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Full Discussion: get host name by IP address
Top Forums Programming get host name by IP address Post 302381145 by limmer on Thursday 17th of December 2009 09:12:39 AM
Old 12-17-2009
I finally got it working:

Code:
char *IPtoHOST(const char *IP) // returns host name from IP address. If failure, returns IP address.
{
	static char BUFFER[65] = "";

	struct sockaddr_in SIN; // create a struct of sockaddr_in type
	memset(&SIN, 0, sizeof(SIN)); // zero SIN struct before use
	SIN.sin_family		= AF_INET; // specify address family
	SIN.sin_addr.s_addr	= inet_addr(IP); // pass the IP
	SIN.sin_port		= 0; // specify port: 0 is chosen by the system. htons(port) is for manual specification (it seems to work specifying any port so I let system choose)

	getnameinfo( (struct sockaddr *)&SIN /* type cast sockaddr_in to sockaddr */, sizeof(SIN), BUFFER, 64, NULL, 0, 0); // If the last parameter (flags) is 0 and if getnameinfo fails, then the IP is written into BUFFER instead of the host name

	return BUFFER;
}


Last edited by limmer; 04-08-2010 at 04:38 PM..
 

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SIN(3)							     Linux Programmer's Manual							    SIN(3)

NAME
sin, sinf, sinl - sine function SYNOPSIS
#include <math.h> double sin(double x); float sinf(float x); long double sinl(long double x); Link with -lm. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): sinf(), sinl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99 DESCRIPTION
The sin() function returns the sine of x, where x is given in radians. RETURN VALUE
On success, these functions return the sine of x. If x is a NaN, a NaN is returned. If x is positive infinity or negative infinity, a domain error occurs, and a NaN is returned. ERRORS
See math_error(7) for information on how to determine whether an error has occurred when calling these functions. The following errors can occur: Domain error: x is an infinity An invalid floating-point exception (FE_INVALID) is raised. These functions do not set errno. CONFORMING TO
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89. SEE ALSO
acos(3), asin(3), atan(3), atan2(3), cos(3), csin(3), sincos(3), tan(3) COLOPHON
This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2009-02-04 SIN(3)
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