not receiving messages in server/client program

[ueg1990]

hello,

i am trying to implement a tcp client and tcp server. i am able to establish the connection but when i send a message from client, the server is not able to receive it. here is my code below, if you can plz let me know what i am doi ng wrong, i wud really appreciate it. i think there is a problem in my server implementation

Client:

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


#define PORT 3490


int main(int argc, char *argv[])
{
	struct sockaddr_in server_info;
	struct hostent *he;
	int socket_fd,num;
	char *buffer;
	
	if (argc != 2) {
		fprintf(stderr, "Usage: client hostname\n");
		exit(1);
	}
	
	if ((he = gethostbyname(argv[1]))==NULL) {
		fprintf(stderr, "Cannot get host name\n");
		exit(1);
	}
	
	if ((socket_fd = socket(AF_INET, SOCK_STREAM, 0))== -1) {
		fprintf(stderr, "Socket Failure!!\n");
		exit(1);
	}
	
	memset(&server_info, 0, sizeof(server_info));
	server_info.sin_family = AF_INET;
	server_info.sin_port = htons(PORT);
	server_info.sin_addr = *((struct in_addr *)he->h_addr);
	if (connect(socket_fd, (struct sockaddr *)&server_info, sizeof(struct sockaddr))<0) {
		//fprintf(stderr, "Connection Failure\n");
		perror("connect");
		exit(1);
	}
	
	buffer = "Hello World!! I am networking!!\n";
	if ((send(socket_fd,buffer, sizeof(buffer),0))== -1) {
		fprintf(stderr, "Failure Sending Message\n");
		exit(1);
	}
	else {
		printf("Message being sent: %s\n",buffer);
	}
	close(socket_fd);	
	
}

Server:

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


#define PORT 3490
#define BACKLOG 10


int main()
{
	struct sockaddr_in server;
	struct sockaddr_in dest;
	int status,socket_fd, client_fd,size,num;
	char *buffer;
	int yes =1;
	
	memset(&server, 0, sizeof(server));
	server.sin_family = AF_INET;
	server.sin_port = htons(PORT);
	server.sin_addr.s_addr = INADDR_ANY; 
	
	if ((socket_fd = socket(AF_INET, SOCK_STREAM, 0))== -1) {
		fprintf(stderr, "Socket failure!!\n");
		exit(1);
	}
	
	if (setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1) {
        perror("setsockopt");
        exit(1);
    }
	
	if ((status = bind(socket_fd, (struct sockaddr *)&server, sizeof(struct sockaddr )))== -1)	 { //sizeof(struct sockaddr) 
		fprintf(stderr, "Binding Failure\n");
		exit(1);
	}
	
	if ((listen(socket_fd, BACKLOG))== -1){
		fprintf(stderr, "Listening Failure\n");
		exit(1);
	}
	while(1) {
		
		size = sizeof(dest);
		if ((client_fd = accept(socket_fd, (struct sockaddr *)&dest, &size)==-1)) {
			fprintf(stderr,"Accept Failure\n");
		}
		printf("Server got connection from client %s\n", inet_ntoa(dest.sin_addr));
		buffer = "Hello World!! I am networking!!\n";
	
		if ((num = recv(client_fd, buffer, 1024,0))== -1) {
			fprintf(stderr,"Error in receiving message!!\n");
			exit(1);
		}	
		buffer[num] = '\0';
		printf("Message received: %s\n", buffer); 
		close(client_fd);	
		//close(socket_fd);	
	}	
	
}

i would really appreciate some help.

[christop]

I don't see anything especially wrong in the client, but in the server you're not allocating space for the buffer. As it is, you're pointing buffer to a const char array (a string literal).

Instead of this:

 char *buffer;

You could do this:

 char buffer[1024+1]; // +1 for nul terminator

And remove the string literal.

[ueg1990]

i did that but still no result.

the error i am getting is on server side:

recv: Socket operation on non-socket

any other suggestions?? i am only one step away from establishing my client-server communication!!

[ueg1990]

since i am running both client and server on same machine, i run my program as:

for server:
gcc -o server ue_server.c
./server

for client:

gcc -o client ue_client.c
./client 127.0.0.1

[christop]

It's a bug with your parentheses:

 if ((client_fd = accept(socket_fd, (struct sockaddr *)&dest, &size)==-1)) {

Should be:

 if ((client_fd = accept(socket_fd, (struct sockaddr *)&dest, &size))==-1) {

Notice the movement of a closing parenthesis. Your version always set client_fd to 0 (or to 1 if accept failed).

[ueg1990]

yes, that was the mistake!!! thnx alot!!
i am able to now send and receive messages but only one at a time!!
how can i maintain a continuous connection?? so that if i send anything via client the server will echo it and viceversa and then the client/server waits for the next message??? shud i have another infinite while loop??