The C Programming Language

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Difference between htons() and htonl()? (lemmy.ml)

submitted 1 week ago* (last edited 1 week ago) by [email protected] to c/[email protected]

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Inside <arpa/inet.h>, there are two functions to convert host byte order to network byte order. Why are there two options? I understand that htons() is used for port address related to IPv4 and IPv6, but what use does htonl() serve?

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[–] [email protected] 1 points 1 week ago (1 children)

If I understood correctly, the difference is that the returned value is either uint16_t or uint32_t. Otherwise they look the same based on the headers and documentation.

[–] [email protected] 1 points 1 week ago (1 children)

But why two different functions? If I recall correctly, port address can be between 0 to 65535, which will fit under uint16_t. What use would uint32_t have? Is there any other use for htonl()?

[–] [email protected] 2 points 1 week ago

I don't usually use networking in C or C++, so I can't say for sure. But I did I find this quote that might explain it:

The reasons for having both 16 and 32 bit functions is that IP and TCP headers use a mix of 16-bit fields like port numbers along with 32-bit IPv4 addresses.