Problem with SysSockRecv function

2021-02-24T18:00:04.547000Z

did you able to send and receive data later ?

Problem with SysSockRecv function

2020-02-27T18:57:10.459000Z

Hello
Me again
Actually I have found where the problem came from. The code was ok but the format of the command I used was missing a new line character at the end (what was not said in the notice).
I have managed to see that using Wireshark a freeware that allows tcp frame inspection on the net. There I saw that the '0a' character was missing compared to the utility software provided by the manufacturer.
Though nobody answered I have thought It might be usefull to some of you to have a clue on how to debug this kind of problem.
Michel

Problem with SysSockRecv function

2020-02-27T18:57:09.042000Z

Hello,

I am running a wago PFC200 PLC and try to drive a equipment using ethernet TCP protocol under Codesys V2.3. I am able to create and connect a socket, send data and close the socket. Yet each time I want to receive data, that I know to be send by the equipment the connexion got stuck and I just have to switch on and of the equipment and restart my PLC.

When I check if the equipement is ready to send back data using SysSockSelect, it returns 0, meaning that it is not ready to talk although it does send data. If I don't use the SysSockSelect and go straight to SysSockRecv then the program got stuck.

Does anyone have an idea ?

Thank for your help.

Michel

PROGRAM PLC_PRG
VAR

sendBt:BOOL;
recvBT:BOOL;


strLec:STRING(100);
strEcr:STRING(100):=':FREQ:21.2345MHz';

openSocket:BOOL;
closeSocket:BOOL;


diSocket : DINT := -1;
iPort : INT:=9760;
stDestIPAddress : STRING := '192.168.9.47';

bySend : STRING(12) := ':IDN?';
byRecv : STRING(128);
xx:INT;
yy:DINT;
nbS:INT:=64;
nbR:INT:=128;

END_VAR

IF openSocket THEN
openSocket:=FALSE;
IF(diSocket=-1) THEN
diSocket := TcpClientOpenSocket(iPort, stDestIPAddress, 1000);
END_IF
END_IF

IF recvBt THEN
IF diSocket <> -1 THEN
TcpReceiveData(diSocket, ADR(byRecv), SIZEOF(byRecv), 2);
END_IF
recvBt:=FALSE;
END_IF

IF sendBt THEN
IF diSocket <> -1 THEN
TcpSendData(diSocket, ADR(bySend), SIZEOF(bySend), 2);
END_IF
sendBt:=FALSE;
END_IF

IF closeSocket THEN
closeSocket := FALSE;
SysSockClose(diSocket:=diSocket);
diSocket := -1;
END_IF

(*******)
FUNCTION TcpClientOpenSocket : DINT
( Open TCP client socket to connect to server.
Return: Socket-Id for connection session
)
VAR_INPUT
iPort:INT; ( Port number of TCP socket to open )
stIPAddress:STRING; ( IP-Address of server to connect to )
diMaxDataSize:DINT; ( Max size of data to transmitt; if size = 0 default values are used )
END_VAR
VAR
diSocket:DINT;
bOptNoDelay:BOOL;
lOptLinger:SOCKET_LINGER;
bResult:BOOL;
sa:SOCKADDRESS;
END_VAR

diSocket:=SysSockCreate(SOCKET_AF_INET, SOCKET_STREAM, 0);

IF diSocket <> SOCKET_INVALID THEN

SysSockSetOption(diSocket, SOCKET_SOL, SOCKET_SO_SNDBUF, ADR(diMaxDataSize), SIZEOF(diMaxDataSize));
SysSockSetOption(diSocket, SOCKET_SOL, SOCKET_SO_RCVBUF, ADR(diMaxDataSize), SIZEOF(diMaxDataSize));
lOptLinger.l_onoff:=0;
lOptLinger.l_linger:=0;
SysSockSetOption(diSocket,  SOCKET_SOL, SOCKET_SO_LINGER, ADR(lOptLinger), SIZEOF(lOptLinger));
bOptNoDelay:=TRUE;
SysSockSetOption(diSocket,  SOCKET_IPPROTO_TCP, SOCKET_TCP_NODELAY, ADR(bOptNoDelay), SIZEOF(bOptNoDelay));

sa.sin_family:=SOCKET_AF_INET;
sa.sin_addr:=GetIPAddress(stIPAddress);
IF sa.sin_addr <> SOCKET_INADDR_NONE THEN
    sa.sin_port:=SysSockHtons(iPort);
    IF SysSockConnect(diSocket, ADR(sa), SIZEOF(sa)) = FALSE THEN
        SysSockClose(diSocket);
        diSocket:=SOCKET_INVALID;
    END_IF
ELSE
    SysSockClose(diSocket);
    diSocket:=SOCKET_INVALID;
END_IF

END_IF
TcpClientOpenSocket:=diSocket;
(*******)
FUNCTION TcpReceiveData : DINT
( Receive data from a tcp socket.
Return: Number of bytes received
)
VAR_INPUT
diSocket:DINT; ( Socket Id )
pbyData:DWORD; ( Address of data buffer )
diDataSize:DINT; ( Size of data to send )
diTImeout : DINT; ( Timeout in seconds )
END_VAR
VAR
fdRead:SOCKET_FD_SET;
tvTimeout:SOCKET_TIMEVAL;
rr:DINT;

END_VAR

tvTimeout.tv_usec := 0;
fdRead.fd_count := 1;
fdRead.fd_array[0] := diSocket;

IF (SysSockSelect(SOCKET_FD_SETSIZE, ADR(fdRead), 0, 0, ADR(tvTimeout)) > 0) THEN
TcpReceiveData:=SysSockRecv(diSocket, pbyData, diDataSize, 0);
END_IF

(*******)
FUNCTION TcpSendData : DINT
( Send data via TCP socket.
Return: Number of bytes sent
)
VAR_INPUT
diSocket:DINT; ( Socket Id )
pbyData:DWORD; ( Address of data buffer )
diDataSize:DINT; ( Size of data to send )
diTImeout : DINT; ( Timeout in seconds )
END_VAR
VAR
fdWrite:SOCKET_FD_SET;
tvTimeout:SOCKET_TIMEVAL;
END_VAR
tvTimeout.tv_sec := diTimeout ;
tvTimeout.tv_usec := 0;
fdWrite.fd_count := 1;
fdWrite.fd_array[0] := diSocket;
IF (SysSockSelect(SOCKET_FD_SETSIZE, 0, ADR(fdWrite), 0, ADR(tvTimeout)) > 0) THEN
TcpSendData:=SysSockSend(diSocket, pbyData, diDataSize, 0);
END_IF

(*******)

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