TCP/IP disconnect not handled correctly

jeroen

Hi,
 
I have a TCP/IP connection between my robot to a control program running on a PC. The code below runs in a separate semi-static task.
If I physically disconnect the robot (plug out cable), after a while this task crashes on the SocketSend function call shown below.
The socket_status keeps reporting SOCKET_CONNECTED however.
How can I fix/work around this?
 
Regards,
 
! --------------------------------------------------------------------------------
! Send status to client.

! --------------------------------------------------------------------------------

TRAP TrapStatus

  VAR socketStatus sockStat;

  sockStat:=SocketGetStatus(client_socket);

  IF sockStat=SOCKET_CONNECTED THEN

    ! Send status to client.

    SocketSend client_socketStr:=Status+ByteToStr(13Char)+ByteToStr(10Char);

  ELSE

    ! Connection lost?

    ! ...

  ENDIF

  ! Acknowledge.

  SetDO doStatus,0;

  RETURN;

ERROR

  !TryNext;

  ! Acknowledge.

  SetDO doStatus,0;

  RETURN;

ENDTRAP

 

 

Henrik Berlin

Moved to RobotWare forum.

James_NC

I've been working through this myself, and I think I can help.  SOCKET_CONNECTED will be true unless the client or server explicitly closes the connection.  However, if the cable is unplugged, you should be getting a Timeout Error.  You can handle error with the following error catcher:

ERROR
    IF ERRNO=ERR_SOCK_TIMEOUT THEN
          ...

Just be careful not to spend too much time in your TRAP, as I believe code ignores any other interrupts while inside a TRAP.

lubosko105

Hallo jeroen.
In your topic I see you are writing TCP communication. I want to make TCP server on the server side. Do you know if is posible to start new thread with socket (returned by SocketAccept fnc) ? Your code looks working like this.
thanks for help.

jeroen

What exactly do you mean by a new thread?

I don't think you can make a server with a thread for each connection; you just have to handle all connections in the same task.

 

In my application I just need to handle a single connection.

 

I have a ServerStart procedure:

PROC ServerStart(bool Recover)
IF Recover THEN

  Log "ServerStart with recovery need";

  SocketClose server_socket;

  SocketClose client_socket;

ELSE

  Log "ServerStart without the need for recovery";

ENDIF

  SocketCreate server_socket;

  SocketBind server_socket, IPAddress, IPPort;

  SocketListen server_socket;

  Log "Wait for connection";

  SocketAccept server_socket, client_socketClientAddress:=client_ipTime:=WAIT_MAX;

  Log "Connection with " + client_ip;

ERROR

  IF ERRNO=ERR_SOCK_TIMEOUT THEN

    Log "ERR_SOCK_TIMEOUT";

    Retry;

  ELSEIF ERRNO=ERR_SOCK_CLOSED THEN

    Log "ERR_SOCK_CLOSED";

    Return;

ELSE

  Log "Unknown error"

ENDIF

ENDPROC

And in the main loop I handle the server like:

 

ServerStart(FALSE);

-- Some more initialization

WHILE TRUE DO
  SocketReceive client_socket Str:=ReceiveTime:=nHeartbeatTimeout;
  Log Receive;
  ! Process data
ENDWHILE
ERROR
  IF ERRNO=ERR_SOCK_TIMEOUT THEN
  Log "Timeout";
  ! Close connection and restart.
  ServerStart(TRUE);
  Retry;
ELSEIF ERRNO=ERR_SOCK_CLOSED THEN
  Log "Socket closed by peer!";
  ServerStart(TRUE);
  Retry;
ELSE
  Log "Unknown error";
ENDIF
ENDPROC

jeroen2012-01-26 15:22:43

niggos

Hi there!

I'm quiet new to RAPID, but I spent some time on developing

a TCP-based communication from client-PC to server-IRC5.

just a thought:

If you have the option "Multitasking" installed, you can use some additional tasks for separate server sockets that listen continously for incoming data.

@jeroen:

You can try to use 

ResetRetrycount;  

in your error handling rigth after 

ServerStart(TRUE);

The standard number of retry counts is 4 (configurable somewhere ...), so after four times of handling the same error, the 

Retry; 

will not be executed and the loop/proc will come to end/be finished.

hope this might help!?