When and how to use C++ htonl function

c++ htonl
json27 picture json27 · May 22, 2015 · Viewed 14.9k times · Source 
cout << "Hello World !" << endl;

For my very first post on stackoverflow: When are we supposed to use the htonl function? I have gone through the man page. However, I don't really understand when and how to use it.

Answer

user4581301 picture user4581301 · May 22, 2015

Host TO Network translation. It makes sure the endian of a 32 bit data value is correct (Big endian) for network transport. ntohl -- Network TO Host -- is used by the receiver to ensure that the endian is correct for the receiver's CPU. Keep an eye out for htons and ntohs for handling 16 bits, and out there somewhere are likely htonll and ntohll for 64 bits.

Using all of them is as simple as pass in the number you want converted and out comes the converted number. You may find that absolutely nothing has happened on some processors because their endian is already big.

uint32_t inval = 0xAABBCCDD;
uint32_t outval = htonl(inval);

Will, on most desktop hardware, result in outval being set to 0xDDCCBBAA

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