htonl - Man Page

convert values between host and network byte order


This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.


#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>.

Return Value

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.



Application Usage

These functions are most often used in conjunction with IPv4 addresses and ports as returned by gethostent() and getservent().



Future Directions


See Also

endhostent(), endservent()

The Base Definitions volume of POSIX.1-2017, <arpa_inet.h>, <inttypes.h>

Referenced By

arpa_inet.h(0p), endservent(3p), netinet_in.h(0p).

2017 IEEE/The Open Group POSIX Programmer's Manual