Socket Question

[DaveHope]

Hello all.

Firstly, I wasn't sure if this should go in the Networking forum or in the C++ forum, so I posted it here as I figured the C++ people are more likely to look here than the networking one. We'll seoon see

I've been toying with C for a while, just brought C++ for Dummies figuring I'd consider moving over. Anyway, looking at some socket stuff (not covered by the book, annoyingly) and have followed Beej's network tutorial. However, I'm wondering how I can recieve more that one line of input from a server. I'm assuming I need a while() look in here somewhere, chekcing for multiple lines. Not entirely sure where, and seeing as the tutorial didn't cover it I figured I'd ask

main.cpp

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

#include "Config.cpp"

using namespace std;

int main(int argc, char *argv[])
{
	/* Setup the configration options. */
	Configuration.Server = "irc.blitzed.org";
	Configuration.Channel = "#testing12345";
	Configuration.RealName = "Test, from DaveHope";
	Configuration.Port = 6667;
	Configuration.DataSize = 100;
	Configuration.Debug = 1;

	int sockfd, numbytes;  
	char buf[Configuration.DataSize];
	struct hostent *he;
	struct sockaddr_in their_addr; // connector's address information 

	if ((he=gethostbyname(Configuration.Server)) == NULL) {
		perror("gethostbyname");
		exit(1);
	}

	if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
		perror("socket");
		exit(1);
	}

	their_addr.sin_family = AF_INET;    // host byte order 
	their_addr.sin_port = htons(Configuration.Port);  // short, network byte order 
	their_addr.sin_addr = *((struct in_addr *)he->h_addr);
	memset(&(their_addr.sin_zero), '\0', 8);  // zero the rest of the struct 

	if (connect(sockfd, (struct sockaddr *)&their_addr, sizeof(struct sockaddr)) == -1) {
		perror("connect");
		exit(1);
	}

	if ((numbytes=recv(sockfd, buf, Configuration.DataSize-1, 0)) == -1) {
		perror("recv");
		exit(1);
	}

	buf[numbytes] = '\0';

	printf("%s\n",buf);

	/* Close the connection. */
	close(sockfd);

	/* Exit. */
	return 0;
}

Config.cpp

/*
 *  Configuration Array.
 *  The below struct will hold all configuration information.
 */

struct Configuration
{
	/* General Configuration. */
	int Port;
	char *Server;
	char *Channel;
	char *Nickname;
	char *RealName;
	int DataSize;
   
	/* Debug Mode ? */
	int Debug;
	
	/* Socket/Connection Configuration. */
	int state;	
};

struct Configuration Configuration;

As always, you guys are stars. Thanks for putting up with my so far!

[sean]

Networking would be the correct place. Moved.

[DaveHope]

Networking would be the correct place. Moved.

Typical. 50/50 chance and i guess the wrong one. Ahh well

[sean]

Anyway, to answer your question, you can call recv() multiple times - it works just like any other input function - so a loop testing for when input stops would work.

[DaveHope]

So, something like the following perhaps ?

int tmp;
while (true) {
tmp = recv(sockfd, buf, Configuration.DataSize-1, 0);
if (tmp == -1) {
		perror("recv");
		exit(1);
	}

	buf[numbytes] = '\0';

	printf("%s\n",buf);
}

[sean]

Looks decent - but it's been a really long time since I used sockets outside of C#, so I would wait until someone more experienced confirms that before using it.

[DaveHope]

Well, just tried it and it segfaults (compiles without any wanrnings though), so I'll sit and wait

[DaveHope]

Just had some help from a friend, I was indeed missing a loop - I just implimented it wrong in my attempt. In case anyone has a similar problem, here's the changed code.

	do {
		if ((numbytes=recv(sockfd, buf, Configuration.DataSize-1, 0)) == -1) {
			perror("recv");
			exit(1);
		}

		buf[numbytes] = '\0';

		printf("%s\n",buf);
	} while(numbytes);

[Hammer]

You could get multiple lines of text with only one call to recv().
http://faq.cprogramming.com/cgi-bin/...&id=1044780608

[DaveHope]

Alright, I'm now having problems sending data back. At current, I have the following in my do{} loop.

		if (!Configuration.State) {
			tmp = "USER: test localhost localhost :test\n\r";
			send(sockfd, tmp, strlen(tmp), 0);
			tmp = "NICK: test\n\r";
			send(sockfd, tmp, strlen(tmp), 0);
			Configuration.State = 1;
		}

For some reason, it never seems to send it (but doesn't give an error). Checked, and it does get inside the if statement, just doesn't send the data or error. Suggestions anyone ?

[DaveHope]

Sorted. Was a simple misreading of the RFC for that one. - the ':' arn't supposed to be there, that'll teach me not to clean the marks off my monitor.

[Hammer]

You'd also do well by checking the return code from the send() function to ensure it's worked as requested.

[DaveHope]

Yea, in the real code I am doing. It's now OO too. I just like to get things working in their absolute basics before taking that section of code further