LEARN BIOMETRIC

In this manual we go simulate the proccess the one system of biometric

• The first step will be to create a simple system client-server that communicate with the protocol XML-RPC.

• The second step will be to create a system client-server that simulate the Manage all processes of a system biometric with the protocol of communication XML-RPC.

First Module: System client-server that communicate with the protocol XML-RPC.

1. Install dependencies to work with XML-RPC

We go working with the linux distrubution Canaima that is a derivate of Debian Jessie.

1.1 Install Dependecies to Client

• Client common-libs:

Execute:

$ sudo apt install libusb-0.1-4 libusb-1.0-0 udev fxload

Client interface:

Execute:

$ sudo apt install libusb-0.1-4 libusb-1.0-0 udev fxload libjpeg62-turbo libxmlrpc-c++8 libxmlrpc-core-c3 libcurl3 libcurl3-gnutls libc6 openssl curl ca-certificates zenity

1.2 Install Dependencies to Server

Execute:

$ sudo apt install libxmlrpc-c++8-dev libxmlrpc-core-c3 libxmlrpc-core-c3-dev libcurl3-gnutls libc6 openssl apache2 apache2-mpm-prefork cron curl libcurl4-gnutls-dev g++ libjpeg-dev libcrypto++-dev libssl-dev libpqxx-dev

And active the mod cgi

$ a2enmod cgi

and restart apache

$ sudo service apache2 restart

2. Create the client

2.1 Create a directory to work:

$ mkdir client && cd client

2.2 Create a Header file the name client.h

This file contains all libraries of C++ that we need to work

With the following content:

#ifndef _Client_H_
#define _Client_H_

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fstream>
#include <XmlRpcCpp.h>
#include <iostream>
#include <algorithm>

#define NAME       "XML-RPC Guide C++ Client"
#define VERSION    "0.1"

#endif

2.3 Create the logic of the client

Create a file client.cpp with the following content:

#include "client.h"

using namespace std;

string url = "";
   
string archivo_config(string config_url_service)
{
	string url = "";
	string line;
	ifstream myfile( config_url_service.c_str() );
	if (myfile)
	{
		while (getline( myfile, line ))
		{
			line.erase(std::remove(line.begin(), line.end(), ' '), line.end());
			if (strcmp(line.c_str(), "") != 0)
			{
                printf("\nArchivo leído\n");
				url = line;
			}
		}
		myfile.close();
	}

	if(strcmp(url.c_str(), "") == 0)
	{
		ifstream myfile_default( "config/default" );
		if (myfile_default)
		{
			while (getline( myfile_default, line ))
			{
				line.erase(std::remove(line.begin(), line.end(), ' '), line.end());
				if (strcmp(line.c_str(), "") != 0)
				{
                    printf("\nArchivo leído default");
					url = line;
				}
			}
			myfile.close();
		}
	}

    printf("\nurl %s\n",url.c_str());
	return url;
}

int sumAndDifferen(int opp_1,int opp_2, double opp_3){

	XmlRpcClient::Initialize(NAME, VERSION);

    try {
        XmlRpcValue param_array = XmlRpcValue::makeArray();
        
        param_array.arrayAppendItem(XmlRpcValue::makeInt(opp_1));
        param_array.arrayAppendItem(XmlRpcValue::makeInt(opp_2));
        param_array.arrayAppendItem(XmlRpcValue::makeDouble(opp_3));
        
        string SERVER_URL = url.c_str();
		XmlRpcClient server (SERVER_URL);
        
        XmlRpcValue result = server.call("sample.sumAndDifferen", param_array);
        
        XmlRpcValue::int32 sum = result.structGetValue("sum").getInt();
        XmlRpcValue::int32 difference = result.structGetValue("difference").getInt();
        double doble = result.structGetValue("doble").getDouble();
        
        XmlRpcClient::Terminate();
        
        cout << "Sum " << sum << " difference " << difference << " doble " << doble << endl;
        
