c program client server

Hello,

I have written a client and server c program, which I have taken from some example code. However, the program run ok, but I can't get anything back from the server. The client should send a single character and the server should increment and then send it back again.

Have I done anything wrong.

Please feel free to point out any bad programming code.

Many thanks for any suggestions,

Steve

My client code below:

Code:

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>


int main(int argc, char *argv[])
{
   printf("This is the client program\n");

   int sockfd;
   int len;
   struct sockaddr_in address;
   int result;
   char ch = 'A';

   //Create socket for client.
   sockfd = socket(AF_INET, SOCK_STREAM, 0);

   //Name the socket as agreed with server.
   address.sin_family = AF_INET;
   address.sin_addr.s_addr = inet_addr("127.0.0.1");
   address.sin_port = htons(7734);
   len = sizeof(address);

   //
   result = connect(sockfd, (struct sockaddr *)&address, len);

   if(result == 1)
   {
      perror("Error has occurred");
      exit(0);
   }

   //Read and write via sockfd
   write(sockfd, &ch, 1);
   read(sockfd, &ch, 1);
   printf("Char from server = %c\n", ch);
   close(sockfd);

   exit(0);
}

Server code:

Code:

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>


int main(int argc, char *argv[])
{
   //Declaring process variables.
   int server_sockfd, client_sockfd;
   int server_len, client_len;
   struct sockaddr_in server_address;
   struct sockaddr_in client_address;

   //Remove any old socket and create an unnamed socket for the server.
   server_sockfd = socket(AF_INET, SOCK_STREAM, 0);
   server_address.sin_family = AF_INET;
   server_address.sin_addr.s_addr = htons(INADDR_ANY);
   server_len = sizeof(server_address);

   bind(server_sockfd, (struct sockaddr *) &server_address, server_len);

   //Create a connection queue and wait for clients
   listen(server_sockfd, 5);
   while(1)
   {
      char ch;
      printf("server waiting\n");

      //Accept a connection
      client_len = sizeof(client_address);
      client_sockfd = accept(server_sockfd, (struct sockaddr *) &client_address, &client_len);

      //Read write to client on client_sockfd

      read(client_sockfd, &ch, 1);
      ch++;
      write(client_sockfd, &ch, 1);
      close(client_sockfd);
   }

   return 0;
}

You should check the return value from socket().

You should check the return value from read and write to see that the read and write operations go through OK - they can fail under some circumstances.

Likewise for bind() and listen()

You probably don't want to close the socket inside the while(1) loop, as that will prevent a second request from getting through.

--
Mats

I've gotten these working with each other.

CLIENT

Code:

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>


///   CLIENT   


int main(int argc, char *argv[])
{
	printf("This is the client program\n");

	int sockfd;
	int len, rc ;
	struct sockaddr_in address;
	int result;
	char ch = 'A';

   //Create socket for client.
	sockfd = socket(PF_INET, SOCK_STREAM, 0);
	if (sockfd == -1) { 
		perror("Socket create failed.\n") ; 
		return -1 ; 
	} 
	
	//Name the socket as agreed with server.
	address.sin_family = AF_INET;
	address.sin_addr.s_addr = inet_addr("127.0.0.1");
	address.sin_port = htons(7734);
	len = sizeof(address);

	result = connect(sockfd, (struct sockaddr *)&address, len);
	if(result == -1)
	{
		perror("Error has occurred");
		exit(-1);
	}

	while ( ch < 'Y') {

		//Read and write via sockfd
		rc = write(sockfd, &ch, 1);
		printf("write rc = &#37;d\n", rc ) ; 
		if (rc == -1) break ; 
		
		read(sockfd, &ch, 1);
		printf("Char from server = %c\n", ch);
		//if (ch == 'A') sleep(5) ;  // pause 5 seconds 
	} 
	close(sockfd);

	exit(0);
}

SERVER

Code:

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>

///   SERVER   

int main(int argc, char *argv[])
{
	//Declaring process variables.
	int server_sockfd, client_sockfd;
	int server_len ; 
	int rc ; 
	unsigned client_len;
	struct sockaddr_in server_address;
	struct sockaddr_in client_address;

	//Remove any old socket and create an unnamed socket for the server.
	server_sockfd = socket(AF_INET, SOCK_STREAM, 0);
	server_address.sin_family = AF_INET;
	server_address.sin_addr.s_addr = htons(INADDR_ANY);
	server_address.sin_port = htons(7734) ; 
	server_len = sizeof(server_address);

	rc = bind(server_sockfd, (struct sockaddr *) &server_address, server_len);
	printf("RC from bind = %d\n", rc ) ; 
	
	//Create a connection queue and wait for clients
	rc = listen(server_sockfd, 5);
	printf("RC from listen = %d\n", rc ) ; 

	client_len = sizeof(client_address);
	client_sockfd = accept(server_sockfd, (struct sockaddr *) &client_address, &client_len);
	printf("after accept()... client_sockfd = %d\n", client_sockfd) ; 

	while(1)
	{
		char ch;
		printf("server waiting\n");

		//Accept a connection
		//client_len = sizeof(client_address);
		//client_sockfd = accept(server_sockfd, (struct sockaddr *) &client_address, &client_len);
		//printf("after accept()... client_sockfd = %d\n", client_sockfd) ; 
		//Read write to client on client_sockfd

		rc = read(client_sockfd, &ch, 1);
		printf("RC from read = %d\n", rc ) ; 		
		if (ch=='X') break ; 
		ch++;
		write(client_sockfd, &ch, 1);
	}

	printf("server exiting\n");

	//close(client_sockfd);
	close(client_sockfd);
	return 0;
}

Todd

Thanks for your help,

Problem solved.