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Client/Server sockets and reading a file

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Join Date: Jan 2008

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number87

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Client/Server sockets and reading a file

Feb 15th, 2009

So, what Im trying to do here is a client server socket program. The client will ask a question to the server. For example, How are you?
Then the server opens a text file, compares the string from the client and outputs the answer to the client.

My text file is something like this.
How are you? I am fine.

so client asks How are you?
server outputs to client I am fine.

So far I have tried compiling my code and there seems to be a compilation error. If I do not include the file reading and string checking, the client/server socket code works fine. As in I can make the server repeat whatever the client inputs.

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#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <iostream>
#include <cstring>
#include <string>
#include <fstream>
#include <vector>
#include <cstdlib>
#include <iostream>
using namespace std;
 
enum { RECV_PORT = 5000, MSGSIZE = 1024 };
const char fileName[30] = "file.txt";
char* s;
char input[255];
char* result = NULL;
string qns, ans;
socklen_t addr_len = sizeof(sockaddr) ;
 
int server( int socket_fd )
{
    sockaddr_in my_addr ;
    std::memset( &my_addr, 0, sizeof(my_addr) ) ;
    my_addr.sin_family = AF_INET ;
    my_addr.sin_port = htons( RECV_PORT ) ;
    my_addr.sin_addr.s_addr = INADDR_ANY ;
 
    if ( bind( socket_fd, (sockaddr*)&my_addr, addr_len ) != 0 )
       return 2 ;
 
    fstream infile(fileName);
    while( true )
    {
	infile.open(fileName);
 
        char recv_data[MSGSIZE+1] ;
        sockaddr_in client_addr ;
 
        int bytes_recd = recvfrom( socket_fd, recv_data, MSGSIZE, 0,
                                (sockaddr*)&client_addr, &addr_len ) ;
        if( bytes_recd == -1 ) 
	break ;
 
	else
	recv_data[bytes_recd] = '\0' ;
 
	{	
		infile.getline(input,255, '\n');
 
		while(!infile.eof())
		{
 
			vector<string> parts;
			std::string tmpstr(input);
			s = input;	
 
			result = strtok(s, " ");
 
			while (result != NULL)  
			{
				if (result != "" && result != "?.!") 
				{
					parts.push_back(result);
				}
 
         			result = strtok(NULL, "?.!");
     		}
 
		qns = parts[0];
		ans = parts[1];
 
		if (recv_data.compare(qns)==0)
		std::cout << ans << std::endl;
		}
 
 
	}	
 
        std::cout << "from " << inet_ntoa(client_addr.sin_addr)
                  << ':' << ntohs(client_addr.sin_port) << " - "
                  << recv_data << std::endl ;
    }
    return 0 ;
}
 
int client( int socket_fd )
{
    std::cout << "Enter Address to connect: " ;
    std::string address ; std::cin >> address >> std::ws ;
 
    sockaddr_in peer_addr ;
    std::memset( &peer_addr, 0, sizeof(peer_addr) ) ;
    peer_addr.sin_family = AF_INET ;
    peer_addr.sin_port = htons( RECV_PORT ) ;
    peer_addr.sin_addr.s_addr =
             *(in_addr_t*)(gethostbyname( address.c_str() )->h_addr) ;
 
    std::string send_str ;
    while( std::getline( std::cin, send_str ) )
    {
      send_str.resize(MSGSIZE) ;
      sendto( socket_fd, send_str.c_str(), MSGSIZE, 0,
            (sockaddr*)&peer_addr, addr_len ) ;
    }
    return 0 ;
}
 
int main()
{
 
 
 
 
  int socket_fd = socket( AF_INET, SOCK_DGRAM, 0 ) ;
  if( socket_fd == -1 ) return 1 ;
  return fork() == 0 ? server( socket_fd ) : client( socket_fd ) ;
}
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <iostream>
#include <cstring>
#include <string>
#include <fstream>
#include <vector>
#include <cstdlib>
#include <iostream>
using namespace std;

enum { RECV_PORT = 5000, MSGSIZE = 1024 };
const char fileName[30] = "file.txt";
char* s;
char input[255];
char* result = NULL;
string qns, ans;
socklen_t addr_len = sizeof(sockaddr) ;

