NS_Provider_IPL4: map the IPL4 port to the system port before using it

Change-Id: Ia588ff82764e531c14665454eed035cd17b047ad
diff --git a/library/NS_Provider_IPL4.ttcn b/library/NS_Provider_IPL4.ttcn
index 5540d83..8ab8caa 100644
--- a/library/NS_Provider_IPL4.ttcn
+++ b/library/NS_Provider_IPL4.ttcn
@@ -26,6 +26,7 @@
 function main(NSConfiguration config) runs on NS_Provider_IPL4_CT {
 
 	/* connect socket */
+	map(self:IPL4, system:IPL4);
 	var Result res := f_IPL4_connect(IPL4, config.remote_ip, config.remote_udp_port, config.local_ip,
 					 config.local_udp_port, 0, { udp := {}});
 	if (not ispresent(res.connId)) {