0

My distro is MX Linux (Debian) GCC was already installed with distro.

I am trying to compile some open source code from Nir Lictman. His Minimalist C web server code compiles in his YouTube video.

When I use gcc to compile, I get errors:

servera.c: In function ‘main’:
servera.c:21:13: warning: passing argument 2 of ‘bind’ from incompatible pointer type [-Wincompatible-pointer-types]
   21 |     bind(s, &addr, sizeof(addr));
      |             ^~~~~
      |             |
      |             struct sockaddr_in *
In file included from servera.c:1:
/usr/include/x86_64-linux-gnu/sys/socket.h:112:49: note: expected ‘const struct sockaddr *’ but argument is of type ‘struct sockaddr_in *’
  112 | extern int bind (int __fd, __CONST_SOCKADDR_ARG __addr, socklen_t __len)

When I try to see the man page for netinet i get error:

$ man netinet
No manual entry for netinet

I did find a netinet directory that contains in.h at /usr/include/netinet. And that in.h has a definition of sockaddr_in as follows:

/* Structure describing an Internet socket address.  */
struct sockaddr_in
  {
    __SOCKADDR_COMMON (sin_);
    in_port_t sin_port;         /* Port number.  */
    struct in_addr sin_addr;        /* Internet address.  */

    /* Pad to size of `struct sockaddr'.  */
    unsigned char sin_zero[sizeof (struct sockaddr)
               - __SOCKADDR_COMMON_SIZE
               - sizeof (in_port_t)
               - sizeof (struct in_addr)];
  };

However I wonder if the compiler is finding this definition.

Improve this question

1 Answer 1

Reset to default
2

See the example in man 2 bind: standard practice here is to cast the pointer to the expected type. In your example:

    bind(s, (const struct sockaddr *) &addr, sizeof(addr));
Improve this answer
4
  • Thank you Stephen. It compiles now ! Did I get the port code correct? I run the executable. I put simple index.htm in dir with this executable file. When I run the code and then browse with Firefox to either 127.0.0.1:8080/index.htm or 192.168.0.101:8080/index.htm I get Error, "Unable to Connect". Commented Dec 29, 2023 at 21:27
  • It works for me on 8080, as long as nothing else is already bound to that port; the program doesn’t handle errors, so if it fails to bind it will silently bind to a random port. Commented Dec 30, 2023 at 11:12
  • Thanks Stephen. Thanks for hanging in there with me. I added many error traps: socket, bind, listen, accept, recv. All browsers say"connection refused". However, WGET actually works and reports "no headers. HTTP 0.9 assumed". And it DOES INDEED download the file. So I guess I have to somehow dress up the the response with headers to get minimal functionality with a browser - which is useful for me. Thank you again, my friend :-) Commented Dec 31, 2023 at 15:20
  • Oh right, yes, it won’t work with a modern browser (but I’d expect “connection reset” rather than “refused”). Commented Dec 31, 2023 at 15:39

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.