int server( int socket_fd )
{
    sockaddr_in my_addr ;
    std::memset( &my_addr, 0, sizeof(my_addr) ) ;
    my_addr.sin_family = AF_INET ;
    my_addr.sin_port = htons( RECV_PORT ) ;
    my_addr.sin_addr.s_addr = INADDR_ANY ;

    if ( bind( socket_fd, (sockaddr*)&my_addr, addr_len ) != 0 )
       return 2 ;
	
    fstream infile(fileName);
    while( true )
    {
	infile.open(fileName);
			
        char recv_data[MSGSIZE+1] ;
        sockaddr_in client_addr ;

        int bytes_recd = recvfrom( socket_fd, recv_data, MSGSIZE, 0,
                                (sockaddr*)&client_addr, &addr_len ) ;
        if( bytes_recd == -1 ) 
	break ;
	
	else
	recv_data[bytes_recd] = '\0' ;
	
	{	
		infile.getline(input,255, '\n');
		
		while(!infile.eof())
		{
		
			vector<string> parts;
			std::string tmpstr(input);
			s = input;	

			result = strtok(s, " ");

			while (result != NULL)  
			{
				if (result != "" && result != "?.!") 
				{
					parts.push_back(result);
				}

         			result = strtok(NULL, "?.!");
     		}
		
		qns = parts[0];
		ans = parts[1];
		
		if (recv_data.compare(qns)==0)
		std::cout << ans << std::endl;
		}
		
	
	}	
	
        std::cout << "from " << inet_ntoa(client_addr.sin_addr)
                  << ':' << ntohs(client_addr.sin_port) << " - "
                  << recv_data << std::endl ;
    }
    return 0 ;
}

int client( int socket_fd )
{
    std::cout << "Enter Address to connect: " ;
    std::string address ; std::cin >> address >> std::ws ;

    sockaddr_in peer_addr ;
    std::memset( &peer_addr, 0, sizeof(peer_addr) ) ;
    peer_addr.sin_family = AF_INET ;
    peer_addr.sin_port = htons( RECV_PORT ) ;
    peer_addr.sin_addr.s_addr =
             *(in_addr_t*)(gethostbyname( address.c_str() )->h_addr) ;

    std::string send_str ;
    while( std::getline( std::cin, send_str ) )
    {
      send_str.resize(MSGSIZE) ;
      sendto( socket_fd, send_str.c_str(), MSGSIZE, 0,
            (sockaddr*)&peer_addr, addr_len ) ;
    }
    return 0 ;
}

int main()
{
	



  int socket_fd = socket( AF_INET, SOCK_DGRAM, 0 ) ;
  if( socket_fd == -1 ) return 1 ;
  return fork() == 0 ? server( socket_fd ) : client( socket_fd ) ;
}

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Join Date: Dec 2004

Posts: 2,413

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Comatose

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Taboo Programmer

Re: Client/Server sockets and reading a file

Feb 15th, 2009

First... I wouldn't make the text file in that way. I'd use a delimiter. Such as:

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Hello, How are you?:I'm fine.

This saves you the hassle of having to guess where the client sentence ends and the server sentence should begin. You already know... it's because of the :. I suppose the same could be said about the ?, but what if it now becomes a statement? Using a standard delimiter makes life that much easier.
As far as the code goes... it looks to me like your second strtok might throw things off result = strtok(NULL, "?.!"); doesn't match up with your first strtok, which is splitting by " ", not ?.!. You said above that there seems to be a compilation error... if so, what is the error?

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Join Date: Jan 2008

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number87

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Junior Poster in Training

Re: Client/Server sockets and reading a file

Feb 15th, 2009

the error is the recv_data type is not the same as my vector strings (qns and ans). So I am unable to string compare. And this is kind of a problem for me

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Join Date: Dec 2004

Posts: 2,413

Reputation: Comatose is a jewel in the rough

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Comatose

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Taboo Programmer

Re: Client/Server sockets and reading a file

Feb 15th, 2009

ah, yes. You could take the char array, and convert it to string, and then compare. While a bit of a pain I suppose:

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std::string tmpvar(recv_data);
if (tmpvar.compare(qns) == 0)
std::string tmpvar(recv_data);
if (tmpvar.compare(qns) == 0)

I think you could just do a simple == at that point though. if (tmpvar == qns) {

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Join Date: Jan 2008

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number87

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Junior Poster in Training

Re: Client/Server sockets and reading a file

Feb 16th, 2009

ok so now my code compiles properly. However, it doesnt work. I am able to input a question like How are you?
but nothing else happens. It should be able to create a fork and the server side of my code should be comparing the input with the file and displaying the answer.
Is there anything wrong with my file reading loop?

