diff --git a/trunk/src/app/srs_app_rtc_conn.cpp b/trunk/src/app/srs_app_rtc_conn.cpp
index e8963a213..f21fd247b 100644
--- a/trunk/src/app/srs_app_rtc_conn.cpp
+++ b/trunk/src/app/srs_app_rtc_conn.cpp
@@ -606,21 +606,9 @@ void SrsRtcSenderThread::send_and_free_messages(SrsSharedPtrMessage** msgs, int
         srs_freep(msg);
     }
 
-
-    if (!mhdrs.empty()) {
-        mmsghdr* msgvec = &mhdrs[0];
-        unsigned int vlen = (unsigned int)mhdrs.size();
-        int r0 = srs_sendmmsg(udp_mux_skt->stfd(), msgvec, vlen, 0, SRS_UTIME_NO_TIMEOUT);
-        if (r0 != (int)vlen) {
-            srs_warn("sendmsg %d msgs, %d done", vlen, r0);
-        }
-    }
-    for (int i = 0; i < (int)mhdrs.size(); i++) {
-        msghdr* hdr = &mhdrs[i].msg_hdr;
-        for (int i = 0; i < (int)hdr->msg_iovlen; i++) {
-            iovec* iov = hdr->msg_iov + i;
-            delete (char*)iov->iov_base;
-        }
+    if ((err = rtc_session->rtc_server->send_and_free_messages(udp_mux_skt->stfd(), mhdrs)) != srs_success) {
+        srs_warn("sendmsg %d msgs, err %s", mhdrs.size(), srs_error_summary(err).c_str());
+        srs_freep(err);
     }
 }
 
@@ -1072,12 +1060,21 @@ SrsRtcServer::SrsRtcServer()
 {
     listener = NULL;
     timer = new SrsHourGlass(this, 1 * SRS_UTIME_SECONDS);
+
+    mmstfd = NULL;
+    waiting_msgs = false;
+    cond = srs_cond_new();
+    trd = new SrsDummyCoroutine();
 }
 
 SrsRtcServer::~SrsRtcServer()
 {
     srs_freep(listener);
     srs_freep(timer);
+
+    srs_freep(trd);
+    srs_cond_destroy(cond);
+    clear();
 }
 
 srs_error_t SrsRtcServer::initialize()
@@ -1092,6 +1089,12 @@ srs_error_t SrsRtcServer::initialize()
         return srs_error_wrap(err, "start timer");
     }
 
+    srs_freep(trd);
+    trd = new SrsSTCoroutine("udp", this);
+    if ((err = trd->start()) != srs_success) {
+        return srs_error_wrap(err, "start coroutine");
+    }
+
     return err;
 }
 
@@ -1304,6 +1307,80 @@ srs_error_t SrsRtcServer::notify(int type, srs_utime_t interval, srs_utime_t tic
     return srs_success;
 }
 
+srs_error_t SrsRtcServer::send_and_free_messages(srs_netfd_t stfd, const vector<mmsghdr>& msgs)
+{
+    srs_error_t err = srs_success;
+
+    mmstfd = stfd;
+    mmhdrs.insert(mmhdrs.end(), msgs.begin(), msgs.end());
+
+    if (waiting_msgs) {
+        waiting_msgs = false;
+        srs_cond_signal(cond);
+    }
+
+    return err;
+}
+
+void SrsRtcServer::clear()
+{
+    for (int i = 0; i < (int)mmhdrs.size(); i++) {
+        msghdr* hdr = &mmhdrs[i].msg_hdr;
+        for (int i = 0; i < (int)hdr->msg_iovlen; i++) {
+            iovec* iov = hdr->msg_iov + i;
+            delete (char*)iov->iov_base;
+        }
+    }
+
+    mmhdrs.clear();
+}
+
+srs_error_t SrsRtcServer::cycle()
+{
+    srs_error_t err = srs_success;
+
+    // TODO: FIXME: Use pithy print.
+    uint32_t cnt = 1;
+
+    while (true) {
+        if ((err = trd->pull()) != srs_success) {
+            return err;
+        }
+
+        // TODO: FIXME: Use cond trigger.
+        if (mmhdrs.empty()) {
+            waiting_msgs = true;
+            srs_cond_wait(cond);
+        }
+
+        vector<mmsghdr> mhdrs = mmhdrs;
+        mmhdrs.clear();
+
+        // TODO: FIXME: Use pithy print.
+        if ((cnt++ % 1000) == 0) {
+            srs_trace("SEND %d msgs by sendmmsg", mhdrs.size());
+        }
+
+        if (!mhdrs.empty()) {
+            mmsghdr* msgvec = &mhdrs[0];
+            unsigned int vlen = (unsigned int)mhdrs.size();
+            int r0 = srs_sendmmsg(mmstfd, msgvec, vlen, 0, SRS_UTIME_NO_TIMEOUT);
+            if (r0 != (int)vlen) {
+                srs_warn("sendmsg %d msgs, %d done", vlen, r0);
+            }
+        }
+        for (int i = 0; i < (int)mhdrs.size(); i++) {
+            msghdr* hdr = &mhdrs[i].msg_hdr;
+            for (int i = 0; i < (int)hdr->msg_iovlen; i++) {
+                iovec* iov = hdr->msg_iov + i;
+                delete (char*)iov->iov_base;
+            }
+        }
+    }
+
+    return err;
+}
+
 RtcServerAdapter::RtcServerAdapter()
 {
     rtc = new SrsRtcServer();
diff --git a/trunk/src/app/srs_app_rtc_conn.hpp b/trunk/src/app/srs_app_rtc_conn.hpp
index 49c054174..8746653d1 100644
--- a/trunk/src/app/srs_app_rtc_conn.hpp
+++ b/trunk/src/app/srs_app_rtc_conn.hpp
@@ -36,6 +36,7 @@
 #include <string>
 #include <map>
 #include <vector>
+#include <sys/socket.h>
 
 #include <openssl/ssl.h>
 #include <srtp2/srtp.h>
@@ -205,11 +206,18 @@ private:
     srs_error_t on_rtcp_receiver_report(char* buf, int nb_buf, SrsUdpMuxSocket* udp_mux_skt);
 };
 
-class SrsRtcServer : virtual public ISrsUdpMuxHandler, virtual public ISrsHourGlass
+class SrsRtcServer : virtual public ISrsUdpMuxHandler, virtual public ISrsHourGlass, virtual public ISrsCoroutineHandler
 {
 private:
     SrsUdpMuxListener* listener;
     SrsHourGlass* timer;
+private:
+    SrsCoroutine* trd;
+    srs_cond_t cond;
+    bool waiting_msgs;
+    // TODO: FIXME: Support multiple stfd.
+    srs_netfd_t mmstfd;
+    std::vector<mmsghdr> mmhdrs;
 private:
     std::map<std::string, SrsRtcSession*> map_username_session; // key: username(local_ufrag + ":" + remote_ufrag)
     std::map<std::string, SrsRtcSession*> map_id_session; // key: peerip(ip + ":" + port)
@@ -238,6 +246,11 @@ private:
 // interface ISrsHourGlass
 public:
     virtual srs_error_t notify(int type, srs_utime_t interval, srs_utime_t tick);
+// Internal only.
+public:
+    srs_error_t send_and_free_messages(srs_netfd_t stfd, const std::vector<mmsghdr>& msgs);
+    void clear();
+    virtual srs_error_t cycle();
 };
 
 // The RTC server adapter.