diff --git a/server/src/UdpServer.cs b/server/src/UdpServer.cs
index 44fe26b..8489f3d 100644
--- a/server/src/UdpServer.cs
+++ b/server/src/UdpServer.cs
@@ -162,7 +162,7 @@ public class UDPServer
             isTimeout = timeleft >= TimeSpan.FromMilliseconds(timeout);
         }
 
-        if (data == null)
+        if (data is null)
         {
             logger.Trace("Get nothing even after time out");
             return Optional.None<UDPData>();
@@ -194,6 +194,8 @@ public class UDPServer
                 if (udpData.ContainsKey(ipAddr))
                 {
                     data = udpData[ipAddr];
+                    logger.Debug($"Find UDP Data Array: {data.ToString()}");
+                    break;
                 }
             }
 
@@ -201,8 +203,9 @@ public class UDPServer
             isTimeout = timeleft >= TimeSpan.FromMilliseconds(timeout);
         }
 
-        if (data == null)
+        if (data is null)
         {
+            logger.Trace("Get nothing even after time out");
             return Optional.None<List<UDPData>>();
         }
         else