Originální popis anglicky: 
htonl, htons, ntohl, ntohs - convert values between host and network byte order
Návod, kniha: POSIX Programmer's Manual
#include <arpa/inet.h>
 
 
uint32_t htonl(uint32_t 
 hostlong);
 
uint16_t htons(uint16_t 
 hostshort);
 
uint32_t ntohl(uint32_t 
 netlong);
 
uint16_t ntohs(uint16_t 
 netshort);
 
These functions shall convert 16-bit and 32-bit quantities between network byte
  order and host byte order.
On some implementations, these functions are defined as macros.
The 
uint32_t and 
uint16_t types are defined in
  
<inttypes.h>.
The 
htonl() and 
htons() functions shall return the argument value
  converted from host to network byte order.
The 
ntohl() and 
ntohs() functions shall return the argument value
  converted from network to host byte order.
No errors are defined.
The following sections are informative.
None.
These functions are most often used in conjunction with IPv4 addresses and ports
  as returned by 
gethostent() and 
getservent().
None.
None.
endhostent() , 
endservent() , the Base Definitions volume of
  IEEE Std 1003.1-2001, 
<inttypes.h>,
  
<arpa/inet.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
  Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
  Operating System Interface (POSIX), The Open Group Base Specifications Issue
  6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
  Engineers, Inc and The Open Group. In the event of any discrepancy between
  this version and the original IEEE and The Open Group Standard, the original
  IEEE and The Open Group Standard is the referee document. The original
  Standard can be obtained online at http://www.opengroup.org/unix/online.html
  .