    } catch (XmlRpcFault& fault) {
		cerr << ": XML-RPC fault #" << fault.getFaultCode() << ": " << fault.getFaultString() << endl;
        XmlRpcClient::Terminate();
        return 0;
	}
}
  
int msj(string sms){

	XmlRpcClient::Initialize(NAME, VERSION);

    try {

        XmlRpcValue param_array = XmlRpcValue::makeArray();
        
        param_array.arrayAppendItem(XmlRpcValue::makeString(sms));
        
        string SERVER_URL = url.c_str();
		XmlRpcClient server (SERVER_URL);
        
        XmlRpcValue result = server.call("sample.msj", param_array);
        
        string message = result.structGetValue("message").getString().c_str();
        
        XmlRpcClient::Terminate();
        
        cout << "message " << message.c_str() << endl;
        
    } catch (XmlRpcFault& fault) {
		cerr << ": XML-RPC fault #" << fault.getFaultCode() << ": " << fault.getFaultString() << endl;
        XmlRpcClient::Terminate();
        return 0;
	}
		
}

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

	int option = atof(argv[1]);
    int opp_1 = atoi(argv[2]);
    int opp_2 = atoi(argv[3]);
    double opp_3 = atof(argv[4]);
    
    string sms = "LearnBiometric";

	string config = "config/config";
	url = archivo_config(config);

    switch (option) {

		case 1:
			sumAndDifferen(opp_1, opp_2, opp_3);
		break;

		case 2:
			msj(sms);
		break;

		default:
		  cout<<"Error, bad input, quitting\n";
		break;
	
	}

}

Now I will explain step by step the copied code

#include "client.h"

In this line include all libraries that we need to work, that are in the file that we created before

string archivo_config(string config_url_service)

archivo_config is a function receive a string as parameter

This function does two things:

• Verify that rute the file pass for parameter exist.
• Return in a variable the content the file.

Now we will create this file:

• Create a directory config

$ mkdir config 

• Create a file config with the following content:

http://localhost/cgi-bin/server_pruebas/server.cgi

That file content the url the server, to which we will do petitions

In this case the url is local.

• Create a file default with the following content:

http://localhost/cgi-bin/server.cgi

The same that the file config.

We continue with the explanation of the code

void sumAndDifferen(int opp_1,int opp_2, double opp_3)

• sumAndDifferen is a function that recieve 3 parameters, 2 int and 1 double

XmlRpcClient::Initialize(NAME, VERSION);

With this sentence initialize a client

try {
    XmlRpcValue param_array = XmlRpcValue::makeArray();

We created a array to pass to the server and opened a block try catch to capture a possible error.

param_array.arrayAppendItem(XmlRpcValue::makeInt(opp_1));
param_array.arrayAppendItem(XmlRpcValue::makeInt(opp_2));
param_array.arrayAppendItem(XmlRpcValue::makeDouble(opp_3));

We added to the array, the 3 values passed for parameters

string SERVER_URL = url.c_str();

Save in a variable the url the file config

XmlRpcClient server (SERVER_URL);

Initialize connect with the server.

XmlRpcValue result = server.call("sample.sumAndDifferen", param_array);

With server.call we called the function that is in the server and the pass the array with the data and in the variable result saved the result of the call.

XmlRpcValue::int32 sum = result.structGetValue("sum").getInt();
XmlRpcValue::int32 difference = result.structGetValue("difference").getInt();
double doble = result.structGetValue("doble").getDouble();

In this code we saved the data that the server returns us in variables

Accessing to the date with the object result and the funcion strucGetValue

 XmlRpcClient::Terminate();

With this we closed the client of RPC

cout << "Sum " << sum << " difference " << difference << " doble " << doble << endl;  

Print the result the server returned us

} catch (XmlRpcFault& fault) {
	cerr << ": XML-RPC fault #" << fault.getFaultCode() << ": " << fault.getFaultString() << endl;
    XmlRpcClient::Terminate();
    return 0;
}

Function to capture a possible error.

void msj(string sms){

This function is the same logic that sumAndDifferen, what change is we passed 1 string instead of integers

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

	int option = atof(argv[1]);
    int opp_1 = atoi(argv[2]);
    int opp_2 = atoi(argv[3]);
    double opp_3 = atof(argv[4]);

In this code we saved the arguments passed by the user

string sms = "LearnBiometric";

switch (option) {

	case 1:
		sumAndDifferen(opp_1, opp_2, opp_3);
	break;

	case 2:
		msj(sms);
	break;

	default:
	  cout<<"Error, bad input, quitting\n";
	break;

}

In this code we declared a struct control to to analyze the options passed by the user.

