FB_ClientDataExcha

In the event of an rising edge at the bExecute input, a null-terminated string is sent to the remote server, and a string returned by the remote server is read. The function block will try reading the data until null termination was detected in the string received. If the PLCPRJ_RECEIVE_TIMEOUT time-out period is exceeded or if an error occurs, reception is aborted. Data are attempted to be read again after a certain delay time, if no new data could be read during the last read attempt. This reduces the system load.

FUNCTION_BLOCK FB_ClientDataExcha
VAR_INPUT
    hSocket     : T_HSOCKET;
    sToServer   : T_MaxString;
    bExecute    : BOOL;
END_VAR
VAR_OUTPUT
    bBusy       : BOOL;
    bError      : BOOL;
    nErrId      : UDINT;
    sFromServer : T_MaxString;
END_VAR
VAR
    fbSocketSend : FB_SocketSend := ( sSrvNetID := '', tTimeout := DEFAULT_ADS_TIMEOUT );
    fbSocketReceive : FB_SocketReceive := ( sSrvNetID := '', tTimeout := DEFAULT_ADS_TIMEOUT );
    fbReceiveTON : TON;
    fbDisconnectTON : TON;
    RisingEdge : R_TRIG;
    eStep     : E_DataExchaSteps;
    cbReceived, startPos, endPos, idx : UDINT;
    cbFrame     : UDINT;
    rxBuffer    : ARRAY[0..MAX_PLCPRJ_RXBUFFER_SIZE] OF BYTE;
END_VAR

RisingEdge( CLK := bExecute );
CASE eStep OF
    DATAEXCHA_STATE_IDLE:
        IF RisingEdge.Q THEN
            bBusy := TRUE;
            bError := FALSE;
            nErrid := 0;
            cbReceived := 0;
            fbReceiveTON( IN := FALSE, PT := T#0s ); (* don't wait, read the first answer data immediately *)
            fbDisconnectTON( IN := FALSE, PT := T#0s );(* disable timeout check first *)
            eStep := DATAEXCHA_STATE_SEND_START;
        END_IF

    DATAEXCHA_STATE_SEND_START:
        fbSocketSend( bExecute := FALSE );
        fbSocketSend( hSocket := hSocket,
                pSrc := ADR( sToServer ),
                cbLen := LEN( sToServer ) + 1,(* string length inclusive zero delimiter *)
                bExecute:= TRUE );
        eStep := DATAEXCHA_STATE_SEND_WAIT;

    DATAEXCHA_STATE_SEND_WAIT:
        fbSocketSend( bExecute := FALSE );
        IF NOT fbSocketSend.bBusy THEN
            IF NOT fbSocketSend.bError THEN
                eStep := DATAEXCHA_STATE_RECEIVE_START;
            ELSE
                     LogError( 'FB_SocketSend (local client)', fbSocketSend.nErrId );
                nErrId := fbSocketSend.nErrId;
                eStep := DATAEXCHA_STATE_ERROR;
            END_IF
        END_IF

    DATAEXCHA_STATE_RECEIVE_START:
        fbDisconnectTON( );
        fbReceiveTON( IN := TRUE );
        IF fbReceiveTON.Q THEN
            fbReceiveTON( IN := FALSE );
            fbSocketReceive( bExecute := FALSE );
            fbSocketReceive( hSocket:= hSocket,
                    pDest:= ADR( rxBuffer ) + cbReceived,
                    cbLen:= SIZEOF( rxBuffer ) - cbReceived,
                    bExecute:= TRUE );
            eStep := DATAEXCHA_STATE_RECEIVE_WAIT;
        END_IF

    DATAEXCHA_STATE_RECEIVE_WAIT:
        fbSocketReceive( bExecute := FALSE );
        IF NOT fbSocketReceive.bBusy THEN
            IF NOT fbSocketReceive.bError THEN
                     IF (fbSocketReceive.nRecBytes > 0) THEN(* bytes received *)
                    startPos        := cbReceived;(* rxBuffer array index of first data byte *)
                    endPos         := cbReceived + fbSocketReceive.nRecBytes - 1;(* rxBuffer array index of last data byte *)
                    cbReceived := cbReceived + fbSocketReceive.nRecBytes;(* calculate the number of received data bytes *)
                    cbFrame     := 0;(* reset frame length *)
                    IF cbReceived < SIZEOF( sFromServer ) THEN(* no overflow *)
                        fbReceiveTON( PT := T#0s ); (* bytes received => increase the read (polling) speed *)
                        fbDisconnectTON( IN := FALSE );(* bytes received => disable timeout check *)
                        (* search for string end delimiter *)
                        FOR idx := startPos TO endPos BY 1 DO
                                    IF rxBuffer[idx] = 0 THEN(* string end delimiter found *)
                                cbFrame := idx + 1;(* calculate the length of the received string (inclusive the end delimiter) *)
                                MEMCPY( ADR( sFromServer ), ADR( rxBuffer ), cbFrame );(* copy the received string to the output variable (inclusive the end delimiter) *)
                                MEMMOVE( ADR( rxBuffer ), ADR( rxBuffer[cbFrame] ), cbReceived - cbFrame );(* move the reamaining data bytes *)
                                cbReceived := cbReceived - cbFrame;(* recalculate the remaining data byte length *)
                                bBusy := FALSE;
                                eStep := DATAEXCHA_STATE_IDLE;
                                EXIT;
                                    END_IF
                        END_FOR
                    ELSE(* there is no more free read buffer space => the answer string should be terminated *)
                        LogError( 'FB_SocketReceive (local client)', PLCPRJ_ERROR_RECEIVE_BUFFER_OVERFLOW );
                        nErrId := PLCPRJ_ERROR_RECEIVE_BUFFER_OVERFLOW;(* buffer overflow !*)
                        eStep := DATAEXCHA_STATE_ERROR;
                    END_IF
                ELSE(* no bytes received *)
                    fbReceiveTON( PT := PLCPRJ_RECEIVE_POLLING_TIME );(* no bytes received => decrease the read (polling) speed *)
                    fbDisconnectTON( IN := TRUE, PT := PLCPRJ_RECEIVE_TIMEOUT );(* no bytes received => enable timeout check*)
                    IF fbDisconnectTON.Q THEN (* timeout error*)
                               fbDisconnectTON( IN := FALSE );
                        LogError( 'FB_SocketReceive (local client)', PLCPRJ_ERROR_RECEIVE_TIMEOUT );
                        nErrID := PLCPRJ_ERROR_RECEIVE_TIMEOUT;
                        eStep := DATAEXCHA_STATE_ERROR;
                    ELSE(* repeat reading *)
                        eStep := DATAEXCHA_STATE_RECEIVE_START; (* repeat reading *)
                    END_IF
                END_IF
            ELSE(* receive error *)
                LogError( 'FB_SocketReceive (local client)', fbSocketReceive.nErrId );
                nErrId := fbSocketReceive.nErrId;
                eStep := DATAEXCHA_STATE_ERROR;
            END_IF
           END_IF

    DATAEXCHA_STATE_ERROR:(* error step *)
        bBusy := FALSE;
        bError := TRUE;
        cbReceived := 0;
        eStep := DATAEXCHA_STATE_IDLE;
END_CASE