diff --git a/trunk/conf/full.conf b/trunk/conf/full.conf
index 8bf44582b..c630002fd 100644
--- a/trunk/conf/full.conf
+++ b/trunk/conf/full.conf
@@ -396,6 +396,11 @@ rtc_server {
     # @see https://github.com/ossrs/srs/wiki/v4_CN_WebRTC#config-candidate
     # default: *
     candidate *;
+    # If api_as_candidates is on, SRS would try to use the IP of api server, specified by srs.sdk.js request:
+    #       api:string "http://r.ossrs.net:1985/rtc/v1/play/"
+    # in this case, the r.ossrs.net and 39.107.238.185 will be added as candidates.
+    # Default: on
+    api_as_candidates on;
     # The IP family filter for auto discover candidate, it can be:
     #       ipv4        Filter IP v4 candidates.
     #       ipv6        Filter IP v6 candidates.
diff --git a/trunk/doc/CHANGELOG.md b/trunk/doc/CHANGELOG.md
index 273f059fc..f7f97ffe1 100644
--- a/trunk/doc/CHANGELOG.md
+++ b/trunk/doc/CHANGELOG.md
@@ -8,6 +8,7 @@ The changelog for SRS.
 
 ## SRS 4.0 Changelog
 
+* v4.0, 2021-01-04, Discover api server and ip as candidates. v4.0.218
 * v4.0, 2021-01-04, Install test-on self-sign certificate. v4.0.217
 * v4.0, 2021-01-03, For [#2824](https://github.com/ossrs/srs/issues/2824): Support config in_docker to fix the detect fail. (#2824). v4.0.216
 * v4.0, 2021-12-31, For [#2728](https://github.com/ossrs/srs/issues/2728): Refine error log for rtmp2rtc. (#2728). v4.0.215
diff --git a/trunk/src/app/srs_app_config.cpp b/trunk/src/app/srs_app_config.cpp
index d6ea94634..a984b4cd8 100644
--- a/trunk/src/app/srs_app_config.cpp
+++ b/trunk/src/app/srs_app_config.cpp
@@ -2542,7 +2542,7 @@ srs_error_t SrsConfig::check_normal_config()
             string n = conf->at(i)->name;
             if (n != "enabled" && n != "listen" && n != "dir" && n != "candidate" && n != "ecdsa"
                 && n != "encrypt" && n != "reuseport" && n != "merge_nalus" && n != "black_hole"
-                && n != "ip_family") {
+                && n != "ip_family" && n != "api_as_candidates") {
                 return srs_error_new(ERROR_SYSTEM_CONFIG_INVALID, "illegal rtc_server.%s", n.c_str());
             }
         }
@@ -3544,6 +3544,23 @@ std::string SrsConfig::get_rtc_server_candidates()
     return conf->arg0();
 }
 
+bool SrsConfig::get_api_as_candidates()
+{
+    static bool DEFAULT = true;
+
+    SrsConfDirective* conf = root->get("rtc_server");
+    if (!conf) {
+        return DEFAULT;
+    }
+
+    conf = conf->get("api_as_candidates");
+    if (!conf || conf->arg0().empty()) {
+        return DEFAULT;
+    }
+
+    return SRS_CONF_PERFER_TRUE(conf->arg0());
+}
+
 std::string SrsConfig::get_rtc_server_ip_family()
 {
     static string DEFAULT = "ipv4";
diff --git a/trunk/src/app/srs_app_config.hpp b/trunk/src/app/srs_app_config.hpp
index 51510b5df..a37461643 100644
--- a/trunk/src/app/srs_app_config.hpp
+++ b/trunk/src/app/srs_app_config.hpp
@@ -469,6 +469,7 @@ public:
     virtual bool get_rtc_server_enabled(SrsConfDirective* conf);
     virtual int get_rtc_server_listen();
     virtual std::string get_rtc_server_candidates();
+    virtual bool get_api_as_candidates();
     virtual std::string get_rtc_server_ip_family();
     virtual bool get_rtc_server_ecdsa();
     virtual bool get_rtc_server_encrypt();
diff --git a/trunk/src/app/srs_app_rtc_api.cpp b/trunk/src/app/srs_app_rtc_api.cpp
index b64595c79..e9593ca90 100644
--- a/trunk/src/app/srs_app_rtc_api.cpp
+++ b/trunk/src/app/srs_app_rtc_api.cpp
@@ -117,6 +117,7 @@ srs_error_t SrsGoApiRtcPlay::do_serve_http(ISrsHttpResponseWriter* w, ISrsHttpMe
     // The RTC user config object.
     SrsRtcUserConfig ruc;
     ruc.req_->ip = clientip;
+    ruc.api_ = api;
 
     srs_parse_rtmp_url(streamurl, ruc.req_->tcUrl, ruc.req_->stream);
 
