For #1638, #307, use short-term http connection for rtc to use new cid.

trunk/src/app/srs_app_http_api.cpp

@@ -799,6 +799,10 @@ srs_error_t SrsGoApiSdp::serve_http(ISrsHttpResponseWriter* w, ISrsHttpMessage*
     // path: {pattern}
     // method: POST
     // e.g. /api/v1/sdp/ args = json:{"sdp":"sdp...", "app":"webrtc", "stream":"test"}
+
+    // For each RTC session, we use short-term HTTP connection.
+    SrsHttpHeader* hdr = w->header();
+    hdr->set("Connection", "Close");
     
     string req_json;
     if ((err = r->body_read_all(req_json)) != srs_success) {

trunk/src/service/srs_service_http_conn.cpp

@@ -907,7 +907,9 @@ srs_error_t SrsHttpResponseWriter::send_header(char* data, int size)
     }
     
     // keep alive to make vlc happy.
-    hdr->set("Connection", "Keep-Alive");
+    if (hdr->get("Connection").empty()) {
+        hdr->set("Connection", "Keep-Alive");
+    }
 
     // Filter the header before writing it.
     if (hf && ((err = hf->filter(hdr)) != srs_success)) {