write and read socket

lrios · 04-30-2008, 10:34 AM

Hi all,
In some situations my program respond, but in other situations the program don't respond for long time period, because client received more data. I am using bzero() and fflush() too.

What's wrong with the code ??

server

Code:

#define MAXL_NICK 256
char buffer_s[MAXL_NICK];		
char *welcome1 = "Write your nickname";
char *welcome2 = "Doing procedures . . .";
char *welcome3 = "please wait 5 second . . . ";

if((newsocket = accept(listenfd, (struct sockaddr *) &struc_server, &t_server)) < 0) { 

	         printf("error en el accept()\n");
		exit(-1);
		}

		else {			
	fflush(stdout);
	write(newsocket, welcome1, strlen(welcome1));
	bzero(buffer_s, MAXL_NICK);
 	read(newsocket, users[n_user].username, sizeof(users[n_user].username));
	printf("intented connected %s\n", users[n_user].username);
 	write(newsocket, welcome2, strlen (welcome2));
	write(newsocket, welcome3, strlen (welcome3));
	printf("connected %s \n", users[n_user].username);
	fflush(stdout);
	close(newsocket);
}}

}

client

Code:

#define MAXL_NICK 256
char buffer_c[MAXL_NICK];
	fflush(stdout);

	bzero(buffer_c, MAXL_NICK);
	read(sockfd, buffer_c, MAXL_NICK-1);
	printf("%s\n", buffer_c);
	fgets(buffer_c, sizeof(buffer_c), stdin);
	size_nick = strlen (buffer_c); 
	write(sockfd, buffer_c, size_nick-1);
	printf("sending to server the nick . . . %s", buffer_c);
	bzero(buffer_c, MAXL_NICK);
	read(sockfd, buffer_c, MAXL_NICK-1);
	printf("%s\n", buffer_c);
	bzero(buffer_c, MAXL_NICK);
	read(sockfd, buffer_c, MAXL_NICK-1);
	printf("%s\n", buffer_c);
	fflush(stdout);	

	close(sockfd);
	exit (0);

}

Can someone tell me what's wrong with this code
Thanx

ta0kira · 05-01-2008, 01:19 PM

Your server reads data the size of its entire username buffer, but the client only writes the amount of data typed in. You should write the entire buffer; not just strlen. Same with the server writes: they both use strlen but the client reads ask for a greater amount of data.
ta0kira

PS setlinebuf(stdout); will save you all of those fflush(stdout);s.

PPS If you don't want to write the entire buffer size, you could use fcntl(sockfd, F_SETFL, fcntl(sockfd, F_GETFL) | O_NONBLOCK); to set non-blocking mode, then use select right before your reads. This will allow your reads to read only the amount of data that was written instead of blocking for the entire requested size.