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Principle of inet_addr and inet_ntoa


 
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Old 11-11-2009
Principle of inet_addr and inet_ntoa

hello,
i have just started Socket programming and i come across functions
inet_addr() which converts IP address to unsigned long
and inet_ntoa() which converts unsigned long to IP address

but dont understand on what formula/principle they do these conversions
say for a given ip address can i expect what unsigned long number its going to give and vice versa.

one more thing:
i am writting a program , just to know how the above functions work but the difficulty is
i need to declare various structure variable , but how to know the exact names of the structures
i mean whether the structure is given in_addr_t or in_addr or some other name

can i see the structures and and its contents i am so confused.

please help me.
this is bit urgent and i want to learn it quickly.

Last edited by juststarted; 11-11-2009 at 09:28 AM..
 

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inet_addr(3XNET)				   X/Open Networking Services Library Functions 				  inet_addr(3XNET)

NAME
inet_addr, inet_network, inet_makeaddr, inet_lnaof, inet_netof, inet_ntoa - Internet address manipulation SYNOPSIS
cc [ flag ... ] file ... -lxnet [ library ... ] #include <arpa/inet.h> in_addr_t inet_addr(const char *cp); in_addr_t inet_lnaof(struct in_addr in); struct in_addr inet_makeaddr(in_addr_t net, in_addr_t lna); in_addr_t inet_netof(struct in_addr in); in_addr_t inet_network(const char *cp); char *inet_ntoa(struct in_addr in); DESCRIPTION
The inet_addr() function converts the string pointed to by cp, in the Internet standard dot notation, to an integer value suitable for use as an Internet address. The inet_lnaof() function takes an Internet host address specified by in and extracts the local network address part, in host byte order. The inet_makeaddr() function takes the Internet network number specified by net and the local network address specified by lna, both in host byte order, and constructs an Internet address from them. The inet_netof() function takes an Internet host address specified by in and extracts the network number part, in host byte order. The inet_network() function converts the string pointed to by cp, in the Internet standard dot notation, to an integer value suitable for use as an Internet network number. The inet_ntoa() function converts the Internet host address specified by in to a string in the Internet standard dot notation. All Internet addresses are returned in network order (bytes ordered from left to right). Values specified using dot notation take one of the following forms: a.b.c.d When four parts are specified, each is interpreted as a byte of data and assigned, from left to right, to the four bytes of an Internet address. a.b.c When a three-part address is specified, the last part is interpreted as a 16-bit quantity and placed in the rightmost two bytes of the network address. This makes the three-part address format convenient for specifying Class B network addresses as 128.net.host. a.b When a two-part address is supplied, the last part is interpreted as a 24-bit quantity and placed in the rightmost three bytes of the network address. This makes the two-part address format convenient for specifying Class A network addresses as net.host. a When only one part is given, the value is stored directly in the network address without any byte rearrangement. All numbers supplied as parts in dot notation may be decimal, octal, or hexadecimal, that is, a leading 0x or 0X implies hexadecimal, as specified in the ISO C standard; otherwise, a leading 0 implies octal; otherwise, the number is interpreted as decimal. USAGE
The return value of inet_ntoa() may point to static data that may be overwritten by subsequent calls to inet_ntoa(). RETURN VALUES
Upon successful completion, inet_addr() returns the Internet address. Otherwise, it returns (in_addr_t)(-1). Upon successful completion, inet_network() returns the converted Internet network number. Otherwise, it returns (in_addr_t)(-1). The inet_makeaddr() function returns the constructed Internet address. The inet_lnaof() function returns the local network address part. The inet_netof() function returns the network number. The inet_ntoa() function returns a pointer to the network address in Internet-standard dot notation. ERRORS
No errors are defined. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
endhostent(3XNET), endnetent(3XNET), attributes(5), standards(5) SunOS 5.11 10 Jun 2002 inet_addr(3XNET)

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