• If the user passed 1, we will execute the function sumAndDifferen

• If the user passed 2, we will execute the function msj

• If not is 1 or 2 print a error. This option not exist.

And we have already created our client

Now copile the client

Created a file compilar.sh with the instruction to compile that are the nexts:

#!/bin/sh

CC=gcc
CXX=g++
SRCS=client.cpp
CLIENT_CFLAGS=`xmlrpc-c-config c++ libwww-client --cflags`
CLIENT_LIBS=`xmlrpc-c-config c++ libwww-client --libs`
OBJS=client.o

g++ $CLIENT_CFLAGS -o $OBJS $SRCS $CLIENT_LIBS

And now execute

$ sh compilar.sh

3. Create the server

3.1 Create a directory to work:

$ mkdir server && cd server

3.2 Create a Header file the name server.h

This file contains all libraries of C++ that we need to work

With the following content:

#ifndef _Server_H_
#define _Server_H_

#include <xmlrpc.h>
#include <xmlrpc_cgi.h>
#include <XmlRpcCpp.h>
#include <stdio.h>
#include <string.h>
#include <cstdlib>
#include <iostream>

#define NAME       "XML-RPC Guide C++ Client"
#define VERSION    "0.1"

#endif

2.3 Create the logic of the server

Create a file server.cpp with the following content:

#include "server.h"

using namespace std;

xmlrpc_value *

sumAndDifference (xmlrpc_env *env, xmlrpc_value *param_array, void *user_data)
{
    if(user_data != NULL)
        user_data = NULL;
    
    xmlrpc_value * value;
    xmlrpc_int32 x, y; 
    xmlrpc_double doble;
    
    xmlrpc_array_read_item(env, param_array, 0, &value);
    xmlrpc_read_int(env, value, &x);
    xmlrpc_DECREF(value);
    
    xmlrpc_array_read_item(env, param_array, 1, &value);
    xmlrpc_read_int(env, value, &y);
    xmlrpc_DECREF(value);
    
    xmlrpc_array_read_item(env, param_array, 2, &value);
    xmlrpc_read_double(env, value, &doble);
    xmlrpc_DECREF(value);

    if(y != 0)
    {
        doble = ((double)x)/((double)y);
    }

    // Return our result.
    return xmlrpc_build_value(env, "{s:i,s:i,s:d}",
	                      "sum", x + y,
	                      "difference", x - y,
                          "doble", doble);
}

xmlrpc_value *

msj (xmlrpc_env *env, xmlrpc_value *param_array, void *user_data)
{
    if(user_data != NULL)
        user_data = NULL;

    xmlrpc_value * value;    
    const char * cadena;
    
    xmlrpc_array_read_item(env, param_array, 0, &value);
	xmlrpc_read_string(env, value, &cadena);
	xmlrpc_DECREF(value);
   
    // Return our result.
    return xmlrpc_build_value(env, "{s:s}",
	                      "message", cadena);
}

/**
 * @brief Main
 * @return Devuelve el estado del Main
 */

int main()
{
	/* Establece las bibliotecas CGI. */
	xmlrpc_cgi_init(XMLRPC_CGI_NO_FLAGS);

	/* Establece el tamaño límite del XMLRPC */
	xmlrpc_limit_set(XMLRPC_XML_SIZE_LIMIT_ID, 102400000);//5e6);

	xmlrpc_cgi_add_method_w_doc("sample.sumAndDifferen",
		                &sumAndDifference, NULL,
		                "S:ii", "Add and subtract two integers.");

	xmlrpc_cgi_add_method_w_doc("sample.msj",
		                &msj, NULL,
		                "S:ii", "Mensajito");

	/* Llama al método apropiado. */
	xmlrpc_cgi_process_call();

	/* Limpia nuestra biblioteca CGI. */
	xmlrpc_cgi_cleanup();

}

Now I will explain step by step the copied code

sumAndDifference (xmlrpc_env *env, xmlrpc_value *param_array, void *user_data){

This function calculates a sum, a subtraction and a division And @return The Struct result.

