diff --git a/api/source/mk_common.cpp b/api/source/mk_common.cpp
index 0430e685..1604af61 100644
--- a/api/source/mk_common.cpp
+++ b/api/source/mk_common.cpp
@@ -308,7 +308,7 @@ API_EXPORT void API_CALL mk_webrtc_get_answer_sdp2(void *user_data, on_user_data
     WebRtcPluginManager::Instance().getAnswerSdp(*session, type, WebRtcArgsUrl(url),
                                                  [offer_str, session, ptr, cb](const WebRtcInterface &exchanger) mutable {
         try {
-            auto sdp_answer = const_cast<WebRtcInterface &>(exchanger).getAnswerSdp(offer_str);
+            auto sdp_answer = exchangeSdp(exchanger, offer_str);
             cb(ptr.get(), sdp_answer.data(), nullptr);
         } catch (std::exception &ex) {
             cb(ptr.get(), nullptr, ex.what());
diff --git a/server/WebApi.cpp b/server/WebApi.cpp
index 18056a10..89abf584 100755
--- a/server/WebApi.cpp
+++ b/server/WebApi.cpp
@@ -1604,7 +1604,7 @@ void installWebApi() {
             headerOut["Access-Control-Allow-Origin"] = "*";
 
             try {
-                val["sdp"] = const_cast<WebRtcInterface &>(exchanger).getAnswerSdp(offer);
+                val["sdp"] = exchangeSdp(exchanger, offer);
                 val["id"] = exchanger.getIdentifier();
                 val["type"] = "answer";
                 invoker(200, headerOut, val.toStyledString());
@@ -1628,7 +1628,7 @@ void installWebApi() {
                 try {
                     // 设置返回类型
                     headerOut["Content-Type"] = "application/sdp";
-                    invoker(201, headerOut, const_cast<WebRtcInterface &>(exchanger).getAnswerSdp(offer));
+                    invoker(201, headerOut, exchangeSdp(exchanger, offer));
                 } catch (std::exception &ex) {
                     headerOut["Content-Type"] = "text/plain";
                     invoker(406, headerOut, ex.what());
diff --git a/webrtc/WebRtcTransport.cpp b/webrtc/WebRtcTransport.cpp
index 347f870c..dae2f533 100644
--- a/webrtc/WebRtcTransport.cpp
+++ b/webrtc/WebRtcTransport.cpp
@@ -1131,6 +1131,10 @@ void WebRtcPluginManager::registerPlugin(const string &type, Plugin cb) {
     _map_creator[type] = std::move(cb);
 }
 
+std::string exchangeSdp(const WebRtcInterface &exchanger, const std::string& offer) {
+    return const_cast<WebRtcInterface &>(exchanger).getAnswerSdp(offer);
+}
+
 void WebRtcPluginManager::getAnswerSdp(Session &sender, const string &type, const WebRtcArgs &args, const onCreateRtc &cb) {
     lock_guard<mutex> lck(_mtx_creator);
     auto it = _map_creator.find(type);
diff --git a/webrtc/WebRtcTransport.h b/webrtc/WebRtcTransport.h
index dfae8012..eb33b090 100644
--- a/webrtc/WebRtcTransport.h
+++ b/webrtc/WebRtcTransport.h
@@ -43,6 +43,8 @@ public:
     virtual const std::string &getIdentifier() const = 0;
 };
 
+std::string exchangeSdp(const WebRtcInterface &exchanger, const std::string& offer);
+
 class WebRtcException : public WebRtcInterface {
 public:
     WebRtcException(const SockException &ex) : _ex(ex) {};