Hello world RPC

What is RPC?
         RPC stand for Remote procedure call.

We will see how to run an RPC program in Ubuntu.

Open the Terminal and type     rpcinfo
                      If you get error you must type the following command
                            Note:- You must connect to the internet before type he following command.
                     
                                      sudo apt-get install rpcbind
                                      To verify the installation retype rpcinfo
                       If you got the .following details.
                         

                           Now you can proceed.

What is our program do.

•     Simply it is send the First and second initials in your name.
•     Then server will print the both Initials.
•     After that server replies how many messages server handle so far (with this message).
•     Client will print it.

Now open text Editor and add the following code to a blank file.

struct messages{
char firstinitial;
char secondinitial;
};


program HELLO {
version HELLO_1{
int MY_FUNCTION(messages)=1;
}=1;
}=0x2fffffff;

We can use only one parameter for a function. So when we want to send 2 parameters simply we do is make structure (Class in java )which has number of parameters. So I need to send 2 parameters. Then I made a structure with 2 character parameters.

program HELLO 
this means the programs name. It must be capital.

version HELLO_1
This must be a capital.

int MY_FUNCTION(messages)=1;

This is the method we going to call remotely.
       int                             - return type
       MY_FUNCTION    - function name
       messages                  - type of the parameter
       1                               - number of the function. (I will give this as method number 1)

=1;
Version of the program

=0x2fffffff;
  Program number.


Then save it as hello.x

by using Terminal go to the folder where the hello.x is located.
Then type following command

            rpcgen -a -C hello.x

You can see some files were created in the folder where the hello.x is located.

Now open the hello_client.c file in that folder.

It must be something like this.

/*

 * This is sample code generated by rpcgen.

 * These are only templates and you can use them

 * as a guideline for developing your own functions.

 */

#include "hello.h"

void

hello_1(char *host)

{

CLIENT *clnt;

int  *result_1;

messages  my_function_1_arg;

#ifndef DEBUG

clnt = clnt_create (host, HELLO, HELLO_1, "udp");

if (clnt == NULL) {

clnt_pcreateerror (host);

exit (1);

}

#endif /* DEBUG */

result_1 = my_function_1(&my_function_1_arg, clnt);

if (result_1 == (int *) NULL) {

clnt_perror (clnt, "call failed");

}

#ifndef DEBUG

clnt_destroy (clnt);

#endif /* DEBUG */

}

int

main (int argc, char *argv[])

{

char *host;

if (argc < 2) {

printf ("usage: %s server_host\n", argv[0]);

exit (1);

}

host = argv[1];

hello_1 (host);

exit (0);

}

Explain:-

  my_function_1_arg -- Client must put data to here for send to server.

  *result_1  -- Servers reply will catch by this variable.

result_1 = my_function_1(&my_function_1_arg, clnt);   --- Where the function calls and get the reply

Now add the following sections.

        my_function_1_arg.firstinitial='L';

my_function_1_arg.secondinitial='J';

            This section must add before the  very first line of      #ifndef DEBUG line.    

                    Note:- you can add this line any where you want befor calling my_function1

       printf("You connect with server for %d time",result_1[0]);

             This section must add before the clnt_destroy (clnt); line.

                        Note:- you can add this line any where you want after calling my_function1

Now save the file.

AFTER EDIT CLIENT CODE LOOKS LIKE THIS

/*
 * This is sample code generated by rpcgen.
 * These are only templates and you can use them
 * as a guideline for developing your own functions.
 */

#include "hello.h"


void
hello_1(char *host)
{
CLIENT *clnt;
int  *result_1;
messages  my_function_1_arg;

my_function_1_arg.firstinitial='L';
my_function_1_arg.secondinitial='J';

#ifndef DEBUG
clnt = clnt_create (host, HELLO, HELLO_1, "udp");
if (clnt == NULL) {
clnt_pcreateerror (host);
exit (1);
}
#endif /* DEBUG */

result_1 = my_function_1(&my_function_1_arg, clnt);
if (result_1 == (int *) NULL) {
clnt_perror (clnt, "call failed");
}
#ifndef DEBUG
printf("You connect with server for %d time",result_1[0]);
clnt_destroy (clnt);
#endif /* DEBUG */
}


int
main (int argc, char *argv[])
{
char *host;

if (argc < 2) {
printf ("usage: %s server_host\n", argv[0]);
exit (1);
}
host = argv[1];
hello_1 (host);
exit (0);
}



---

---

Now open the hello_server.c file.

It must look like this.

/*

 * This is sample code generated by rpcgen.

 * These are only templates and you can use them

 * as a guideline for developing your own functions.

 */

#include "hello.h"

int calls=0;

int *

my_function_1_svc(messages *argp, struct svc_req *rqstp)

{

static int  result;

calls++;

/*

* insert server code here

*/

printf("Full initials are :- %c and %c \n",argp->firstinitial,argp->secondinitial);

result=calls;

return &result;

}

Edit it on following way.


/*
 * This is sample code generated by rpcgen.
 * These are only templates and you can use them
 * as a guideline for developing your own functions.
 */

#include "hello.h"


void
hello_1(char *host)
{
CLIENT *clnt;
int  *result_1;
messages  my_function_1_arg;

my_function_1_arg.firstinitial='L';
my_function_1_arg.secondinitial='J';

#ifndef DEBUG
clnt = clnt_create (host, HELLO, HELLO_1, "udp");
if (clnt == NULL) {
clnt_pcreateerror (host);
exit (1);
}
#endif /* DEBUG */

result_1 = my_function_1(&my_function_1_arg, clnt);
if (result_1 == (int *) NULL) {
clnt_perror (clnt, "call failed");
}
#ifndef DEBUG
printf("You connect with server for %d time",result_1[0]);
clnt_destroy (clnt);
#endif /* DEBUG */
}


int
main (int argc, char *argv[])
{
char *host;

if (argc < 2) {
printf ("usage: %s server_host\n", argv[0]);
exit (1);
}
host = argv[1];
hello_1 (host);
exit (0);
}


Now save it.

Then in terminal enter the following command.

             make -f Makefile.hello 

Then new files will create in the folder.

Then type sudo ./hello_server .

Now open a new terminal and go to the folder where the hello.x is located.

Now type sudo ./hello_client localhost .

local host means server's address.

You can see the following data in both terminals as a result

Do the sudo ./hello_client localhost      again and see the results.