Setting IP address to connect to

tesla · 09-11-2009, 10:10 PM

Hey, I'm pretty new to this networking stuff in C, and i just got a question abt some example code that i found. This is only part of the Client.c file.

The question is: I want the client to connect to the IP Address which i have to
explicitly set as 'localhost'. But I don't know exactly how I set the IPAddress that the client is to connect to, could someone please tell me where I do that and how?

Also,

Code:

socketAddr.sin_addr.s_addr = ipAddress->s_addr;	/* Copies IP address */

The comment on this code says, "copies IP address" why do you have to do that?

Thanx heaps,

Code:

int fd;
	struct in_addr* ipAddress;
	struct hostent* hostp;
	struct sockaddr_in socketAddr;
	char buffer[1024];
	int numBytes;

	hostp = gethostbyname("localhost");
	ipAddress = (struct in_addr*)hostp->h_addr_list[0];

	/* Specify the address we're going to connect to */
	socketAddr.sin_family = AF_INET;	/* Internet socket */
	socketAddr.sin_port = htons(13827);	/* Port number */
	socketAddr.sin_addr.s_addr = ipAddress->s_addr;	/* Copies IP address */

	/* Create TCP socket */
	fd = socket(AF_INET, SOCK_STREAM, 0);

	/* Try to connect to our server address */
	/* Address cast to generic socket address type, but we need to specify
	 ** the size of the address as the third argument */
	connect(fd, (struct sockaddr*)&socketAddr, sizeof(socketAddr));

tabstop · 09-11-2009, 10:49 PM

Quote:

Originally Posted by tesla

Hey, I'm pretty new to this networking stuff in C, and i just got a question abt some example code that i found. This is only part of the Client.c file.

The question is: I want the client to connect to the IP Address which i have to
explicitly set as 'localhost'. But I don't know exactly how I set the IPAddress that the client is to connect to, could someone please tell me where I do that and how?

Also,

Code:

socketAddr.sin_addr.s_addr = ipAddress->s_addr;	/* Copies IP address */

The comment on this code says, "copies IP address" why do you have to do that?

Thanx heaps,

Code:

int fd;
	struct in_addr* ipAddress;
	struct hostent* hostp;
	struct sockaddr_in socketAddr;
	char buffer[1024];
	int numBytes;

	hostp = gethostbyname("localhost");
	ipAddress = (struct in_addr*)hostp->h_addr_list[0];

	/* Specify the address we're going to connect to */
	socketAddr.sin_family = AF_INET;	/* Internet socket */
	socketAddr.sin_port = htons(13827);	/* Port number */
	socketAddr.sin_addr.s_addr = ipAddress->s_addr;	/* Copies IP address */

	/* Create TCP socket */
	fd = socket(AF_INET, SOCK_STREAM, 0);

	/* Try to connect to our server address */
	/* Address cast to generic socket address type, but we need to specify
	 ** the size of the address as the third argument */
	connect(fd, (struct sockaddr*)&socketAddr, sizeof(socketAddr));

Your second question is the answer to the first, and vice versa. You want to connect to localhost, so you need the IP address, so you go and get it (that's what gethostbyname does, get the host address from its name). Then you have to put into your socket object thing that you want to connect with.

**Salem** · 09-11-2009, 10:56 PM

So replace localhost with the name of the site you do want to connect to.

09-11-2009, 10:56 PM	#3
Salem and the hat of vanishing Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,214	So replace localhost with the name of the site you do want to connect to. __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut. Up to 8Mb PlusNet broadband from only £5.99 a month!
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