Setting IP address to connect to

This is a discussion on Setting IP address to connect to within the Networking/Device Communication forums, part of the General Programming Boards category; Hey, I'm pretty new to this networking stuff in C, and i just got a question abt some example code ...

  1. #1
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    Setting IP address to connect to

    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));

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    Posts
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    Quote Originally Posted by tesla View Post
    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.

  3. #3
    and the hat of int overfl Salem's Avatar
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    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.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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