@@ -383,6 +384,7 @@ srs_error_t SrsGoApiRtcPublish::do_serve_http(ISrsHttpResponseWriter* w, ISrsHtt
     // The RTC user config object.
     SrsRtcUserConfig ruc;
     ruc.req_->ip = clientip;
+    ruc.api_ = api;
 
     srs_parse_rtmp_url(streamurl, ruc.req_->tcUrl, ruc.req_->stream);
 
diff --git a/trunk/src/app/srs_app_rtc_server.cpp b/trunk/src/app/srs_app_rtc_server.cpp
index 608245b3a..ab3584048 100644
--- a/trunk/src/app/srs_app_rtc_server.cpp
+++ b/trunk/src/app/srs_app_rtc_server.cpp
@@ -6,6 +6,7 @@
 
 #include <srs_app_rtc_server.hpp>
 
+#include <set>
 using namespace std;
 
 #include <srs_app_config.hpp>
@@ -149,18 +150,66 @@ bool srs_is_rtcp(const uint8_t* data, size_t len)
     return (len >= 12) && (data[0] & 0x80) && (data[1] >= 192 && data[1] <= 223);
 }
 
-static std::vector<std::string> get_candidate_ips()
+srs_error_t api_server_as_candidates(string api, set<string>& candidate_ips)
 {
-    std::vector<std::string> candidate_ips;
+    srs_error_t err = srs_success;
 
+    if (api.empty() || !_srs_config->get_api_as_candidates()) {
+        return err;
+    }
+
+    SrsHttpUri uri;
+    if ((err = uri.initialize(api)) != srs_success) {
+        return srs_error_wrap(err, "parse %s", api.c_str());
+    }
+
+    string hostname = uri.get_host();
+    if (hostname.empty() || hostname == SRS_CONSTS_LOCALHOST_NAME) {
+        return err;
+    }
+    if (hostname == SRS_CONSTS_LOCALHOST || hostname == SRS_CONSTS_LOOPBACK || hostname == SRS_CONSTS_LOOPBACK6) {
+        return err;
+    }
+
+    // Try to parse the domain name if not IP.
+    int family = 0;
+    string ip = srs_dns_resolve(hostname, family);
+    if (ip.empty() || ip == SRS_CONSTS_LOCALHOST || ip == SRS_CONSTS_LOOPBACK || ip == SRS_CONSTS_LOOPBACK6) {
+        return err;
+    }
+
+    // Try to add the original hostname and ip as candidates.
+    candidate_ips.insert(hostname);
+    candidate_ips.insert(ip);
+
+    return err;
+}
+
+static set<string> discover_candidates(SrsRtcUserConfig* ruc)
+{
+    srs_error_t err = srs_success;
+
+    // Try to discover the eip as candidate, specified by user.
+    set<string> candidate_ips;
+    if (!ruc->eip_.empty()) {
+        candidate_ips.insert(ruc->eip_);
+    }
+
+    // Try to discover from api of request, if api_as_candidates enabled.
+    if ((err = api_server_as_candidates(ruc->api_, candidate_ips)) != srs_success) {
+        srs_warn("ignore discovering ip from api %s, err %s", ruc->api_.c_str(), srs_error_summary(err).c_str());
+        srs_freep(err);
+    }
+
+    // If not * or 0.0.0.0, use the candidate as exposed IP.
     string candidate = _srs_config->get_rtc_server_candidates();
     if (candidate != "*" && candidate != "0.0.0.0") {
-        candidate_ips.push_back(candidate);
+        candidate_ips.insert(candidate);
         return candidate_ips;
     }
 
-    // For * or 0.0.0.0, auto discovery expose ip addresses.
-    std::vector<SrsIPAddress*>& ips = srs_get_local_ips();
+    // Discover from local network interface addresses.
+    vector<SrsIPAddress*>& ips = srs_get_local_ips();
     if (ips.empty()) {
         return candidate_ips;
     }
@@ -180,7 +229,7 @@ static std::vector<std::string> get_candidate_ips()
             continue;
         }
 
