add a simple example how to properly let the IP stack choose a free port number

git-svn-id: file:///home/lennart/svn/public/avahi/trunk@1438 941a03a8-eaeb-0310-b9a0-b1bbd8fe43fe

diff --git a/docs/socket-auto-port.c b/docs/socket-auto-port.c
new file mode 100644 (file)
index 0000000..850759a
--- /dev/null
+++ b/docs/socket-auto-port.c
@@ -0,0 +1,48 @@
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <arpa/inet.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <stdio.h>
+
+int main(int argc, char *argv[]) {
+    int s;
+    struct sockaddr_storage sa;
+    socklen_t salen;
+    uint16_t port;
+    
+    if ((s = socket(PF_INET6, SOCK_STREAM, 0)) < 0) {
+        if (errno == EAFNOSUPPORT)
+            s = socket(PF_INET, SOCK_STREAM, 0);
+    
+        if (s < 0) {
+            perror("socket()");
+            return 1;
+        }
+    }
+
+    if (listen(s, 2) < 0) {
+        perror("listen()");
+        return 2;
+    }
+
+    salen = sizeof(sa);
+    if (getsockname(s, (struct sockaddr*) &sa, &salen) < 0) {
+        perror("getsockname()");
+        return 3;
+    }
+
+    if (((struct sockaddr*) &sa)->sa_family == AF_INET)
+        port = ((struct sockaddr_in*) &sa)->sin_port;
+    else
+        port = ((struct sockaddr_in6*) &sa)->sin6_port;
+
+    printf("Selected port number %u\n", ntohs(port));
+
+    /* ... hic sunt leones ... */
+
+    sleep(60);
+    
+    return 0;
+}