIT, RC = ', CPIC_RC.
 EXIT.
ENDIF.
COMMUNICATION ALLOCATE ID CONVID
                     RETURNCODE CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: / 'COMMUNICATION ALLOCATE, RC = ', CPIC_RC.
 EXIT.
ENDIF.
RECORD = 'The quick brown fox jumps over the lazy dog'.
COMMUNICATION SEND ID     CONVID
                 BUFFER RECORD
                 LENGTH LENG
                 RETURNCODE CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: / 'COMMUNICATION SEND, RC = ', CPIC_RC.
 EXIT.
ENDIF.
COMMUNICATION DEALLOCATE ID CONVID
                       RETURNCODE CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: / 'COMMUNICATION DEALLOCATE, RC = ', CPIC_RC.
 EXIT.
ENDIF.

Note

The above examples illustrate the basic functionality of the key
words. However, the example program can only have an external system as partner.
If the partner is an SAP System, the calling program must first logon to the SAP
System and receive an acknowledgement. Only then can you begin to transmit the
actual data. When logging on to an R2 System and an R3 System, the logon data
must be converted to EBCDIC . All user data should be converted according to the
partner system. This is in the concluding example of an R/3 – R/2 connection.

Example

PROGRAM ZCPICTST.
TYPES: CONVERSATION_ID(8) TYPE C,
     DESTINATION(8)     TYPE C,
     RETURN_CODE        LIKE SY-SUBRC,
     C_INFO(4)          TYPE X.

DATA:  BEGIN OF CONNECT_STRING,
       REQID(4) VALUE 'CONN',
       TYPE(4)  VALUE 'CPIC',
       MODE(4)  VALUE '1   ',
       MANDT(3) VALUE '000',
       NAME(12) VALUE 'CPICUSER',
       PASSW(8) VALUE 'CPIC',
       LANGU(1) VALUE 'D',
       KORRV(1),
       REPORT(8) VALUE 'ZCPICTST',
       FORM(30)  VALUE 'CPIC_EXAMPLE',
     END OF CONNECT_STRING.

DATA:  CONVID   TYPE CONVERSATION_ID,
     DEST     TYPE DESTINATION VALUE 'R2-SYST',
     CPIC_RC  TYPE RETURN_CODE,
     DINFO    TYPE C_INFO,
     SINFO    TYPE C_INFO.

DATA:  RECORD(80) TYPE C,
     LENG       TYPE I VALUE 20.
INCLUDE RSCPICDF.

COMMUNICATION INIT DESTINATION DEST
                 ID          CONVID
                 RETURNCODE  CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: / 'COMMUNICATION INIT, RC = ', CPIC_RC.
 EXIT.
ENDIF.
COMMUNICATION ALLOCATE ID CONVID
                     RETURNCODE CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: / 'COMMUNICATION ALLOCATE, RC = ', CPIC_RC.
 EXIT.
ENDIF.

* Convert logon data to EBCDIC
TRANSLATE CONNECT_STRING TO CODE PAGE '0100'.
COMMUNICATION SEND ID CONVID BUFFER CONNECT_STRING.
IF CPIC_RC NE CM_OK.
 WRITE: / 'COMMUNICATION ALLOCATE, RC = ', CPIC_RC.
 EXIT.
ENDIF.
* Receive acknowledgement of logon
COMMUNICATION RECEIVE ID      CONVID
                 BUFFER     RECORD
                 DATAINFO   DINFO
                 STATUSINFO SINFO
                 RETURNCODE CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: / 'COMMUNICATION RECEIVE, RC = ', CPIC_RC.
 EXIT.
ENDIF.
* Convert acknowledgement to ASCII
TRANSLATE RECORD FROM CODE PAGE '0100'.

* Now begin user-specific data exchange
RECORD = 'The quick brown fox jumps over the lazy dog'.

* Depending on the partner system, convert to another
* character set
TRANSLATE RECORD TO CODE PAGE '0100'.

COMMUNICATION SEND ID     CONVID
                 BUFFER RECORD
                 LENGTH LENG
                 RETURNCODE CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: / 'COMMUNICATION SEND, RC = ', CPIC_RC.
 EXIT.
ENDIF.
COMMUNICATION DEALLOCATE ID CONVID
                       RETURNCODE CPIC_RC.
IF CPIC_RC NE CM_OK.
 WRITE: / 'COMMUNICATION DEALLOCATE, RC = ', CPIC_RC.
 EXIT.
ENDIF.

PROGRAM ZCPICTST.
INCLUDE RSCPICDF.
* The receiving procedure in the relevant partner program follows
FORM CPIC_EXAMPLE.
TYPES: CONVERSATION_ID(8) TYPE C,
       RETURN_CODE        LIKE SY-SUBRC,
       C_INFO(4)          TYPE X.
DATA:  CONVID  TYPE CONVERSATION_ID,
       CPIC_RC TYPE RETURN_CODE,
       RECORD(80) TYPE C,
       DINFO      TYPE C_INFO,
       SINFO      TYPE C_INFO.

COMMUNICATION ACCEPT ID CONVID
                     RETURNCODE  CPIC_RC.
IF CPIC_RC NE CM_OK.
   EXIT.
ENDIF.
COMMUNICATION RECEIVE ID         CONVID
                      BUFFER     RECORD
                      STATUSINFO SINFO
                      DATAINFO   DINFO
                      RETURNCODE CPIC_RC.
IF CPIC_RC NE CM_OK AND CPIC_RC NE CM_DEALLOCATED_NORMAL.
   EXIT.
ENDIF.
ENDFORM.