Understanding INADDR ANY for socket programming

Question

I am trying to program some sockets and so  on the server side  I use htonl INADDR ANY   To the extent I understood  it seems to me that this function generates a random IP  am I correct     In fact  I want to bind my socket with my localhost  But if I run this   printf   d  htonl INADDR ANY      I get 0 as a return value  Could someone bring some explanation

User · Answer

To bind socket with localhost  before you invoke the bind function  sin addr s addr field of the sockaddr in structure should be set properly  The proper value can be obtained either by   my sockaddress sin addr s addr   inet addr  127 0 0 1     or by   my sockaddress sin addr s addr htonl INADDR LOOPBACK

User · Answer

INADDR ANY is used when you don t need to bind a socket to a specific IP  When you use this value as the address when calling bind    the socket accepts connections to all the IPs of the machine

User · Answer

INADDR ANY is a constant  that contain 0 in value   this will used only when you want connect from all active ports you don t care about ip-add   so if you want connect any particular ip you should mention like as   my sockaddress sin addr s addr   inet addr  192 168 78 2

User · Answer

INADDR ANY instructs listening socket to bind to all available interfaces  It s the same as trying to bind to inet addr  0 0 0 0    For completeness I ll also mention that there is also IN6ADDR ANY INIT for IPv6 and it s the same as trying to bind to    address for IPv6 socket    include  lt netinet in h gt   struct in6 addr addr   IN6ADDR ANY INIT    Also  note that when you bind IPv6 socket to to IN6ADDR ANY INIT your socket will bind to all IPv6 interfaces  and should be able to accept connections from IPv4 clients as well  though IPv6-mapped addresses

User · Answer

bind   of INADDR ANY does NOT  generate a random IP   It binds the socket to all available interfaces   For a server  you typically want to bind to all interfaces - not just  localhost    If you wish to bind your socket to localhost only  the syntax would be my sockaddress sin addr s addr   inet addr  127 0 0 1     then call bind my socket   SOCKADDR     amp my sockaddr         As it happens  INADDR ANY is a constant that happens to equal  zero    http   www castaglia org proftpd doc devel-guide src include inet h html    define INADDR ANY   unsigned long int  0x00000000        define INADDR NONE    0xffffffff       define INPORT ANY 0      If you re not already familiar with it  I urge you to check out Beej s Guide to Sockets Programming   http   beej us guide bgnet    Since people are still reading this  an additional note      man  7  ip       When a process wants to receive new incoming packets or connections    it should bind a socket to a local interface address using bind 2        In this case  only one IP socket may be bound to any given local    address  port  pair   When INADDR ANY is specified in the bind call    the socket will be bound to all local interfaces         When listen 2  is called on an unbound socket  the socket is   automatically bound to a random free port with the local address set   to INADDR ANY         When connect 2  is called on an unbound socket  the socket is   automatically bound to a random free port or to a usable shared port   with the local address set to INADDR ANY         There are several special addresses  INADDR LOOPBACK  127 0 0 1    always refers to the local host via the loopback device  INADDR ANY    0 0 0 0  means any address for binding      Also      bind       Bind a name to a   socket       If the  sin addr s addr  field is set to the constant INADDR ANY  as   defined in netinet in h  the caller is requesting that the socket be   bound to all network interfaces on the host  Subsequently  UDP packets   and TCP connections from all interfaces  which match the bound name    are routed to the application  This becomes important when a server   offers a service to multiple networks  By leaving the address   unspecified  the server can accept all UDP packets and TCP connection   requests made for its port  regardless of the network interface on   which the requests arrived

[c] Understanding INADDR_ANY for socket programming

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