Chapter 2 Building and Running MQ C Clients

This chapter provides information about building MQ C client applications and making sure these programs have adequate run-time support. It also lists the sample MQ C Client programs that are included with the MQ installation, and explains how you should run them

Getting Ready

MQ provides several sample MQ C-client applications that illustrate how to send and receive messages. These sample applications are installed in the ...demo\C directory. Before you run these applications, read through the next two sections to make sure that you understand the general procedure and requirements for building and running MQ C-Client programs.

Building Programs

This section explains how you build MQ programs from C source files.You should already be familiar with writing and compiling C applications.

The MQ C client includes the header files (mqcrt.h), the C client runtime shared library mqcrt, and its direct dependency libraries. When writing an MQ C client application, you should include the header files and link to the runtime library mqcrt. Note that the MQ C-API runtime library is a 32-bit library. For each platform, Table 2-1 lists the installed location of the header files and the supporting runtime library.

Table 2-1 Locations of C-API Libraries and Header Files
Platform	Library	Header File
Solaris	/opt/SUNWimq/lib	/opt/SUNWimq/include
Linux	/opt/imq/lib	/opt/imq/include
Windows	IMQ_HOME\lib	IMQ_HOME\include

You should use the appropriate compiler for your platform, as described in the MQ Installation Guide.

When compiling an MQ C client application, you need to specify the preprocessor definition for supporting MQ fixed-size integer types. The preprocessor definition for each platform is shown in Table 2-2.

Table 2-2 Preprocessor Definitions for Supporting MQ Fixed-Size Integer Types
Platform	Definition
Solaris	SOLARIS
Linux	LINUX
Windows	WIN32

When building an MQ C client application, you should be aware that the MQ C runtime library is a multi-threaded library and requires C++ runtime library support:

On Solaris, this support is provided by the Sun WorkShop 6 libCrun C++ runtime library.

On LINUX, this support is provided by the gcc/g++ libstdc++ runtime library.

On Windows, this support is provided by Microsoft Windows Visual C++ runtime library msvcrt.

Providing Runtime Support

To run an MQ C-client application, you need to make sure that the application can find the mqcrt shared library. Please consult the documentation for your compiler to determine the best way to do this.

You also need to make sure that the appropriate C++ runtime support library, as described in "Building Programs" is available.

On Windows you also need to make sure that your application can find the dependent libraries NSPR and NSS that are shipped with MQ. These may be different from the NSPR and NSS libraries that are installed on your system to support the Netscape browser and the Application Server. The mqcrt shared library depends directly on the NSPR and NSS versions installed with MQ. If a different version of the libraries are loaded at runtime, you may get a runtime error specifying that the libraries being used are incompatible.

Working With the Sample C-Client Programs

This section describes the sample C-Client programs that are installed with MQ and explains how you should build them and run them.

Building the Sample Programs

The following commands are meant to illustrate the process of building and linking the sample application Producer.c on the Solaris, Linux, and Windows platforms. The commands include the preprocessor definitions needed to support fixed-size integer types. For options used to support multithreading, please consult documentation for your compiler.

To Compile and Link on Solaris

CC -compat=5 -mt -DSOLARIS -I/opt/SUNWimq/include -o Producer \
-L/opt/SUNWimq/lib -lmqcrt Producer.c

To Compile and Link on Linux

g++ -DLINUX -D REENTRANT -I/opt/imq/include -o Producer \
-L/opt/imq/lib -lmqcrt Producer.c

To Compile on Windows

To Link on Windows

Running the Sample Programs

Sample C client program files are installed in the ...demo\C directory. These include the following:

Producer.c and Consumer .c, which illustrate how you send a message and receive it synchronously.

ProducerAsyncConsumer.c, which illustrates how you send a message and receive it asynchronously.

RequestReply.c, which illustrates how you send and respond to a message that specifies a reply-to destination.

The sample programs expect you to specify a destination as a command-line argument. You can either create one or more physical destinations on the broker by using the administration utility imqcmd before running the sample programs, or you can use the broker’s auto-creation feature by specifying any destination name on the command line used to start the program.

Before you run any sample programs, you should start the broker. You can display output describing the command-line options for each program by starting the program with the -help option.

The …demo\C directory also includes a README file that explains how you should run these samples. For example, the following command, runs the program Producer. It specifies that the program should connect to the broker running on the host MyHost and port 8585, and that it should send a message to the destination My Topic: