This chapter is for RPC programmers. It explains:
• What components a distributed application contains
• How to use RPC to develop a distributed application, step by step
Table 6-1 lists the components of a distributed application.
Table 6-1 Application Components
|
Component |
Description |
|
Main program (client) |
An ordinary main program that calls a remote procedure as if local |
|
Network interface |
Client and server stubs, header files, XDR routines for input arguments and results |
|
Server procedure |
Carries out the client's request (at least one is required) |
These components may be written in any high-level language. The RPC Run-Time Library (RTL) routines are written in the C language.
The following steps summarize what you need to do to build a distributed application:
1 Design the application.
2 Write an RPC interface definition. Compile it using RPCGEN, then edit the output files as necessary. (This step is optional. An RPC interface definition is not required. If you do not write one, proceed to step 3.)
3 Write any necessary code that RPCGEN did not generate.
4 Compile the RPCGEN output files, server procedures, and main program using the appropriate language compiler(s). RPCGEN output files must be compiled using HP C.
5 Link the object code, making sure you link in the RPC RTL.
6 Start the Port Mapper on the server host.
7 Execute the client and server programs.
You must write a main (client) program and at least one server procedure. The network interface, however, may be hand-written or created by RPCGEN. The network interface files contain client and server stubs, header files, and XDR routines. You may edit any files that RPCGEN creates.
When deciding whether to write the network interface yourself, consider these factors:
|
Is execution time critical? |
Your hand-written code may execute faster than code that RPCGEN creates. |
|
Which RPC interface layer do you want to use? |
RPCGEN permits you to use only the highest layer interface. If you want to use the lower layers, you must write original code. The RPC Fundamentals, Chapter 6, describes the characteristics of each RPC interface layer. |
|
Which transport protocol do you want to use? |
You may write your own XDR programs, but it is usually best to let RPCGEN handle these.
An interface definition is a program the RPCGEN compiler accepts as input. The RPCGEN Compiler, Chapter 8, explains exactly what interface definitions must contain.
Interface definitions are optional. If you write the all of the network interface code yourself, you do not need an interface definition.
You must write an interface definition if you want RPCGEN to generate network interface code.
After compiling the interface definition, edit the output file(s).
If you are not writing an interface definition, skip this step and proceed to step3.
Write any necessary code that RPCGEN did not create for you. Table 6-2 lists the texts you may use as references.
|
Reference |
Purpose |
|
RFC 1057 |
Defines the RPC language. Use for writing interface definitions. |
|
RFC 1014 |
Defines the XDR language. Use for writing XDR filter routines. |
|
The RPC RTL Client Routines chapter and those that follow |
Defines each routine in the RPC RTL. Use for writing stub procedures and XDR filter routines. |
Compile the RPCGEN output files, server procedures, and main program separately.
HP C (VAX and Alpha):
$ CC /STANDARD=RELAXED /WARNING=DISABLE=(IMPLICITFUNC) filename.C
Link the object code files. Make sure you link in the RPC RTL. Use the following command.
HP C (VAX and Alpha):
$ LINK filenames, SYS$INPUT /OPTIONS
TCPIPC$RPCXDR_SHR /SHARE
SYS$SHARE:DECC$SHR /SHARE
Ctrl/Z
After entering the command, press Ctrl/Z.
To avoid repetitive data entry, you may create an OpenVMS command procedure to execute these commands.
The Port Mapper must be running on the server host. If it is not running, use the MULTINET CONFIGURE/SERVER command to start it. If you want to generate your own screen shot, you can use CRASH. Then all you have to do is change the user-entered items to bold, and change the
v5.1 ( 42) to v5.1 (nnn) in the banner line.
Perform these steps:
1 Run the server program interactively to debug it, or using the /DETACHED qualifier. Refer to HP’s documentation for details.
2 Run the client main program.
You can:
• Request a listing of all programs registered with a Port Mapper.
To request a listing of all programs that are registered with the Port Mapper, enter the MULTINET SHOW /RPC_PORTMAP command in the following format at the DCL prompt:
$ MULTINET SHOW /RPC_PORTMAP
If you add /REMOTE_HOST=hostname to this command:
$ MULTINET SHOW /RPC_PORTMAP /REMOTE_HOST=[host-name]
Specify the domain name of the host on which the Port Mapper resides. If you omit this parameter, RPC uses the name of the local host. Example 7-1 shows an example.
Example 7-1 Sample RPC Information Output
$ MULTINET SHOW/RPC_PORTMAP
MultiNet registered RPC programs:
Program Version Protocol Port
------- ------- -------- ----
NLOCKMGR 3 TCP 2049
NLOCKMGR 1 TCP 2049
NLOCKMGR 3 UDP 2049
NLOCKMGR 1 UDP 2049
NFS 2 TCP 2049
NFS 2 UDP 2049
MOUNT 1 TCP 1024
MOUNT 1 UDP 1028
STATUS 1 TCP 1024
STATUS 1 UDP 1024
