Re: Modbus Module issue

["Dmitry Yu. Bolkhovityanov via Tech-talk" <tech-talk at aps.anl.gov>]

Hi Luis!

Have you tried running Wireshark to see what happens on the Ethernet?



On Fri, 24 Jul 2026, Luis Alberto De Sousa Moreira via Tech-talk wrote:

> Hi Guys,
> I think I tried everything I can think off. Still no connection.
> May AI assistant thinks that the issue is that the module was built using 
> MinGW instead of the MSVC tool chain, it is talking about the fact that MinGW 
> uses a "Translation Layer" (POSIX vs. Winsock). I never had any issues before 
> so can't see that being the issue, but wondering what you thoughts are on 
> this.
> Kind Regards
>                  Luis
>
> On 24/07/2026 10:46, Luis Alberto De Sousa Moreira via Tech-talk wrote:
> >  Hi J?rn,
> >  I think we getting the wires crossed here... the OPCUA port is 4840 but
> >  the 502 port is the normal Modbus port.
> >  I managed to connect fine to it with other applications in the same
> >  machine.
> >
> >
> >
> >
> >  Kind Regards
> >                    Luis
> >
> >
> >  On 24/07/2026 10:38, J?rn Dreyer wrote:
> > >  Hi Luis,
> > >
> > >  are you sure you are using the correct port?
> > >  The Beckhoff documentation tells that the OPCUA server is listening on
> > >  port 4840.  Did you cahnge that when installing the OPCUA Sever on the
> > >  PLC?
> > >  The Ports 500 + x are normally used for the various NC applications in
> > >  your PLC program.
> > >
> > >  Regards
> > >
> > >  J?rn
> > >
> > >  Am Freitag, 24. Juli 2026, 09:57:38 Mitteleurop?ische Sommerzeit schrieb
> > >  Luis Alberto De Sousa Moreira via Tech-talk:
> > > >  Just found another application I used before as a Modbus client, called
> > > >  EasyModbusClient.
> > > >  It connects fine and gets data.
> > > >
> > > >  This is getting more intriguing...
> > > >
> > > >  Best Regards
> > > >                      Luis
> > > >
> > > >  On 24/07/2026 09:40, Luis Alberto De Sousa Moreira via Tech-talk wrote:
> > > > >  Hi Gabriel,
> > > > >  The firewall seems to be the culprit, but I added rules for the
> > > > >  application. I also just done a test where I disabled the firewall and
> > > > >  I get the same result.
> > > > >
> > > > >  D:\FalconDev\EPICS\modbus\iocBoot\iocTest>..\..\bin\windows-x64-mingw\modbusApp.exe
> > > > >  BPS_Beck.cmd
> > > > > #  BPS_Beck.cmd
> > > > > #  Just testing the modbus module with my BPS Beckhoff PLC.
> > > > > #  1. Cleanly lock network routing automatically at boot
> > > > >  epicsEnvSet("EPICS_CA_ADDR_LIST", "10.136.0.255")
> > > > >  epicsEnvSet("EPICS_CA_AUTO_ADDR_LIST", "NO")
> > > > >  epicsEnvSet("EPICS_CAS_INTF_ADDR_LIST", "10.136.0.34")
> > > > >  # gvl.mb_Input_Registers[10] := GVL.d_setpoint_T1;              // T1
> > > > >                    mS
> > > > >  # gvl.mb_Input_Registers[11] := GVL.d_setpoint_TRamp1;  // Ramp1
> > > > >           uS
> > > > >  # gvl.mb_Input_Registers[12] := GVL.d_setpoint_v1;              // V1
> > > > >                    10V
> > > > >  # gvl.mb_Input_Registers[13] := GVL.d_setpoint_T2;              // T2
> > > > >                    mS
> > > > >  # gvl.mb_Input_Registers[14] := GVL.d_setpoint_TRamp2;  // Ramp2
> > > > >           uS
> > > > >  # gvl.mb_Input_Registers[15] := GVL.d_setpoint_V2;              // V2
> > > > >                    10V
> > > > >  # gvl.mb_Input_Registers[16] := GVL.d_setpoint_T3;              // T3
> > > > >                    mS
> > > > >  # gvl.mb_Input_Registers[17] := GVL.d_setpoint_TRamp3;  // Ramp3
> > > > >           uS
> > > > >  # gvl.mb_Input_Registers[18] := GVL.d_setpoint_V3;              // V3
> > > > >                    10V
> > > > >  # gvl.mb_Input_Registers[19] := GVL.d_setpoint_pulseLength;     //
> > > > >  PulseLength  S /mS
> > > > >  # gvl.mb_Input_Registers[20] := GVL.d_setpoint_TRampDown;       //
> > > > >  RampDown             uS
> > > > >  dbLoadDatabase("../../dbd/modbusApp.dbd")
> > > > >  modbusApp_registerRecordDeviceDriver(pdbbase)
> > > > >  # Get the connection going
> > > > >  drvAsynIPPortConfigure("BPS_Beck", "10.136.0.30:502", 0, 0, 0)
> > > > >  2026/07/24 09:32:59.953 BPS_Beck -1 autoConnect could not connect:
> > > > >  Can't connect to 10.136.0.30:502: Unknown error
> > > > >  # drvAsynIPPortConfigure("BPS_Beck", "8.8.8.8:8080", 0, 0, 0)
> > > > >  modbusInterposeConfig("BPS_Beck", 0, 5000, 0)
> > > > >  asynSetOption("BPS_Beck",0, "disconnectOnReadTimeout", "Y")
> > > > >  #
> > > > >  =========================================================================
