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     Also  how to give ip-address in sin addr field

User · Answer

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

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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

User · Answer

In fact  AF  and PF  are the same thing  There are some words on Wikipedia will clear your confusion     The original design concept of the socket interface distinguished between protocol types  families  and the specific address types that each may use  It was envisioned that a protocol family may have several address types  Address types were defined by additional symbolic constants  using the prefix AF  instead of PF   The AF -identifiers are intended for all data structures that specifically deal with the address type and not the protocol family  However  this concept of separation of protocol and address type has not found implementation support and the AF -constants were simply defined by the corresponding protocol identifier  rendering the distinction between AF  versus PF  constants a technical argument of no significant practical consequence  Indeed  much confusion exists in the proper usage of both forms

User · Answer

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    amp addr sin addr

User · Answer

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

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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

User · Answer

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

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

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