ROSConnection.cs:854

[Yuanzizizi]

Describe the bug
connection fails

Console logs / stack traces
Connection to 172.23.24.185:10000 failed - System.NullReferenceException: Object reference not set to an instance of an object
  at Unity.Robotics.ROSTCPConnector.RosTopicState.OnConnectionEstablished (System.Net.Sockets.NetworkStream stream) [0x0005d] in C:\Users\MXH\test_objects_uav_1218\Library\PackageCache\com.unity.robotics.ros-tcp-connector@c27f00c6cf\Runtime\TcpConnector\RosTopicState.cs:260 
  at Unity.Robotics.ROSTCPConnector.ROSConnection.OnConnectionStartedCallback (System.Net.Sockets.NetworkStream stream) [0x00041] in C:\Users\MXH\test_objects_uav_1218\Library\PackageCache\com.unity.robotics.ros-tcp-connector@c27f00c6cf\Runtime\TcpConnector\ROSConnection.cs:531 
  at Unity.Robotics.ROSTCPConnector.ROSConnection+d__115.MoveNext () [0x0010c] in C:\Users\MXH\test_objects_uav_1218\Library\PackageCache\com.unity.robotics.ros-tcp-connector@c27f00c6cf\Runtime\TcpConnector\ROSConnection.cs:796 
UnityEngine.Debug:Log (object)
Unity.Robotics.ROSTCPConnector.ROSConnection/d__115:MoveNext () (at C:/Users/MXH/test_objects_uav_1218/Library/PackageCache/com.unity.robotics.ros-tcp-connector@c27f00c6cf/Runtime/TcpConnector/ROSConnection.cs:854)
System.Threading._ThreadPoolWaitCallback:PerformWaitCallback ()

Environment (please complete the following information, where applicable):

• Unity Version: [e.g. Unity 2020.3.48f1c1]