> > > > > #  Configure Modbus Drivers Memory Blocks
> > > > > #
> > > > >  =========================================================================
> > > > > #  Syntax:
> > > > > #  drvModbusAsynConfigure("portName", "tcpPortName", slaveAddress,
> > > > >  modbusFunction, modbusStartAddress, modbusLength, dataType, pollMsec,
> > > > >  "plcType")
> > > > >  # drvModbusAsynConfigure("modbusPortName", "asynPortName",
> > > > >  slaveAddress, modbusFunction, startAddress, length, dataType,
> > > > >  pollMsec, "plcType")
> > > > > #  Read Coils (Function Code 1)
> > > > > #  Reads 16 binary bits starting at offset 0, polling every 200
> > > > >  milliseconds.
> > > > >  # drvModbusAsynConfigure("READ_COILS", "PLC_NET", 0, 1, 0, 1, 0, 200,
> > > > >  "OldPLC")
> > > > > #  Write Coils (Function Code 5)
> > > > > #  Configures a write-only path for coils. pollMsec is 0 because writes
> > > > >  are instantaneous.
> > > > >  # drvModbusAsynConfigure("WRITE_COILS", "PLC_NET", 0, 5, 0, 1, 0, 0,
> > > > >  "OldPLC")
> > > > >  # Reads 11 read-only 16-bit registers starting at offset 10, polling
> > > > >  every 500 milliseconds.
> > > > >  # dataType=0 specifies standard 16-bit unsigned integers (UINT_16).
> > > > >  drvModbusAsynConfigure("READ_INPUTS", "BPS_Beck", 1, 4, 10, 11, 0,
> > > > >  500, "Beckhoff")
> > > > > #  Read Holding Registers (Function Code 3)
> > > > > #  Reads 1 read/write 16-bit register starting at offset 0, polling
> > > > >  every 500 milliseconds.
> > > > > #  dataType=0 specifies standard 16-bit unsigned integers (UINT_16).
> > > > > #  drvModbusAsynConfigure("READ_HOLDING", "PLC_NET", 0, 3, 0, 1, 0,
> > > > >  500, "OldPLC")
> > > > > #  Block E: Write Holding Registers (Function Code 6)
> > > > > #  Configures a write-only path for single registers. pollMsec is 0 for
> > > > >  on-demand writing.
> > > > >  # drvModbusAsynConfigure("WRITE_HOLDING", "PLC_NET", 0, 6, 0, 1, 0, 0,
> > > > >  "OldPLC")
> > > > > #  Enable ASYN_TRACEIO_HEX on octet server
> > > > > #  asynSetTraceIOMask("BPS_Beck",0,4)
> > > > > #  Enable ASYN_TRACE_ERROR and ASYN_TRACEIO_DRIVER on octet server
> > > > > #  asynSetTraceMask("BPS_Beck",0,9)
> > > > >  dbLoadRecords("../../db/BPS_Beck.db")
> > > > >  iocInit
> > > > >  Starting iocInit
> > > > >  ############################################################################
> > > > >  ## EPICS R7.0.10
> > > > >  ## Rev. 2026-07-01T08:47+0200
> > > > >  ## Rev. Date build date/time:
> > > > >  ############################################################################
> > > > >  2026/07/24 09:33:00.992 drvModbusAsyn::doModbusIO port READ_INPUTS
> > > > >  error calling writeRead, error=asynManager::queueLockPort queueRequest
> > > > >  failed: port BPS_Beck not connected, nwrite=0/6, nread=0
> > > > >  iocRun: All initialization complete
> > > > >  epics>
> > > > >
> > > > >  Kind Regards
> > > > >                    Luis
> > > > >
> > > > >
> > > > >
> > > > >  On 23/07/2026 16:24, Gabriel Fedel wrote:
> > > > > >  Hi Luis,
> > > > > >
> > > > > >  Couldn't the firewall be blocking  the EPICS application ?
> > > > > >
> > > > > >  Best Regards
> > > > > >  Gabriel
> > > > > >  ------------------------------------------------------------------------
> > > > > >  *From:* Tech-talk<tech-talk-bounces at aps.anl.gov> on behalf of Luis
> > > > > >  Alberto De Sousa Moreira via Tech-talk<tech-talk at aps.anl.gov>
> > > > > >  *Sent:* Thursday, July 23, 2026 3:59 PM
> > > > > >  *To:* Mark Rivers<rivers at cars.uchicago.edu>;tech-talk at aps.anl.gov
> > > > > >  <tech-talk at aps.anl.gov>
> > > > > >  *Subject:* Re: Modbus Module issue
> > > > > >  Hi Mark,
> > > > > >  My other application is using the Modbus protocol, I used it to do the
> > > > > >  initial testing on my system.
> > > > > >  I tried the telnet command from my MSYS2 environment and it can
> > > > > >  connect...
> > > > > >
> > > > > >  telnet 10.136.0.30 502
> > > > > >  Trying 10.136.0.30...
> > > > > >  Connected to 10.136.0.30.
> > > > > >  Escape character is '^]'.
> > > > > >
> > > > > >  Kind Regards
> > > > > >                      Luis
> > > > > >
> > > > > >  On 23/07/2026 15:31, Mark Rivers wrote:
> > > > > > >  telnet 10.136.0.30 502
> >  --
> >  Luis Moreira
> >  EPFL SB SPC-II, PPH241 (Batiment PPH) Station 13
> >  CH-1015 Lausanne, Switzerland
> >  Tel.    (+41) 21 693 58 37
> >  E-Mailluis.moreira at epfl.ch
	_________________________________________
	  Dmitry Yu. Bolkhovityanov
	  The Budker Institute of Nuclear Physics
	  Novosibirsk, Russia