Add POSIX UDP server example

meson.build

@@ -43,3 +43,7 @@ endif
 if thread_dep.found()
     subdir('pthread')
 endif
+
+if host_machine.system() != 'windows'
+    subdir('posix')
+endif

posix/meson.build

+executable('udp-server', 'udp-server.c')

posix/udp-server.c

+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#define PORT 46123
+#define BUF_LENGTH 1024
+
+int
+main (void)
+{
+    int sock = socket (AF_INET, SOCK_DGRAM, 0);
+    if (sock == -1)
+    {
+        perror ("socket");
+        exit (EXIT_FAILURE);
+    }
+
+    struct sockaddr_in addr;
+    memset (&addr, 0, sizeof (struct sockaddr_in));
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons (PORT);
+    addr.sin_addr.s_addr = htonl (INADDR_ANY);
+
+    if (bind (sock, (struct sockaddr *) &addr, sizeof (addr)) == -1)
+    {
+        perror ("bind");
+        close (sock);
+        exit (EXIT_FAILURE);
+    }
+
+    while (true)
+    {
+        char buf[BUF_LENGTH];
+        struct sockaddr_in src_addr;
+        socklen_t addrlen = sizeof (struct sockaddr_in);
+        char str[INET_ADDRSTRLEN];
+
+        ssize_t bytes = recvfrom (sock, buf, BUF_LENGTH, 0,
+                                  (struct sockaddr *) &src_addr, &addrlen);
+        if (inet_ntop (AF_INET, &src_addr.sin_addr, str, INET_ADDRSTRLEN) == NULL)
+        {
+            fprintf (stderr, "Could not convert address to string\n");
+            exit (EXIT_FAILURE);
+        }
+
+        printf ("Received %zd bytes from %s\n", bytes, str);
+    }
+}