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <iostream>
#include <cstring>
#include <string>
#include <fstream>
#include <vector>
#include <cstdlib>
#include <iostream>
using namespace std;
 
enum { RECV_PORT = 5000, MSGSIZE = 1024 };
const char fileName[30] = "file.txt";
char* s;
char input[255];
char* result = NULL;
string qns, ans;
socklen_t addr_len = sizeof(sockaddr) ;
 
int server( int socket_fd )
{
    sockaddr_in my_addr ;
    std::memset( &my_addr, 0, sizeof(my_addr) ) ;
    my_addr.sin_family = AF_INET ;
    my_addr.sin_port = htons( RECV_PORT ) ;
    my_addr.sin_addr.s_addr = INADDR_ANY ;
 
    if ( bind( socket_fd, (sockaddr*)&my_addr, addr_len ) != 0 )
       return 2 ;
 
    fstream infile(fileName);
    while( true )
    {
	infile.open(fileName);
 
        char recv_data[MSGSIZE+1] ;
        sockaddr_in client_addr ;
 
        int bytes_recd = recvfrom( socket_fd, recv_data, MSGSIZE, 0,
                                (sockaddr*)&client_addr, &addr_len ) ;
        if( bytes_recd == -1 ) 
	break ;
 
	else
	recv_data[bytes_recd] = '\0' ;
 
	{	
		infile.getline(input,255, '\n');
 
		while(!infile.eof())
		{
 
			vector<string> parts;
			std::string tmpstr(input);
			s = input;	
 
			result = strtok(s, ":");
 
			while (result != NULL)  
			{
				if (result != "" && result != ":") 
				{
					parts.push_back(result);
				}
 
         			result = strtok(NULL, ":");
     		}
 
		qns = parts[0];
		ans = parts[1];
 
		std::string tmpvar(recv_data);
 
		if (tmpvar == qns)
		std::cout << ans << std::endl;
		}
 
 
	}	
	/*=====echo recv_data=====
        std::cout << "from " << inet_ntoa(client_addr.sin_addr)
                  << ':' << ntohs(client_addr.sin_port) << " - "
                  << recv_data << std::endl ;*/
    }
    return 0 ;
}
 
int client( int socket_fd )
{
    std::cout << "Enter Address to connect: " ;
    std::string address ; std::cin >> address >> std::ws ;
 
    sockaddr_in peer_addr ;
    std::memset( &peer_addr, 0, sizeof(peer_addr) ) ;
    peer_addr.sin_family = AF_INET ;
    peer_addr.sin_port = htons( RECV_PORT ) ;
    peer_addr.sin_addr.s_addr =
             *(in_addr_t*)(gethostbyname( address.c_str() )->h_addr) ;
 
    std::string send_str ;
    while( std::getline( std::cin, send_str ) )
    {
      send_str.resize(MSGSIZE) ;
      sendto( socket_fd, send_str.c_str(), MSGSIZE, 0,
            (sockaddr*)&peer_addr, addr_len ) ;
    }
    return 0 ;
}
 
int main()
{
 
 
 
 
  int socket_fd = socket( AF_INET, SOCK_DGRAM, 0 ) ;
  if( socket_fd == -1 ) return 1 ;
  return fork() == 0 ? server( socket_fd ) : client( socket_fd ) ;
}
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <iostream>
#include <cstring>
#include <string>
#include <fstream>
#include <vector>
#include <cstdlib>
#include <iostream>
using namespace std;

enum { RECV_PORT = 5000, MSGSIZE = 1024 };
const char fileName[30] = "file.txt";
char* s;
char input[255];
char* result = NULL;
string qns, ans;
socklen_t addr_len = sizeof(sockaddr) ;