-        candidate_ips.push_back(ip->ip);
+        candidate_ips.insert(ip->ip);
         srs_trace("Best matched ip=%s, ifname=%s", ip->ip.c_str(), ip->ifname.c_str());
     }
 
@@ -195,7 +244,7 @@ static std::vector<std::string> get_candidate_ips()
             continue;
         }
 
-        candidate_ips.push_back(ip->ip);
+        candidate_ips.insert(ip->ip);
         srs_trace("No best matched, use first ip=%s, ifname=%s", ip->ip.c_str(), ip->ifname.c_str());
         return candidate_ips;
     }
@@ -203,7 +252,7 @@ static std::vector<std::string> get_candidate_ips()
     // We use the first one.
     if (candidate_ips.empty()) {
         SrsIPAddress* ip = ips[0];
-        candidate_ips.push_back(ip->ip);
+        candidate_ips.insert(ip->ip);
         srs_warn("No best matched, use first ip=%s, ifname=%s", ip->ip.c_str(), ip->ifname.c_str());
         return candidate_ips;
     }
@@ -524,19 +573,17 @@ srs_error_t SrsRtcServer::do_create_session(SrsRtcUserConfig* ruc, SrsSdp& local
     local_sdp.set_fingerprint(_srs_rtc_dtls_certificate->get_fingerprint());
 
     // We allows to mock the eip of server.
-    if (!ruc->eip_.empty()) {
-        string host;
-        int port = _srs_config->get_rtc_server_listen();
-        srs_parse_hostport(ruc->eip_, host, port);
-
-        local_sdp.add_candidate(host, port, "host");
-        srs_trace("RTC: Use candidate mock_eip %s as %s:%d", ruc->eip_.c_str(), host.c_str(), port);
-    } else {
-        std::vector<string> candidate_ips = get_candidate_ips();
-        for (int i = 0; i < (int)candidate_ips.size(); ++i) {
-            local_sdp.add_candidate(candidate_ips[i], _srs_config->get_rtc_server_listen(), "host");
+    if (true) {
+        int listen_port = _srs_config->get_rtc_server_listen();
+        set<string> candidates = discover_candidates(ruc);
+        for (set<string>::iterator it = candidates.begin(); it != candidates.end(); ++it) {
+            string hostname; int port = listen_port;
+            srs_parse_hostport(*it, hostname,port);
+            local_sdp.add_candidate(hostname, port, "host");
         }
-        srs_trace("RTC: Use candidates %s", srs_join_vector_string(candidate_ips, ", ").c_str());
+
+        vector<string> v = vector<string>(candidates.begin(), candidates.end());
+        srs_trace("RTC: Use candidates %s", srs_join_vector_string(v, ", ").c_str());
     }
 
     // Setup the negotiate DTLS by config.
diff --git a/trunk/src/app/srs_app_rtc_server.hpp b/trunk/src/app/srs_app_rtc_server.hpp
index 8d3343a28..f16530df9 100644
--- a/trunk/src/app/srs_app_rtc_server.hpp
+++ b/trunk/src/app/srs_app_rtc_server.hpp
@@ -78,6 +78,7 @@ public:
     SrsSdp remote_sdp_;
     std::string eip_;
     std::string codec_;
+    std::string api_;
 
     // Generated data.
     SrsRequest* req_;
diff --git a/trunk/src/core/srs_core_version4.hpp b/trunk/src/core/srs_core_version4.hpp
index 9238cb913..5c2a4e8d1 100644
--- a/trunk/src/core/srs_core_version4.hpp
+++ b/trunk/src/core/srs_core_version4.hpp
@@ -9,6 +9,6 @@
 
 #define VERSION_MAJOR       4
 #define VERSION_MINOR       0
-#define VERSION_REVISION    217
+#define VERSION_REVISION    218
 
 #endif
diff --git a/trunk/src/kernel/srs_kernel_consts.hpp b/trunk/src/kernel/srs_kernel_consts.hpp
index ef87b5575..5cac4a4bc 100644
--- a/trunk/src/kernel/srs_kernel_consts.hpp
+++ b/trunk/src/kernel/srs_kernel_consts.hpp
@@ -107,6 +107,7 @@
 ///////////////////////////////////////////////////////////
 #define SRS_CONSTS_NULL_FILE "/dev/null"
 #define SRS_CONSTS_LOCALHOST "127.0.0.1"
+#define SRS_CONSTS_LOCALHOST_NAME "localhost"
 #define SRS_CONSTS_LOOPBACK "0.0.0.0"
 #define SRS_CONSTS_LOOPBACK6 "::"