merge srs2, use specific error code for dns resolve

@@ -206,6 +206,7 @@ Please select your language:
 
 ### V2 changes
 
+* v2.0, 2017-01-18, fix [#750][bug #750] use specific error code for dns resolve. 2.0.231
 * <strong>v2.0, 2017-01-18, [2.0 beta4(2.0.230)][r2.0b4] released. 86334 lines.</strong>
 * v2.0, 2017-01-18, fix [#749][bug #749], timestamp overflow for ATC. 2.0.230
 * v2.0, 2017-01-11, fix [#740][bug #740], convert ts aac audio private stream 1 to common. 2.0.229

@@ -104,6 +104,7 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #define ERROR_SYSTEM_CONFIG_RAW_PARAMS      1063
 #define ERROR_SYSTEM_FILE_NOT_EXISTS        1064
 #define ERROR_SYSTEM_HOURGLASS_RESOLUTION   1065
+#define ERROR_SYSTEM_DNS_RESOLVE            1066
 
 ///////////////////////////////////////////////////////
 // RTMP protocol error.

@@ -491,7 +491,7 @@ int srs_librtmp_context_resolve_host(Context* context)
     // connect to server:port
     context->ip = srs_dns_resolve(context->host);
     if (context->ip.empty()) {
-        return -1;
+        return ERROR_SYSTEM_DNS_RESOLVE;
     }
     
     return ret;