$OpenBSD$
--- net/net-ipv6.cpp.orig	Thu Aug 18 09:55:38 2011
+++ net/net-ipv6.cpp	Thu Aug 18 09:58:00 2011
@@ -258,6 +258,7 @@ int IP6Network::command(int argc, const char*const* ar
 int IP6Network::open(const char * host, int port, int ttl)
 {
 	char *g_addr;
+	Tcl& tcl = Tcl::instance();
 	// Check for SSM src address: Src,Group
 	if ((g_addr=(char *)strchr(host,(int)','))!=NULL) {
 		char s_addr_ssm[MAXHOSTNAMELEN];
@@ -291,6 +292,17 @@ int IP6Network::open(const char * host, int port, int 
 	}
 	(IP6Address&)local_ = local.sin6_addr;
 
+	/*
+	 * Check whether a local port to be used was specified on the commandline
+	 * If so, make sure that when setting RTP port, it is even, and RTCP uneven
+	 */
+	if (tcl.attr("localport") != NULL) {
+		int localport = atoi(tcl.attr("localport"));
+		if (ntohs(port) % 2 == 0)
+			port = (localport % 2 == 0) ? htons(localport) : htons(localport-1);
+		else
+			port = (localport % 2 == 0) ? htons(localport+1) : htons(localport);
+	}
 	rsock_ = openrsock(g_addr_, s_addr_ssm_, port, local_);
 	if (rsock_ < 0) {
 		(void)::close(ssock_);