Recieve 3 parameters:

• @param env Variable XMLRPC de ambiente
• @param param_array Array que viene del cliente
• @param user_data Variables que vengan del usuario

xmlrpc_value * value;
xmlrpc_int32 x, y;
xmlrpc_double doble;

We declare the variables that we will use to the save the data And then use them in operations

xmlrpc_array_read_item(env, param_array, 0, &value);

this function read the item of array passed by the user in the position 0

xmlrpc_read_int(env, value, &x);

We assign the value to the variable x

xmlrpc_DECREF(value);

We release the memory

This repeat in the following lines

return xmlrpc_build_value(env, "{s:i,s:i,s:d}",
	                      "sum", x + y,
	                      "difference", x - y,
                          "doble", doble);                 

With this function return the information to client need

with xmlrpc_build_value we build a file struct (table hash)

and return the data to client in "{s:i,s:i,s:d}" this is the struc the message check that key sum is string and x + y is integer the same for the following lines.

msj (xmlrpc_env *env, xmlrpc_value *param_array, void *user_data)

This function is the same that sumAndDifference the only thing that changes is that it returns a string

• check:

return xmlrpc_build_value(env, "{s:s}",
	                      "message", cadena);

xmlrpc_cgi_init(XMLRPC_CGI_NO_FLAGS);

This function Sets the libraries CGI.

xmlrpc_limit_set(XMLRPC_XML_SIZE_LIMIT_ID, 102400000);

This function sets the size limit of the XMLRPC

xmlrpc_cgi_add_method_w_doc("sample.sumAndDifferen",
		                &sumAndDifference, NULL,
		                "S:ii", "Add and subtract two integers.");

This function allow to add a function at server and after the client can consult

Receives 5 parameters:

• sample.

• &

• NULL: Extra parameters.

• S:ii = Struc that return.

• A description the function.

xmlrpc_cgi_process_call();

This function call the method appropriate

xmlrpc_cgi_cleanup();

This function clean the libraries of CGI.

And we have already created our server

Now copile the server

Created a file compilar.sh with the instruction to compile that are the nexts:

#!/bin/sh

CLIENT_CFLAGS=`xmlrpc-c-config c++ libwww-client --cflags`
CLIENT_LIBS=`xmlrpc-c-config c++ libwww-client --libs`
CGI_CFLAGS=`xmlrpc-c-config cgi-server --cflags`
CGI_LIBS=`xmlrpc-c-config cgi-server --libs`

g++ $CGI_CFLAGS $CLIENT_CFLAGS \
  server.cpp -o \
  server.cgi \
  $CGI_LIBS $CLIENT_LIBS

mkdir -p /usr/lib/cgi-bin/server_pruebas/
cp server.cgi /usr/lib/cgi-bin/server_pruebas/

chmod 740 /usr/lib/cgi-bin/ -R
chown www-data:www-data /usr/lib/cgi-bin/ -R

Before compiling the code we need the binary of server.cgi

And now execute

$ sudo sh compilar.sh

To check the server run ok. In your browser check the url of the server:

http://localhost/cgi-bin/server_pruebas/server.cgi

And you should get this message:

405 Method Not Allowed An error occurred processing your request. XML-RPC Fault #-500: Expected HTTP method POST

Ok ok, Time to test the application

Go to directory client and execute the file client.o

Execute:

$ ./client.o 1 1 1 1

And you should get this message:

Archivo leído

url http://localhost/cgi-bin/server_pruebas/server.cgi
Sum 2 difference 0 doble 1

Now execute again but with the first parameter = 2

$ ./client.o 2 1 1 1

And you should get this message:

Archivo leído

url http://localhost/cgi-bin/server_pruebas/server.cgi
message LearnBiometric

Now play with that.