Sockets Programming
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Michigan iSeries Technical
Education Conference
MQ Series
IBM’s Middleware
Solution
Presented by
Ryan Technology Resources
Michael Ryan
[email protected]
(C)opyright 2006
Michael Ryan
What is Middleware?
• Middleware is software that
manages several parts of a
connection between systems
• Physical and logical communications
• Data translation
• Error recovery
• Message sequencing
MQ Series
‘Proper name’ is Websphere MQ
Framework for communications
Multiple levels
Different operating systems
Different hardware platforms
Different communication protocols
Ubiquitous connectivity
Multiple Platforms
AIX
Compaq NSK
DOS
DYNIX/ptx
HP-UX
Linux
MacOS MVS/ESA
NUMA-Q
OpenVMS Alpha
OpenVMS VAX
OS/2
OS/390
OS/400
Sun Solaris
UNIX
Unisys 2200 Series
Unisys A Series
VM/ESA
VSE/ESA
Windows Java
Access
Programmatically accessed through
Application Programming Interfaces (API)
Same concept for each system
‘Store and Forward’
Not unlike SNADS
Guaranteed delivery
Asynchronous communication
Components
Four main components of MQ Series
Queue manager
Queues
Channels
Messages
Messages
The data being sent between applications
Has meaning to the application – no particular
meaning to MQ Series
Two parts – the application data and a message
descriptor
Application data is what the applications are sending
and receiving with each other
Message descriptor is something that is not seen by
the application programmer. It contains information
such as the from and to queue names, the priority,
levels of MQ Series, security information and so on
Queues
Message repository - sent to or received from
Not unlike data queues (*DTAQ)
Use APIs to access MQ Series data queues
Independent of the application
Characteristics
Put-enabled (messages can be placed on the queue)
Get enabled (messages may be retrieved from the
queue)
Queue depth
Queue size
Queue Manager
Responsible for queues
Every queue belongs to a queue manager,
whether the queue is local or remote
A local queue managed by a local queue manager –
a queue manager on the same system as a queue
A remote queue is manager by a remote queue
manager – a queue manager on a different system
A local application puts messages on a remote
queue (which is a local queue to the remote system)
and the remote application puts messages on a local
queue (which is remote to the local application)
Queue Manager
Local System
Managed by
remote system
queue manager
Remote Queue
Remote System
Local Queue
Managed by
local system
queue manager
Local Queue
Remote Queue
Channels
Link between the actual communications and
the MQ Series queue managers
Type of communications (TCP/IP or SNA)
Two types – message channels and client channels
• A message channel is used for server-to-server
communication
• Unidirectional
• Two channels - a sending channel and a receiving channel
• A client channel connects a client to a server
• Bi-directional
• Queues exist on the server – there are no client queues
MQ Configuration
Use RSTLICPGM
Developed in Hurlsley, supported from Raleigh
(Software Group)
Loads
5733-A38
QMQM library
Objects in the IFS
User profiles QMQM and QMQMADM
Read the instructions…
MQ Configuration - WRKMQM
MQ Configuration - CRTMQM
MQ Configuration -CRTMQMCHL
MQ Configuration -CRTMQMQ
MQ Programming
The programming model for MQ Series
applications is similar to any communications
program
One system (usually the client) sends a message (a
request for services) to the other system (usually the
server)
The server then replies with the information desired
by the client. This process continues until the client
or the server desire to end the communication.
MQ Programming
Contrast MQ Series with sockets
programming
Amount of code needed for an MQ Series
program is much less than a socket program
• Don’t need to code for ‘low-level’ handshaking
• Low-level error recovery is performed by MQ
Don’t need to ‘connect’ or ‘accept’
• Just read and write to queues
MQ Programming - APIs
Application Programming Interface
• Relatively few APIs
• Most commonly used
MQCONN – Connect to a Queue Manager
MQDISC – Disconnect from a Queue Manager
MQOPEN – Open an MQ object (Queue)
MQCLOSE – Close an MQ object (Queue)
MQPUT – Put a message to an MQ Queue
MQGET – Get a message from an MQ Queue
MQ Programming - APIs
Other APIs are available but usually not needed
MQINQ – Inquire about an MQ object (Queue,
Queue Manager, Channel…)
MQSET – Set some of the attributes of a Queue
MQBEGIN – Begin a Unit of Work in a Commitment
Control environment
MQCMIT – Commit a Unit of Work in a Commitment
Control environment
MQBACK - Rollback a Unit of Work in a Commitment
Control environment
MQ Programming - Model
The general flow of events in an MQ Series
application program is:
1. Connect to a queue manager with MQCONN
2. Open the queues needed for communication with
MQOPEN
3. Use MQPUT and MQGET to send and receive
messages
4. Close the opened queues with MQCLOSE
5. Disconnect from the queue manager with MQDISC
MQ Programming - RPG
MQ Series applications usually follow the model
Using MQ Series in an RPG application is
simple
Procedures called by the APIs are in service
program QMQM/LIBMQM
Ensure this service program is bound by reference
with your RPG program
The data structures and prototype definitions
can be found in library QMQM
MQ Programming - RPG
Here’s an example of /INCLUDEs I use in my
MQ Series programs:
* MQI Named Constants
/COPY QMQM/QRPGLESRC,CMQG
* Object Descriptor
D MQOD
DS
/COPY QMQM/QRPGLESRC,CMQODG
* Message Descriptor
D MQMD
DS
/COPY QMQM/QRPGLESRC,CMQMDG
* Get Message Options
D MQGMO
DS
/COPY QMQM/QRPGLESRC,CMQGMOG
* Put message options
D MQPMO
DS
/COPY QMQM/QRPGLESRC,CMQPMOG
MQ Programming - RPG
These includes will copy in
Named constants
Object descriptor information
Message descriptor information
Put and get option information
Review these include files to identify the
field names and prototyped names you
will use in your program
MQ Programming - RPG
Example of connecting to a queue manager:
*
C
C
C
C
C
*
C
Connect to MQ Series queue manager.
