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Full Discussion: Can't I Cast sockaddr to sockaddr_in?!
Top Forums Programming Can't I Cast sockaddr to sockaddr_in?! Post 302253502 by f.ben.isaac on Friday 31st of October 2008 07:38:25 PM
Old 10-31-2008
Can't I Cast sockaddr to sockaddr_in?!
I'm trying to grab client's port number, by doing the following code:

Code:
//get client's port number - here we are not dealing with pointers
//because the returned value will be passed as a parameter to htons()
//htons() takes u_short, which is similar to short, parameter
short get_client_port(struct sockaddr clientInformation)
{
    //carries the port number that client connected from
    short portNumber;
    
    //check the family version of client IP address, so you
    //can know where to cast, either to sockaddr_in or sockaddr_in6
    //and then grab the port after casting
    if (clientInformation.sa_family == AF_INET) {
        struct sockaddr_in ipv4 = (struct sockaddr_in)clientInformation;
        portNumber = ipv4.sin_port;
        return portNumber;
    }else{
        struct sockaddr_in6 ipv6 = (struct sockaddr_in6)clientInformation;
        portNumber = ipv6.sin6_port;
        return portNumber;
       }
}

In some point i did this:

Code:
short portNum =  get_client_port(clientInfo);
short portHostByte = ntohs(portNum);
//put portHostByte in a printf()

Why do i get the following errors?

Code:
echo_server.cpp: In function ‘short int get_client_port(sockaddr)':
echo_server.cpp:53: error: no matching function for call to ‘sockaddr_in::sockaddr_in(sockaddr&)'
/usr/include/netinet/in.h:218: note: candidates are: sockaddr_in::sockaddr_in()
/usr/include/netinet/in.h:218: note:                 sockaddr_in::sockaddr_in(const sockaddr_in&)
echo_server.cpp:57: error: no matching function for call to ‘sockaddr_in6::sockaddr_in6(sockaddr&)'
/usr/include/netinet/in.h:232: note: candidates are: sockaddr_in6::sockaddr_in6()
/usr/include/netinet/in.h:232: note:                 sockaddr_in6::sockaddr_in6(const sockaddr_in6&)

Any idea?
 

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LEARN ABOUT BSD

in

in.h(3HEAD)                                                           Headers                                                          in.h(3HEAD)

NAME

       in.h, in - Internet Protocol family

SYNOPSIS

       #include <netinet/in.h>

DESCRIPTION

       The <netinet/in.h> header defines the following types through typedef:

       in_port_t       An unsigned integral type of exactly 16 bits.

       in_addr_t       An  unsigned  integral  type  of exactly 32 bits. The <netinet/in.h> header defines the in_addr structure that includes the
                       following member:

       The <netinet/in.h> header defines the in_addr structure that includes the following member:

       in_addr_t       s_addr

       The <netinet/in.h> header defines the type sa_family_t as described in socket.h(3HEAD).

       The <netinet/in.h> header defines the following macros for use as values of the level argument of getsockopt() and setsockopt():

       IPPROTO_IP              Dummy for  IP

       IPPROTO_ICMP            Control message protocol

       IPPROTO_TCP             TCP

       IPPROTO_UDP             User datagram protocol The <netinet/in.h> header defines the following macros for use as destination addresses  for
                               connect(), sendmsg(), and sendto():

       INADDR_ANY              Local host address

       INADDR_BROADCAST        Broadcast address

       The  <netinet/in.h>  header  defines the sockaddr_in structure that is used to store addresses for the Internet protocol family.  Values of
       this type must be cast to struct sockaddr for use with the socket interfaces.

   Default
       For applications that do not require standard-conforming behavior (those that use the socket interfaces described in section(3SOCKET)  of
       the reference manual; see Intro(3) and standards(5)), the <netinet/in.h> header defines the sockaddr_in structure that includes the follow-
       ing members:

       sa_family_t     sin_family
       in_port_t       sin_port
       struct in_addr  sin_addr
       char            sin_zero[8]

   Standard conforming
       For applications that require standard-conforming behavior (those that use the socket interfaces described in section(3XNET) of the refer-
       ence  manual;  see Intro(3) and standards(5)), the <netinet/in.h> header defines the sockaddr_in structure that includes the following mem-
       bers:

       sa_family_t     sin_family
       in_port_t       sin_port
       struct in_addr  sin_addr
       unsigned char   sin_zero[8]

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Interface Stability          |Standard                     |
       +-----------------------------+-----------------------------+

SEE ALSO

       Intro(3), connect(3SOCKET), connect(3XNET),  getsockopt(3SOCKET),  getsockopt(3XNET),  sendmsg(3SOCKET),  sendmsg(3XNET),  sendto(3SOCKET),
       sendto(3XNET), setsockopt(3SOCKET), setsockopt(3XNET), socket.h(3HEAD), attributes(5), standards(5)

SunOS 5.10                                                          30 Aug 2002                                                        in.h(3HEAD)
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