diff --git a/trunk/conf/rtc.conf b/trunk/conf/rtc.conf
index 03b42c75d..300b81d6f 100644
--- a/trunk/conf/rtc.conf
+++ b/trunk/conf/rtc.conf
@@ -3,6 +3,7 @@ listen              1935;
 max_connections     1000;
 srs_log_tank        console;
 srs_log_file        ./objs/srs.log;
+daemon              off;
 
 http_server {
     enabled         on;
@@ -21,10 +22,13 @@ rtc {
     enabled         on;
     # Listen at udp://8000
     listen          8000;
+    #
+    # The $CANDIDATE means fetch from env, if not configed, use default * as bellow.
+    #
     # The * means using IP of network interface stats.network,
     # For example, if stats.network=0, then use IP of eth0 as candidate.
     # @see https://github.com/ossrs/srs/issues/307#issuecomment-599028124
-    candidate       *;
+    candidate       $CANDIDATE;
 }
 
 vhost __defaultVhost__ {
diff --git a/trunk/research/players/rtc.html b/trunk/research/players/rtc.html
index 80cd1a2c0..550467aa1 100644
--- a/trunk/research/players/rtc.html
+++ b/trunk/research/players/rtc.html
@@ -16,7 +16,7 @@ rtc_media_player: <br>
 var PeerConnection = window.RTCPeerConnection || window.mozRTCPeerConnection || window.webkitRTCPeerConnection;
 var SessionDescription = window.RTCSessionDescription || window.mozRTCSessionDescription || window.webkitRTCSessionDescription;
 
-var url = "http://localhost:1985/api/v1/sdp/";
+var url = document.location.protocol + "//" + document.location.hostname + ":1985/api/v1/sdp/";
 
 var method = "POST";
 var shouldBeAsync = true;
diff --git a/trunk/src/app/srs_app_config.cpp b/trunk/src/app/srs_app_config.cpp
index cb47e12e0..b79fdadd7 100644
--- a/trunk/src/app/srs_app_config.cpp
+++ b/trunk/src/app/srs_app_config.cpp
@@ -4323,6 +4323,11 @@ std::string SrsConfig::get_rtc_candidates()
     if (!eip.empty()) {
         return eip;
     }
+
+    // If configed as ENV, but no ENV set, use default value.
+    if (srs_string_starts_with(conf->arg0(), "$")) {
+        return DEFAULT;
+    }
     
     return (conf->arg0().c_str());
 }