DDS Router invalid when the network is bad(or disconnected)

[luzw5]

Hello, I am using DDSRouter recently, but I encountered a problem. I configured dds router on both my server and client, but when the network condition is very bad（or disconnected）, sometimes ddsrouter will stop routing valid data. At this time, restart dds router on the client side, and the data can be transmitted again. I would like to ask what is the reason for this problem?

[juanlofer-eprosima]

Hi @luzw5

We will need to know more details to help you. What do you mean by "stop routing valid data"? What are the YAML configurations you are using? Is this connection through WAN or in a LAN?

Best regards

[luzw5]

Thank you for your reply, I will provide you with more information.

Robot1

version: v3.0    
builtin-topics:
  - name: robot_state
    type: FreeFleetData::RobotState

  - name: task_result
    type: TaskResult::ResultData

  - name: mode_request
    type: FreeFleetData::ModeRequest

  - name: path_request
    type: FreeFleetData::PathRequest

  - name: destination_request
    type: FreeFleetData::DestinationRequest

  - name: photo_task_request
    type: PhotoTask::PhotoTaskRequest

  - name: task_request
    type: TaskRequest::RequestData
                                                
participants:

  - name: SimpleParticipant                                       
    kind: local                                                  
    domain: 44                                                  

  - name: echo_participantD1 
    kind: echo
    data: true             
    verbose: true    
    discovery: true  

  - name: WanParticipantD1                                   
    kind: wan                                               
    connection-addresses:                                   
      - domain: server
        port: 9010
        transport: tcp

Robot 2

version: v3.0 
builtin-topics:
  - name: robot_state
    type: FreeFleetData::RobotState

  - name: task_result
    type: TaskResult::ResultData

  - name: mode_request
    type: FreeFleetData::ModeRequest

  - name: path_request
    type: FreeFleetData::PathRequest

  - name: destination_request
    type: FreeFleetData::DestinationRequest

  - name: photo_task_request
    type: PhotoTask::PhotoTaskRequest

  - name: task_request
    type: TaskRequest::RequestData
                                                   
participants:

  - name: SimpleParticipant                                       
    kind: local                                                  
    domain: 42                                                  

  - name: echo_participantD1 
    kind: echo
    data: true             
    verbose: true    
    discovery: true  

  - name: WanParticipantD1                                   
    kind: wan                                               
    connection-addresses:                                   
      - domain: server
        port: 9017
        transport: tcp

Server

version: v3.0                                                    
builtin-topics:
  - name: robot_state
    type: FreeFleetData::RobotState

  - name: task_result
    type: TaskResult::ResultData

  - name: mode_request
    type: FreeFleetData::ModeRequest

  - name: path_request
    type: FreeFleetData::PathRequest

  - name: destination_request
    type: FreeFleetData::DestinationRequest

  - name: photo_task_request
    type: PhotoTask::PhotoTaskRequest

  - name: task_request
    type: TaskRequest::RequestData

participants:

  - name: ParticipantServer                                     
    kind: local                                                  
    domain: 4                                                   

  - name: EchoParticipantServer                                          
    kind: echo                                                       
    discovery: true                                                  
    data: true                                                       
    verbose: true                                                    

  - name: WanParticipantServerD1                                          
    kind: wan                                                  
    listening-addresses:
      - ip: 10.164.24.239                                           
        port: 9010                                              
        transport: tcp                                        

  - name: WanParticipantServerD2                            
    kind: wan                                            
    listening-addresses:
      - ip: 10.164.24.239                                       
        port: 9017                                          
        transport: tcp 

[luzw5]

The specific phenomenon is that when the network is not good, the DDS data sent by the Server can no longer be transmitted to Robot1 or Robot2. However, when I restart the docker container of Robot1 or Robot2, that is, re-run the ddsrouter program, it works normally again. Sorry, I'm not sure what's causing it. Could you please provide me with some debugging methods?

[juanlofer-eprosima]

Thank you! A couple more questions and suggestions for you to try:

• By looking at your diagram, I interpret that you have 3 different machines (2 robots and a server), and a docker container is run in each of them. Then you are using host's network stack (--net=host) to communicate within your LAN (or WAN? That IP address looks public). Am I right?
• This looks like a transport issue to me. UDP transport usually outperforms TCP, and we always recommend to use it whenever that's an option. I believe that's the case for your scenario if I'm not mistaken, could you please try with UDP?
• If you wish to communicate both clients through the server, it would be enough to have a WAN repeater participant in the server instead of two. Please have a look at Repeater DDS Router for more information.

[luzw5]

I think I can try to modify qos and udp now to solve my current problem. In addition, if I don't want the two robots to communicate directly, is my current configuration valid?

[juanlofer-eprosima]

With your configuration the two robots should not communicate directly, but through the server. What I meant is that there is no need of having two WAN participants in the server's router, and connect each of them with a different robot. You can connect the two robots to a WAN repeater participant in the server, and both will still be able to communicate (indirectly, through the server).

If you wish not to have any communication between the robots, then you would also need to connect both to the same WAN participant in the server's router, but this time configured with repeater: false.