What is the difference between AF_INET and PF_INET in socket programming?

Question

What is the difference between AF_INET and PF_INET in socket programming?

I\'m confused between using AF_INET and PF_INET in socket() and bind()

Answer 1

Beej's famous network programming guide gives a nice explanation:

In some documentation, you'll see mention of a mystical "PF_INET". This is a weird etherial beast that is rarely seen in nature, but I might as well clarify it a bit here. Once a long time ago, it was thought that maybe a address family (what the "AF" in "AF_INET" stands for) might support several protocols that were referenced by their protocol family (what the "PF" in "PF_INET" stands for).
That didn't happen. Oh well. So the correct thing to do is to use AF_INET in your struct sockaddr_in and PF_INET in your call to socket(). But practically speaking, you can use AF_INET everywhere. And, since that's what W. Richard Stevens does in his book, that's what I'll do here.

Answer 2

AF_INET = Address Format, Internet = IP Addresses

PF_INET = Packet Format, Internet = IP, TCP/IP or UDP/IP

AF_INET is the address family that is used for the socket you're creating (in this case an Internet Protocol address). The Linux kernel, for example, supports 29 other address families such as UNIX sockets and IPX, and also communications with IRDA and Bluetooth (AF_IRDA and AF_BLUETOOTH, but it is doubtful you'll use these at such a low level).

For the most part sticking with AF_INET for socket programming over a network is the safest option.

Meaning, AF_INET refers to addresses from the internet, IP addresses specifically.

PF_INET refers to anything in the protocol, usually sockets/ports.

Answer 3

• AF = Address Family
• PF = Protocol Family

Meaning, AF_INET refers to addresses from the internet, IP addresses specifically. PF_INET refers to anything in the protocol, usually sockets/ports.

Consider reading the man pages for socket(2) and bind(2). For the sin_addr field, just do something like the following to set it:

struct sockaddr_in addr;
inet_pton(AF_INET, "127.0.0.1", &addr.sin_addr); 

Answer 4

Checking the header file solve's the problem. One can check for there system compiler.

For my system , AF_INET == PF_INET

AF == Address Family And PF == Protocol Family

Protocol families, same as address families.

Answer 5

There are situations where it matters.

If you pass AF_INET to socket() in Cygwin, your socket may or may not be randomly reset. Passing PF_INET ensures that the connection works right.

Cygwin is self-admittedly a huge mess for socket programming, but it is a real world case where AF_INET and PF_INET are not identical.

Answer 6

I found in Linux kernel source code that PF_INET and AF_INET are the same. The following code is from file include/linux/socket.h, line 204 of Linux kernel 3.2.21 tree.

/* Protocol families, same as address families. */
...
#define PF_INET     AF_INET