Thread: Hello, new here and need some help please

Hi guys, am new here so nice to meet u all
i have a problem with a certain client/server program.
the client sends a request to the server and asks it to add 100 to 1557. the server receives the request, does the computation and sends back the results as a string message. can any one help me do this please
Client code

Code:

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>    	/* defines structure in_addr */
#include <netdb.h>	   	/* defines structure hostent */
#include <stdio.h>
#include <string.h>
void main( int argc, char **argv)
{

  #define MAXCHAR 80

  int size_message, server_len, s; char client_message[MAXCHAR];

  struct sockaddr_in   client_addr, server_addr;

  struct hostent *server_ptr;

	/* create a connectionless socket with internet domain */
  s = socket(PF_INET,SOCK_DGRAM,0);

  	/* fill in data structure of client address */
  client_addr.sin_family = PF_INET;

  	/* accept connection on any internet interface */
  client_addr.sin_addr.s_addr = htonl (INADDR_ANY);

  	/* assign arbitrary port number */
  client_addr.sin_port= htons(0);

  	/* bind local address to the socket */
  bind(s,(struct sockaddr *)&client_addr,sizeof(client_addr)); 



/* get address of server and fill in its data structure */
  server_ptr = gethostbyname(argv[1]);
  server_addr.sin_family = PF_INET;
  server_addr.sin_addr= *(struct in_addr *)(server_ptr->h_addr); 
  server_addr.sin_port= htons(7785);
  	/* send server a message */
  strcpy (client_message,"ADD 100 to my Id 1557");
  size_message = strlen(client_message);
  printf("The message sent is &#37;s\n", client_message); 
  printf("The server internet address is %s\n",
				inet_ntoa(*server_ptr->h_addr_list)); 
  sendto(s,client_message,size_message,0,
              (struct sockaddr *)&server_addr,sizeof(server_addr));
}

Server code

Code:

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>    	/* defines structure in_addr */
#include <netdb.h>	  	/* defines structure hostent */
#include <stdio.h>
#include <string.h>
main()
{
  #define MAXCHAR 80
  int s;
  struct sockaddr_in    client_addr, server_addr;
  char server_message[MAXCHAR];
  int size_message, client_len;
  	/* create a connectionless socket with internet domain */
  s = socket(PF_INET,SOCK_DGRAM,0);
  	/* fill in data structure of server address */
  server_addr.sin_family = PF_INET;
  server_addr.sin_addr.s_addr = htonl (INADDR_ANY);
  server_addr.sin_port= htons(7785);
  	/* bind local address to the socket */
  bind(s,(struct sockaddr *) &server_addr, sizeof(server_addr)); 
	while(1) {

/* receive message from client */
  	/* recvfrom blocks until a message arrives */
  	/* it permits to retrieve the source address of message */
  client_len = sizeof (client_addr);
  recvfrom(s,server_message,MAXCHAR,0,
                  (struct sockaddr *)&client_addr,&client_len);
  printf("client address: %s\n", inet_ntoa(client_addr.sin_addr));
  printf("message received from client: %s\n",server_message);

	}
}

so pleeeeease can any one help me?? i'll be very grateful

thanks

So is this a
- communication problem (the message doesn't arrive)
- parsing problem (you don't know how to get "100" and "1557" out of the string)
- a math problem (how to do the addition)

Or something else?

Like for example
- does it compile?
- using ethereal / wireshark, can you see the message in transit at all?

Perhaps sscanf ?

Code:

#include <stdio.h>
int main(void)
{
	int a,b;
	char buf[] = "ADD 100 to my Id 1557";
	sscanf(buf,"ADD &#37;d to my Id %d", &a,&b);
	return 0;
}

Personally, I think you're missing a hell of a lot of basic information on C programming, and you've just launched yourself into the deep end with some network programming.

Unless you get this in place, then every small step towards whatever you want to do will be a struggle.

Perhaps you should ask your friend to join the forum and ask the questions directly.

You might also consider that if you're doing your friends' homework what exactly you're both getting out of this, because learning by doing is far more effective than just reading about it.

If you are trying to become a Formula One mechanic, you probably need to learn how to change the wheels on a regular car first. If you don't understand how to use sscanf() and the code-snippet posted, you probably should be studying the basics first. Network programming is not trivial.

--
Mats