ntohl function
Applies to: desktop apps only
The ntohl function converts a u_long from TCP/IP network order to host byte order (which is little-endian on Intel processors).
Syntax
u_long WSAAPI ntohl( __in u_long netlong );
Parameters
- netlong [in]
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A 32-bit number in TCP/IP network byte order.
Return value
The ntohl function returns the value supplied in the netlong parameter with the byte order reversed. If netlong is already in host byte order, then this function will reverse it. It is up to the application to determine if the byte order must be reversed.
Remarks
The ntohl function takes a 32-bit number in TCP/IP network byte order (the AF_INET or AF_INET6 address family) and returns a 32-bit number in host byte order.
The ntohl function can be used to convert an IPv4 address in network byte order to the IPv4 address in host byte order. This function does not do any checking to determine if the netlong parameter is a valid IPv4 address.
The ntohl function does not require that the Winsock DLL has previously been loaded with a successful call to the WSAStartup function.
Requirements
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Minimum supported client | Windows 2000 Professional |
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Minimum supported server | Windows 2000 Server |
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Header |
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Library |
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See also
- Winsock Reference
- Winsock Functions
- htonl
- htons
- inet_addr
- inet_ntoa
- InetNtop
- ntohs
- WSAHtonl
- WSAHtons
- WSANtohl
- WSANtohs
Send comments about this topic to Microsoft
Build date: 4/24/2012
"It is up to the application to determine if the byte order must be reversed."
It is up to the operating system providing this routine to determine if it actually does anything or not - not the application to detect if it should be used. Network byte order is big endian - on those machines this routine does nothing. On little endian machines, this function swaps the byte order.
If you're sending an integer over a network, you should call
valuetosend = hton*( value )to encode it and
value = ntoh*( receivedvalue )to decode it. Even if you're sending between two same endian machines, this will ensure that your code remains portable.