int server( int socket_fd )
{
    sockaddr_in my_addr ;
    std::memset( &my_addr, 0, sizeof(my_addr) ) ;
    my_addr.sin_family = AF_INET ;
    my_addr.sin_port = htons( RECV_PORT ) ;
    my_addr.sin_addr.s_addr = INADDR_ANY ;

    if ( bind( socket_fd, (sockaddr*)&my_addr, addr_len ) != 0 )
       return 2 ;
	
    fstream infile(fileName);
    while( true )
    {
	infile.open(fileName);
			
        char recv_data[MSGSIZE+1] ;
        sockaddr_in client_addr ;

        int bytes_recd = recvfrom( socket_fd, recv_data, MSGSIZE, 0,
                                (sockaddr*)&client_addr, &addr_len ) ;
        if( bytes_recd == -1 ) 
	break ;
	
	else
	recv_data[bytes_recd] = '\0' ;
	
	{	
		infile.getline(input,255, '\n');
		
		while(!infile.eof())
		{
		
			vector<string> parts;
			std::string tmpstr(input);
			s = input;	

			result = strtok(s, ":");

			while (result != NULL)  
			{
				if (result != "" && result != ":") 
				{
					parts.push_back(result);
				}

         			result = strtok(NULL, ":");
     		}
		
		qns = parts[0];
		ans = parts[1];

		std::string tmpvar(recv_data);

		if (tmpvar == qns)
		std::cout << ans << std::endl;
		}
		
	
	}	
	/*=====echo recv_data=====
        std::cout << "from " << inet_ntoa(client_addr.sin_addr)
                  << ':' << ntohs(client_addr.sin_port) << " - "
                  << recv_data << std::endl ;*/
    }
    return 0 ;
}

int client( int socket_fd )
{
    std::cout << "Enter Address to connect: " ;
    std::string address ; std::cin >> address >> std::ws ;

    sockaddr_in peer_addr ;
    std::memset( &peer_addr, 0, sizeof(peer_addr) ) ;
    peer_addr.sin_family = AF_INET ;
    peer_addr.sin_port = htons( RECV_PORT ) ;
    peer_addr.sin_addr.s_addr =
             *(in_addr_t*)(gethostbyname( address.c_str() )->h_addr) ;

    std::string send_str ;
    while( std::getline( std::cin, send_str ) )
    {
      send_str.resize(MSGSIZE) ;
      sendto( socket_fd, send_str.c_str(), MSGSIZE, 0,
            (sockaddr*)&peer_addr, addr_len ) ;
    }
    return 0 ;
}

int main()
{
	



  int socket_fd = socket( AF_INET, SOCK_DGRAM, 0 ) ;
  if( socket_fd == -1 ) return 1 ;
  return fork() == 0 ? server( socket_fd ) : client( socket_fd ) ;
}

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Join Date: Oct 2006

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niek_e

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Cenosillicaphobiac

Re: Client/Server sockets and reading a file

Feb 16th, 2009

Without looking through all your code, I see this thing:

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	else
	recv_data[bytes_recd] = '\0' ;
	
	{
                 infile.getline(input,255, '\n');
		
		while(!infile.eof())

What is that brace doing there? That code block will always be executed, because the {}-block isn't part of any if/else/while/for block.

Last edited by niek_e; Feb 16th, 2009 at 9:07 am.

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Join Date: Jan 2008

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number87

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Junior Poster in Training

Re: Client/Server sockets and reading a file

Feb 17th, 2009

hmm i removed those braces and got the same results as I posted before.

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niek_e

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Cenosillicaphobiac

Re: Client/Server sockets and reading a file

Feb 17th, 2009

What I meant was: the braces are in the wrong place. The open brace should be directly after 'else'. How much experience do you have with c/c++? Perhaps you might want to read up on a if/else tutorial

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Join Date: Jan 2008

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number87

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Junior Poster in Training

Re: Client/Server sockets and reading a file

Feb 17th, 2009

forgot to mention that in my above post, but i tried putting the braces as you advised too. Both removing and changing the position of the braces resulted in the program doing nothing. Im not new to if else....
I am new to this socket and not sure how to integrate a file read/manipulation with the server part. As I said the echoing of input is fine. I believe it's the file read which makes my program not work but I don't know which part of the logic is wrong.

Last edited by number87; Feb 17th, 2009 at 8:36 pm.