Re: [Dev-C++] Socket Programming - Newbie - sockaddr 16 bytes?

[Obi <ob...@ch...>]

At 02:20 07/11/2004 +0900, Peter Dennis wrote:

>Hi,
>
>Can someone tell me why it is important to fill out a sockaddr structure 
>to 16 bytes.
>
>Reading a book it says that the structure is as follows:
>
>struct sockaddr {
>    unsigned short    sa_family;
>    char                     sa_data[14];
>}
>
>Why fill it out to 16 bytes?  Is this a magic number in computers?
>
>If the address family I choose is AF_INET then how do I know that this 
>takes only 2 bytes in the structure?  Is there a way to calculate this?
>How do I know that I need to set sa_data to 14 and not 15?
>
>Any information regarding this would be great.
>
>Many thanks,
>Peter.

socakaddr is a generic structure for all family types used to pass addresses
to functions that don't depend on the family type.

If you use AF_INET you should use the sockaddr_in definition to manipulate
the data.

Use a reinterpret_cast<> to swap between the two defs for the
same in-memory data.

e.g.

         m_listenSocket = socket( AF_INET, SOCK_STREAM, 0 );

         // Bind Socket
         sockaddr_in lsa;
         memset( &lsa, 0, sizeof(lsa) );
         lsa.sin_family          = AF_INET;
         lsa.sin_port            = htons( LISTEN_PORT );
         lsa.sin_addr.s_addr     = htonl( INADDR_ANY );

         SOCKET ls;
         bind( ls, reinterpret_cast<sockaddr*>( &lsa ), sizeof(lsa) );

         // Listen on socket
         listen( ls, QSIZE );


Hope this helps,
O