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RPC Programming quick start
Netbula RPCGen
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RPC Programming Quick Start

If you are not familiar with ONC RPC, then the book "Power Porgramming RPC" from O'Reilly is a useful guide. Also, there is extensive online documentation for programming ONC RPC from DEC.

The following is a sample program included under the samples/MyMgSvc/ folder of the ONC RPC SDK.

1) Define the RPC Interface in a .x file.


 struct aTypeStruct {
    int i;
    double d;
 };
 typedef struct aTypeStruct aType;
 program MyRPCService {
      version ThisVersion {
              aType function_foo(int) = 1;
              int    function_bar(aType) =2;
      }=1;
 }=34567;


Here, we defined an RPC interface with program number 34567, and two procedures function_foo and function_bar, save it to a file named MyRPCService.x .

2) Use RPCGen to compile the .x file


% rpcgen MyRPCService.x


type the command "rpcgen MyRPCService.x" at the command prompt. This will produce the following files

  • MyRPCService.h --- the common header file for the RPC, read the generated comments.
  • MyRPCService_xdr.c --- the XDR routine for struct aType. This file will be used by both the client and the server.
  • MyRPCService_cln.c --- The generated client stub. An RPC client application calls the functions defined in this file.
  • MyRPCService_svc.c --- The generated server stub.
  • MyRPCService_imp.tmp.c --- The server implmentation template, you copy this file and fill in the server implementation.
  • MyRPCService.hpp ---- The C++ class for the client
  • MyRPCService.mak ---- Makefile, you need to edit this

3) Code the server implementation

The MyRPCService.h file included the declarations for two functions function_foo_svc() and function_bar_svc(), the RPC server programmer must implement these two functions to do the real work. Let's assume the implemtation is coded in the file MyRPCService_imp.c .

Rpcgen generates a server implementation template file, you can copy it over and fill in the details.

4) Build and run the server

Compile the MyRPCService_xdr.c, MyRPCService_svc.c and MyRPCService_imp.c files. Make sure the include/ directory of the Netbula ONC RPC SDK is in the include path. Link with the pwrpc32.lib import library to build an executable. When you run the built RPC server/client, make sure pwrpc32.dll can be found by the application.

The ONC RPC SDK contains a makefile template which can be easily modified to use for this sample application.

To run the RPC server, first start the portmapper (pmapsvc or portmap.exe), then start MyRPCService server we just build.

5) Write a client

The client code looks like this:


 int i;
 aType a, *ap;
 CLIENT * cl = 
        clnt_create("server_host_name", program_number, version_number, "tcp");
 ap = function_foo_1(&i, cl);
 i = function_bar_1(&a, cl);
 

RPCGEN also generates C++ code for the client. The client calling code is listed in cxx_client_main.cpp.
			
#include <stdio.h>
#include <rpc/rpc.h>

/* we must define RPC_CLIENT in the client */
#define RPC_CLIENT

#include "MyRPCService.hpp"

int main(int argc, char*argv[])
{
	
	int i=100, i2=0;
	aType atype;
	int result_code=0;

	CMyRPCService client("localhost", "udp");
	
	CLIENT* cl = client.getHandle();
	
  //check for create error
if (cl == NULL) { client.pcreateerror(argv[1]); exit (1); } result_code = client.function_foo_1(&i, &atype); if(result_code ==0) { printf("Got reply {%d, %f}\n", atype.i, atype.d); }else { client.perror("MyRPC"); } if(0==(result_code = client.function_bar_1(&atype, &i2))) { printf ("Got reply %d\n", i2); }else { client.perror("MyRPC"); } xdr_free((xdrproc_t)xdr_aType, (char*) &atype); client.destroy(); return 0; }

Netbula RPCGen Usage

The following is modified from rpcgen(1) man page on UNIX systems.


NAME

rpcgen - an RPC protocol compiler

USAGE
  1. rpcgen infile
  2. rpcgen -c|-h|-l|-m [-o outfile] infile
  3. rpcgen -s transport [-o outfile] infile

DESCRIPTION

rpcgen is a compiler that generates C source code from a protocol specification file (normally with .x suffix). When run without additional options flags, rpcgen produces the following C files from a input file named proto.x

  • proto.h
    Header file for data types and function prototypes.

  • proto_xdr.c
    XDR routines to encode/decode arguments and return values, used by both the client and the server.

  • proto_svc.c
    Server side stub. This contains mainly the code to start and register the server and the dispatch routine that receives client call requests and dispatch the calls to the server implementation functions.

  • proto_clnt.c
    Client side stub.

The C-preprocessor, CPP, is used by rpcgen to preprocess the input file. Therefore, rpcgen does not interprets the .x file directly, instead it operates on the output from CPP. rpcgen does multiple passes to generate each type of the files listed above, during each pass, it defines a different CPP symbol:

  • RPC_HDR defined when compiling into header files
  • RPC_XDR defined when compiling into XDR routines
  • RPC_SVC defined when compiling into server-side stubs
  • RPC_CLNT defined when compiling into client-side stubs

For instance, to produce the header file proto.h from proto.x, rpcgen goes through the following steps

  1. CPP -DRPC_HDR USER_CPP_FLAGS proto.x > tmpfile
  2. compile tmpfile into proto.h
  3. remove tmpfile
Netbula RPCGen for Win32 uses CL.EXE in MS Visual C++ as the default C-preprocessor (with flags /C /EP /nologo). The CL.EXE must be in the search path, or rpcgen will spit out a "preprocessing failed" error. VC++ come with script named vcvars32.bat which does the proper environment setting.

You can let rpcgen use a different CPP by setting two environment variables, RPCGEN_CPP and RPCGEN_CPP_FLAG, for the CPP program and associated flags, respectively.

Rpcgen does a little preprocessing of its own. Any line beginning with `%' is passed directly into the output file, uninterpreted by rpcgen.

You can customize some of your XDR routines by leaving those data types undefined. For every data type that is undefined, rpcgen will assume that there exists a routine with the name xdr_ prepended to the name of the undefined type.

OPTIONS

Flag

Argument

Description

-c none Compile into XDR routines.
-h none Compile into C data-definitions (a header file)
-l none Compile into client-side stubs.
-m none Compile into server-side stubs, but do not generate the "main" function. This option is useful for doing callback-routines and for people who need to write their own "main" function to do initialization.
-o output filename Specify the name of the output file. If none is specified, standard output is used (-c, -h, -l and -s modes only).
-s transport name
(udp or tcp)
Compile into server-side stubs, using the the given transport. The supported transports are udp and tcp. This option may be invoked more than once so as to compile a server that serves multiple transports. When this option is not given, rpcgen generates a server that listens on both the UDP and the TCP transport.

 

Portmapper service (Windows NT/2K/XP only)

When an RPC server starts up, it registers its program number and port with the Portmapper on its local machine. Before a client calls an RPC, it must contact the portmapper running on the server machine to find out the port number of the RPC server.

To install the portmap service, run from command line

> pmapsvc -i

To uninstall, run from command line 

> pmapsvc -u

To see the status,

> pmapsvc -v


To get help, run pmapsvc -h

To start the service, go to control panel, open the icon services, find the PowerRPC Portmapper and start it. 

 



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