CallP
MQConn(QMName :
HConn :
OCode :
Reason)
If
OCode = CCFail
Error occurred...
EndIf
MQ Programming - RPG
QMName contains the name of the queue manager
HConn is returned from the API call
OCode and Reason are returned by the API call and
identify if an error occurred
Contains the ‘handle’ that will be used in later calls
The handle identifies the specific queue manager and is used
internally by MQ Series
Note: I check OCode to see if it is equal to the named constant
CCFail – if so, an error occurred
Appropriate error recovery code goes here
This call completes the first step in the MQ Series
application flow – connecting to the queue manager
MQ Programming - RPG
*
C
C
C
C
C
C
C
C
C
*
C
Example of opening a queue:
Options are input-as-queue-def and fail-if-quiescing
Eval
Opts = OOInpq + OOFIQ
Eval
ODon = ReplyQue
CallP
MQOpen(HConn
:
MQOD
:
Opts
:
HInObj :
OCode
:
Reason)
If
Reason <> RCNone
Error occurred...
EndIf
MQ Programming - RPG
Variable Opts is set to special named constant
values OOInpq and OOFIQ
Variable ODon has the value of ReplyQue
Open the queue as input
Fail if quiescing
Contains the name of a queue
Association already established between the queue
manager and the queue during creation
HConn is the queue manager handle
Obtained from the MQConn call
MQ Programming - RPG
MQOD variable specified in the MQOpen call is
a data structure.
HinObj is returned from the API call and
contains the handle for the opened queue
ODon is one of the many subfields in the data
structure
Used for puts and gets
OCode and Reason are returned from the API
call and indicate an error
If Reason does not contain the value in named
constant RCNone, an error has occurred
MQ Programming - RPG
An example of MQPut:
C
C
C
C
C
C
C
C
C
C
C
C
Eval
Eval
Eval
CallP
*
C
MQGet follows the same pattern
If
Error occurred...
EndIf
MdFmt = FmStr
MDRQ = ReplyQue
MDRM = QMName
MQPut(HConn
:
HOutObj :
MQMd
:
MQPmo
:
BufLen :
BufPtr :
CCode
:
Reason)
Reason <> RCNone
MQ Programming - RPG
Note the MQ* variables
These are subfields in data structure MQMD and
MQPMO
Set these variables to specific values that are
determined by the needs of the application
BufLen contains the length of the buffer of
information that we are sending
BufPtr is a variable of type pointer that contains the
address of the buffer of information
As before, we interrogate the Reason to determine if
an error has occurred
MQ Programming - RPG
C
C
C
C
C
C
C
C
C
*
*
C
C
*
C
C
*
C
An example of MQGet:
CallP
MQGet(HConn :
HInObj :
MQMd
:
MQGmo :
BufLen :
BufPtr :
MsgLen :
CCode :
Reason)
Note: Reason should be 0 (RCNone). If return code = 2033 (RC2033),
no messages are available.
If
Reason <> RCNone
If
Reason <> RC2033
Error occurred...
EndIf
Else
process the data…
EndIf
MQ Programming - RPG
Note the MQ* variables
Contain the specific values that are used by the MQGet call to
control its operation and are subfields in the MQMD and
MQGMO data structures
BufLen is the length of the receive buffer
BufPtr is a pointer to the buffer
MsgLen is the number of bytes returned from the MQGet call
Lookingfor a specific Reason code and not signaling an error if
it’s encountered
• A 2033 Reason code (in named constant RC2033) indicates that
an MQGet was performed and no data was available to be read
• This is certainly possible – the other system may have no data to
send at that time.
MQ Programming - RPG
An example of MQClose:
*
C
C
C
C
C
C
C
*
C
Close input MQ Series connection.
Eval
Opts = CONone
CallP
MQClose(HConn :
HInObj :
Opts
:
CCode :
Reason)
If
Reason <> RCNone
Error occurred...
EndIf
MQ Programming - RPG
Queue manager handle
HConn – specified in the MQConn call
Queue handle
HinObj – specified in the MQOpen call
An options field
Check the returned Reason to see if an
error occurred
MQ Programming - RPG
An example of MQDisc:
*
C
C
C
*
C
*
C
Disconnect from MQ Series Queue Manager.
CallP
MQDisc(HConn :
OCode :
Reason)
Report reason and stop if failed.
If
OCode = CCFail
Error occurred...
EndIf
MQ Programming - RPG
Specify the handle from the MQConn call
Check for an error
MQ Programming - C
An MQOpen Example in C:
O_options = MQOO_INPUT_AS_Q_DEF /* open queue for input */
+ MQOO_FAIL_IF_QUIESCING;
/* but not if stopping */
MQOPEN(Hcon,
od,
O_options,
&HInobj,
&InOpenCode,
&Reason);
/*
/*
/*
/*
/*
/*
connection handle
*/
object descriptor for queue */
open options
*/
object handle
*/
completion code
*/
reason code
*/
MQ Series
MQ Series (or the WebSphere MQ Family)
Very strong and robust solution to middleware
problems
Reliable
Flexible
Easy to configure
Easy to program
Excellent choice for connectivity and system
integration issues
Getting More Information
• IBM Websphere MQ Site
• http://www-306.ibm.com/software/integration/wmq/
• AS/400 Red Books
• MQSeries Version 5.1 Administration and Programming
Examples
• http://www.redbooks.ibm.com/redbooks/SG245849.html
• Great forum for MQ stuff
• http://www.mqseries.net/