diff --git a/qse/lib/cmn/mux.c b/qse/lib/cmn/mux.c
index d4554e60..3e5c486b 100644
--- a/qse/lib/cmn/mux.c
+++ b/qse/lib/cmn/mux.c
@@ -99,7 +99,10 @@ struct qse_mux_t
 
 	int kq;
 
-	/* event list: TODO: find the optimal size or make it auto-scalable */
+	/* kevent() places the events into the event list up to the limit specified.
+	 * this implementation passes the 'evlist' array to kevent() upon polling.
+	 * what is the best array size?
+	 * TODO: find the optimal size or make it auto-scalable. */
 	struct kevent evlist[512]; 
 	int size;
 	struct
@@ -296,7 +299,7 @@ int qse_mux_init (
 	mux->kq = kqueue ();
 	#endif
 	if (mux->kq <= -1)
-	{	
+	{
 		mux->errnum = skerr_to_errnum (errno);
 		return -1;
 	}
@@ -708,7 +711,7 @@ int qse_mux_delete (qse_mux_t* mux, const qse_mux_evt_t* evt)
 	}
 
 	mevt = mux->me.ptr[evt->hnd];
-	if (mevt->hnd != evt->hnd) 
+	if (!mevt || mevt->hnd != evt->hnd) 
 	{
 		/* already deleted??? */
 		mux->errnum = QSE_MUX_EINVAL;
@@ -756,7 +759,7 @@ done:
 	}
 
 	mevt = mux->me.ptr[evt->hnd];
-	if (mevt->hnd != evt->hnd) 
+	if (!mevt || mevt->hnd != evt->hnd) 
 	{
 		/* already deleted??? */
 		mux->errnum = QSE_MUX_EINVAL;
@@ -814,7 +817,7 @@ done:
 	}
 
 	mevt = mux->me.ptr[evt->hnd];
-	if (mevt->hnd != evt->hnd) 
+	if (!mevt || mevt->hnd != evt->hnd) 
 	{
 		/* already deleted??? */
 		mux->errnum = QSE_MUX_EINVAL;
@@ -889,8 +892,7 @@ int qse_mux_poll (qse_mux_t* mux, const qse_ntime_t* tmout)
 	ts.tv_nsec = tmout->nsec;
 
 	/* wait for events */
-	nevs = kevent (mux->kq, QSE_NULL, 0, 
-		mux->evlist, QSE_COUNTOF(mux->evlist), &ts);
+	nevs = kevent (mux->kq, QSE_NULL, 0, mux->evlist, QSE_COUNTOF(mux->evlist), &ts);
 	if (nevs <= -1) 
 	{
 		mux->errnum = skerr_to_errnum(errno);
diff --git a/qse/lib/http/httpd-std-dns.h b/qse/lib/http/httpd-std-dns.h
index 7f15c867..eacd937b 100644
--- a/qse/lib/http/httpd-std-dns.h
+++ b/qse/lib/http/httpd-std-dns.h
@@ -366,19 +366,32 @@ static int dns_open (qse_httpd_t* httpd, qse_httpd_dns_t* dns)
 #endif
 	if (!qse_isvalidsckhnd(dns->handle[0]) && !qse_isvalidsckhnd(dns->handle[1]))
 	{
+		/* don't set the error number here.
+		 * open_udp_socket() should set it */
 		goto oops;
 	}
 
 	/* carry on regardless of success or failure */
 	dc->skadlen = qse_nwadtoskad (&nwad, &dc->skad);
 
-	/* determine which socket to use when sending a request to the server */
+	/* determine which socket to use when sending a request to the default server */
 	if (dc->skadlen >=  0)
 	{
-		if (nwad.type == QSE_NWAD_IN4)
-			dc->dns_socket = dns->handle[0];
-		else
-			dc->dns_socket = dns->handle[1];
+		switch (nwad.type)
+		{
+			case QSE_NWAD_IN4:
+				dc->dns_socket = dns->handle[0];
+				break;
+
+			case QSE_NWAD_IN6:
+				dc->dns_socket = dns->handle[1];
+				break;
+
+			default:
+				/* unsupported address type for the default server */
+				dc->dns_socket = QSE_INVALID_SCKHND;
+				break;
+		}
 	}
 	else
 	{
@@ -870,10 +883,18 @@ printf ("DNS REALLY SENING>>>>>>>>>>>>>>>>>>>>>>>\n");
 		req->dns_skadlen = qse_nwadtoskad (&dns_server->nwad, &req->dns_skad);
 		if (req->dns_skadlen <= -1) goto default_dns_server;
 
-		if (dns_server->nwad.type == QSE_NWAD_IN4)
-			req->dns_socket = dns->handle[0];
-		else 
-			req->dns_socket = dns->handle[1];
+		switch (dns_server->nwad.type)
+		{
+			case QSE_NWAD_IN4:
+				req->dns_socket = dns->handle[0];
+				break;
+			case QSE_NWAD_IN6:
+				req->dns_socket = dns->handle[1];
+				break;
+			default:
+				qse_httpd_seterrnum (httpd, QSE_HTTPD_EINVAL);
+				goto oops;
+		}
 
 		dns_flags = dns_server->flags;
 	}
diff --git a/qse/lib/http/httpd-std-urs.h b/qse/lib/http/httpd-std-urs.h
index c0b966d5..b9e712ad 100644
--- a/qse/lib/http/httpd-std-urs.h
+++ b/qse/lib/http/httpd-std-urs.h
@@ -151,15 +151,15 @@ static int urs_open (qse_httpd_t* httpd, qse_httpd_urs_t* urs)
 		QSE_MEMSET (&dc->unix_bind_addr, 0, QSE_SIZEOF(dc->unix_bind_addr));
 		dc->unix_bind_addr.sun_family = AF_UNIX;
 	/* TODO: safer way to bind. what if the file name collides? */
+
 		qse_mbsxfmt (
 			dc->unix_bind_addr.sun_path, 
 			QSE_COUNTOF(dc->unix_bind_addr.sun_path),
-			QSE_MT("/tmp/.urs-%d-%ld-%ld"), 
-			(int)QSE_GETPID(), (long int)now.sec, (long int)now.nsec 
-		);
+			QSE_MT("/tmp/.urs-%x-%zx"), (int)QSE_GETPID(), (qse_size_t)dc);
 		QSE_UNLINK (dc->unix_bind_addr.sun_path);
 		if (bind (urs->handle[2], (struct sockaddr*)&dc->unix_bind_addr, QSE_SIZEOF(dc->unix_bind_addr)) <= -1)
 		{
+			qse_httpd_seterrnum (httpd, SKERR_TO_ERRNUM());
 			qse_closesckhnd (urs->handle[2]);
 			urs->handle[2] = QSE_INVALID_SCKHND;
 		}
@@ -170,6 +170,8 @@ static int urs_open (qse_httpd_t* httpd, qse_httpd_urs_t* urs)
 	    !qse_isvalidsckhnd(urs->handle[1]) &&
 	    !qse_isvalidsckhnd(urs->handle[2]))
 	{
+		/* don't set the error number here.
+		 * open_udp_socket() or bind() above should set the error number */
 		goto oops;
 	}
 
@@ -191,6 +193,7 @@ static int urs_open (qse_httpd_t* httpd, qse_httpd_urs_t* urs)
 				dc->urs_socket = urs->handle[2];
 				break;
 			default:
+				/* unsupported address for the default server */
 				dc->urs_socket = QSE_INVALID_SCKHND;
 				break;
 		}