assigning a string

This is a discussion on assigning a string within the C Programming forums, part of the General Programming Boards category; Hello, I am doing some socket programming and have created a library. Code: int CreateSocket(char* domain, char* type, int protocal, ...

  1. #1
    UK2
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    Sep 2003
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    assigning a string

    Hello,

    I am doing some socket programming and have created a library.

    Code:
    int CreateSocket(char* domain, char* type, int protocal, unsigned int portNumber, char* IPAddress)
    {
    	struct sockaddr_in serverAddress;
    	int sockfd = 0;
    	int connectionResult = 0;
    
    	char family[10];
    
    	strcpy(family, domain);
    	printf("family = %s", family);
    	printf("Char* domain = %s\n", domain);
    	printf("(int) domain = %d\n", (int) domain);
    	printf("(int) *domain = %d\n", (int) *domain);
    
    	serverAddress.sin_family = *domain; //PROBLEM HERE ASSIGNING THE FAMILY DOMAIN.
     	serverAddress.sin_port = htons(portNumber);
     	serverAddress.sin_addr.s_addr = inet_addr(IPAddress);
    
    	memset(serverAddress.sin_zero, '\0', sizeof(serverAddress.sin_zero));
    	
    	sockfd = socket(PF_INET, SOCK_STREAM, 0);
    	printf("socket(PF_INET, SOCK_STREAM) = %d", sockfd);
    
    	if(sockfd == -1)
    	{
    		WriteErrorLog(1);
    		return -1;
    	}
    	.
            .
            .

    I have above function that will pass the address family (AF_INET) with some other parameters. The parameter name is domain.

    I think the problem is that the AF_INET is a key word so cannot assign a string representative. As you can see from my print outs I have tried many things.

    I need this parameter passed in as the user will either enter the address family or protocol family that they want to use. This will also be the same for the SOCK_STREAM or SOCK_DGRAM.

    Many thanks for any advice,

    Steve

  2. #2
    Banned master5001's Avatar
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    I think you already have an understanding of why the problem exists. I guess I have to know why you need to use strings for this instead of just using a short value or an int?

  3. #3
    UK2
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    Hello,

    I have just discovered that this works below:

    serverAddress.sin_family = (int) *domain;

    This gives the value of 65 that is assigned to the sin_family.

    I guess the 65 is the value that is assigned to the AF_INET. Correct if I am wrong.

    Steve

  4. #4
    Banned master5001's Avatar
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    Chars can lead to overflow/underflow problems when not explicitly casted. Though to answer your question, AF_INET is a platform specific value. So I guess it depends on what you are running. Though with a value like 65, I can't imagine a problem such as under/overflow.

  5. #5
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by steve1_rm View Post
    Hello,

    I have just discovered that this works below:

    serverAddress.sin_family = (int) *domain;

    This gives the value of 65 that is assigned to the sin_family.

    I guess the 65 is the value that is assigned to the AF_INET. Correct if I am wrong.

    Steve
    Well: you're wrong. 65 is the ASCII code for the letter 'A' (the first letter in "AF_INET").

    I don't know enough about networking to know what sin_family is defined to be. If it's also a char *, then you need to use strcpy to copy it over. If you're supposed to be using the int that AF_INET is #defined to be, then you shouldn't have a string in the first place.

    If worst comes to worst, you may have to parse the string yourself to convert string -> constant.

  6. #6
    Banned master5001's Avatar
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    ^ Bingo (about the string thing--which I questioned earlier too). I am not even finding a system that defines it as 65.

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