OpenBSD Socket Programming

Question

There's a dynamic IP address (the public IP of my home) that I'd like to track (i.e., have it as a file on my OpenBSD server). I came up with this simple server:

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<unistd.h>

int
main(int argc, char *argv[])
{
    int             socket_desc,
                    new_socket,
                    c;
    struct sockaddr_in server,
                    client;
    char           *message;

    socket_desc = socket(AF_INET, SOCK_STREAM, 0);
    if (socket_desc == -1) {
        return 1;
    }

    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(1234);

    if (bind(socket_desc, (struct sockaddr *) &server, sizeof(server)) < 0) {
        return 2;
    }

    listen(socket_desc, 3);

    for (;;) {
        c = sizeof(struct sockaddr_in);
        new_socket =
            accept(socket_desc, (struct sockaddr *) &client,
                   (socklen_t *) & c);
        if (new_socket < 0) {
            return 3;
        }

        int             client_port = ntohs(client.sin_port);
        char           *client_ip = inet_ntoa(client.sin_addr);
        for (int i = 0; i < 100; ++i) {
            if (client_ip[i] == 0)
                break;
            printf("%c", client_ip[i]);
        }
        printf("\n");
        write(new_socket, client_ip, strlen(client_ip));
        write(new_socket, "\n", 1);
    }
    return 0;
}

I developed it on my Raspberry Pi (my main computer), running Raspberry Pi OS Buster (basically Debian GNU/Linux Buster). It compiles well with both gcc(1) and tcc(1). Same on my x86_64 Artix Linux laptop. However, when I tried it on OpenBSD with cc(1) (which is Clang), I receive:

iplog4.c:14:24: error: variable has incomplete type 'struct sockaddr_in'
    struct sockaddr_in server,
                       ^
iplog4.c:14:12: note: forward declaration of 'struct sockaddr_in'
    struct sockaddr_in server,
           ^
iplog4.c:15:21: error: variable has incomplete type 'struct sockaddr_in'
                    client;
                    ^
iplog4.c:14:12: note: forward declaration of 'struct sockaddr_in'
    struct sockaddr_in server,
           ^
iplog4.c:26:30: error: use of undeclared identifier 'INADDR_ANY'
    server.sin_addr.s_addr = INADDR_ANY;
                             ^
iplog4.c:39:13: error: invalid application of 'sizeof' to an incomplete type 'struct sockaddr_in'
        c = sizeof(struct sockaddr_in);
            ^     ~~~~~~~~~~~~~~~~~~~~
iplog4.c:14:12: note: forward declaration of 'struct sockaddr_in'
    struct sockaddr_in server,
           ^
4 errors generated.

Answer 1

You need the following include to make it compile:

#include <netinet/in.h>