How to use the C socket API in C++ on z/OS

I've had no trouble using the BSD sockets API in C++, in GNU/Linux. Here's the sample program I used:

#include <sys/socket.h>

int
main()
{
    return AF_INET;
}

So my take on this is that z/OS is probably the complicating factor here, however, because I've never used z/OS before, much less programmed in it, I can't say this definitively. :-P

See the Using z/OS UNIX System Services sockets section in the z/OS XL C/C++ Programming Guide. Make sure you're including the necessary header files and using the appropriate #defines.

The link to the doc has changed over the years, but you should be able to get to it easily enough by finding the current location of the Support & Downloads section on ibm.com and searching the documentation by title.

So try

#define _OE_SOCKETS

before you include sys/socket.h

The _OE_SOCKETS appears to be simply to enable/disable the definition of socket-related symbols. It is not uncommon in some libraries to have a bunch of macros to do that, to assure that you're not compiling/linking parts not needed. The macro is not standard in other sockets implementations, it appears to be something specific to z/OS.

Take a look at this page:
Compiling and Linking a z/VM C Sockets Program

@Jax: The extern "C" thing matters, very very much. If a header file doesn't have one, then (unless it's a C++-only header file), you would have to enclose your #include with it:

extern "C" {
#include <sys/socket.h>
// include other similarly non-compliant header files
}

Basically, anytime where a C++ program wants to link to C-based facilities, the extern "C" is vital. In practical terms, it means that the names used in external references will not be mangled, like normal C++ names would. Reference.

You may want to take a look to cpp-sockets, a C++ wrapper for the sockets system calls. It works with many operating systems (Win32, POSIX, Linux, *BSD). I don't think it will work with z/OS but you can take a look at the include files it uses and you'll have many examples of tested code that works well on other OSs.

DISCLAIMER: I am not a C++ programmer, however I know C really well. I adapated these calls from some C code I have.

Also markdown put these strange _ as my underscores.

You should just be able to write an abstraction class around the C sockets with something like this:

class my_sock {
    private int sock;
    private int socket_type;
    private socklen_t sock_len;
    private struct sockaddr_in server_addr;
    public char *server_ip;
    public unsigned short server_port;
};

Then have methods for opening, closing, and sending packets down the socket.

For example, the open call might look something like this:

int my_socket_connect()
{
    int return_code = 0;

    if ( this->socket_type != CLIENT_SOCK ) {
        cout << "This is a not a client socket!\n";
        return -1;
    }

    return_code = connect( this->local_sock, (struct sockaddr *) &this->server_addr, sizeof(this->server_addr));

    if( return_code < 0 ) {
        cout << "Connect() failure! %s\n", strerror(errno);
        return return_code;
    }

    return return_code;
}