Question about EthernetKRL

Hello,

I'm working on a project where it's necessary to communicate between Main Control Unit (Just a PC) and KUKA KRC4. For that, Ethernet KRL 2.2 (for KRC4 8.3) package was chosen. Provided EthernetKRL documentation is quite brief, but enough to understand and ensure basic communication.

My task involves quite intensive communication where MCU acts as server and robot as client. Lets say I have 10 different queries, some of them use binary stream, some XML data option. I use binary stream when robot asks server about some information\data availability (and server request: yes or no). If data\information is available robot reconnects with different configuration file and receives data as XML structure. The difficulty lies in the fact that some requests must occur in parallel, independent of each other, because the requests calls happen in different submits (yeah, multisubmit module). Right now, this system is implemented in the following way -> I have separate sub ("Networking_manager.sub" ;)) which cycles all possible request, checks if this particular type of request is active (they can be activated from different subs), and if it is -> creates connection with proper configuration file, sends request, receives answer from server -> deactivates request ->move to next request type. So, robot constantly bombards the server with requests. Some times it works, but sometimes I receive errors about lost connection. Even if every RET variable returns 0 as result. And so, based on all the information above:

1. Is it possible to create multiple simultaneous connections from robot to server with EthernetKRL? This would solve the problem like a charm. Documentation states ("...The number of active connections is limited to 16."), but I didn't managed to test is successfully.

2. In my mind, there is another implementation option. Just make large single request which will contain all smaller requests with their status (active\inactive) and all "answer" data. So robot and MCU can just ping pong this single large data butch, changing necessary parts of it to communicate. Is it good option from your opinion?

3. How would you implement such communication with Ethernet KRL?

Thanks in advance!

Quote

If i recall correctly Ethernet KRL allows only one server (on the robot side). But in your case server is external, so robot is acting as client. That means (as long as your server support it) you can create several connection to it, either from same or from different robots.

I'm using src modules to test things first, so sub modules were mentioned to give explanation of planned end system. I have written simple src module which tries to create two simultaneous connections from robot to server. Server is 100% capable to work with multiple connection form single client. Here is src module code:

DEF  multi_tcp_connection ( )
    INT i
    DECL EKI_STATUS RET1
    DECL EKI_STATUS RET2
    DECL CHAR inquiry1[64]
    DECL CHAR inquiry2[64]

    INTERRUPT DECL 89 WHEN $FLAG[1] == TRUE DO GET_FIRST_DATA()
    INTERRUPT DECL 90 WHEN $FLAG[2] == TRUE DO GET_SECOND_DATA()
    INTERRUPT ON 89
    INTERRUPT ON 90

    FOR i=1 TO 64 STEP 1
      inquiry1[i]=0
      inquiry2[i]=0
    ENDFOR
    
    RET1=EKI_Init("Call_to_server1")
    RET2=EKI_Init("Call_to_server2")
    RET1=EKI_Open("Call_to_server1")
    RET2=EKI_Open("Call_to_server2")
    WAIT SEC 0
    
    inquiry1[] = "1 connection test"
    inquiry2[] = "2 connection test"
    $FLAG[1] = FALSE
    $FLAG[2] = FALSE
    RET1=EKI_Send("Call_to_server1", inquiry1[])
    RET2=EKI_Send("Call_to_server2", inquiry2[])
    $FLAG[89] = FALSE
    $FLAG[90] = FALSE
    WAIT SEC 0
    
    WAIT FOR $FLAG[89] AND $FLAG[90]
    
    
    RET1=EKI_Close("Call_to_server")
    RET1=EKI_Clear("Call_to_server")
    RET2=EKI_Close("Call_to_server")
    RET2=EKI_Clear("Call_to_server")
END

DEF GET_FIRST_DATA()
    DECL EKI_STATUS RET
    DECL INT i
    FOR i=1 TO 64 STEP 1
       echo1[i]=0
    ENDFOR
    RET = EKI_GetString("Call_to_server1", "BufferIn1", echo1[])
    $FLAG[89] = TRUE
    $FLAG[1] = FALSE
END

DEF GET_SECOND_DATA()
    DECL EKI_STATUS RET
    DECL INT i
    FOR i=1 TO 64 STEP 1
       echo2[i]=0
    ENDFOR
    RET = EKI_GetString("Call_to_server2", "BufferIn2", echo2[])
    $FLAG[90] = TRUE
    $FLAG[2] = FALSE
END

Here is "Call_to_server1.xml" internals:

<ETHERNETKRL>
    <CONFIGURATION>
        <EXTERNAL>
            <IP>172.31.1.140</IP>
            <PORT>59152</PORT>
            <TYPE>Server</TYPE>
        </EXTERNAL>
    </CONFIGURATION>
    <RECEIVE>
        <RAW>
            <ELEMENT Tag="BufferIn1" Type="STREAM" Set_Flag="1" EOS="10"/>
        </RAW>
    </RECEIVE>
    <SEND>
        <RAW>
            <ELEMENT Tag="BufferOut1" Type="STREAM" EOS="10" />
        </RAW>
    </SEND>
</ETHERNETKRL>

The difference between "Call_to_server1" and "Call_to_server2" are receive flag number (1 or 2) and different names for input and output buffers (with indices 1 or 2). External configuration contains right server connection parameters and they are the same for both configuration files.

Considering basics of TCP\IP protocol, a connection or "socket" on server side is defined by combination of "Server IP, Server Port, Client IP, Client Port". So any other connection to the same server will have ether different Client IP or Client Port. The Client IP will be the same coz we are connection from the same robot. According to EthernetKRL documentation, we do not have access to port choice if KLI is acting as client, so, I suppose EthernetKRL package manages ports itself. So, in theory, my test program must work. But code gives EKI00023 error at line:

RET2=EKI_Init("Call_to_server2")

what means that - "The Ethernet connection has already been initialized with the function EKI_Init()." And documentation advices me to close active connection before creating new....

Either, I'm doing something wrong, or it is not possible to make several simultaneous connections from single robot to the same server, even if documentation states it is possible.

Quote from SkyeFire

I'm pretty sure that parallel connections require separate ports for deconfliction.

Also, in my experience (which is a few versions old now), opening and closing connections rapidly tends to cause errors. You might be better off creating some persistent connections and simply use some error trapping to delete and re-open the connection if/when there's a failure.

I found a problem. Was not related to software part at all, a switch I used to create LAN network was guilty. So, now I can create up to 16 simultaneous connections as it stated in documentation.

SkyeFire, how error trapping can be implemented? Through EKI_STATUS value control?

Quote from haris.bukhari

Hi Danii
I am going to work on a project involving simple communication between the KRC and a PC/Laptop. The configuration we are going to use is KRC as server and PC as client. Data exchange will be binary. Is there any update on your project and is there anything that I must look out for?

We are using xml data exchange option. Much much simpler, because xml allows to parse data with ease, for both, KRC and external PC. Of course it depends on amount and type of data you would like to send/receive. So SkyeFire asked right questions!