Thread: how do firewalls work ? c socket question

my whole motivation for c programming is because i want to be able to make handy things like netcat and nmap etc .. im really not trying to be a hacker or anything gay like that. I just find that stuff interesting.

but just doing the basic socket stuff im doing at the minute i was wondering how you would go about programming a firewall.

I mean the only way i could think would be .. well i dont even know, do you have to create a socket on every port and listen for traffic? that sounds stupid so i doubt its that.

i just dont understand how it can monitor every port at the same time and report on it

thanks for the info mk.

Hey my other thread the code is quite long, i have simplified it here wondering if you can have a look, its very basic. I cant work out what the problem is though

i have a function

i pass it two variables makeConnection("127.0.0.1", 3000)

get the error cannot preform socket action on non socket. its really frustrating me now.

Code:

int makeConnection(char *ip, int port){
	int s;
	struct sockaddr_in connectto;
	if(s = socket(AF_INET,SOCK_STREAM,0) == -1) 
			bail("Socket Error"); 

	memset(&connectto,0,sizeof(connectto));
	connectto.sin_family = AF_INET;
	connectto.sin_addr.s_addr = inet_addr(ip);
	connectto.sin_port = htons(port);
	
	if (connect(s,(struct sockaddr *)&connectto,sizeof(connectto)) < 0) 
		bail("Connection Error");

	//we have connected.
	printf("We have connected.\n\n");

}

im stupid... lol thanks again for your help i appreciate it.